diff --git a/yang-mod-ver/draft-verdt-netmod-yang-module-versioning.txt b/yang-mod-ver/draft-verdt-netmod-yang-module-versioning.txt index fd2ed71..fcc6634 100644 --- a/yang-mod-ver/draft-verdt-netmod-yang-module-versioning.txt +++ b/yang-mod-ver/draft-verdt-netmod-yang-module-versioning.txt @@ -6,14 +6,14 @@ Network Working Group B. Claise Internet-Draft J. Clarke Updates: 7950 (if approved) R. Rahman Intended status: Standards Track R. Wilton, Ed. -Expires: December 5, 2019 Cisco Systems, Inc. +Expires: December 6, 2019 Cisco Systems, Inc. B. Lengyel Ericsson J. Sterne Nokia K. D'Souza AT&T - June 3, 2019 + June 4, 2019 Updated YANG Module Revision Handling @@ -21,10 +21,13 @@ Expires: December 5, 2019 Cisco Systems, Inc. Abstract - This document specifies a new YANG module update procedure to allow - for limited non-backwards-compatible changes, as an alternative - proposal to module update rules in the YANG 1.1 specifications. This - document updates RFC 7950, RFC 8407 and RFC 8525. + This document specifies a new YANG module update procedure that can + document when non-backwards-compatible changes have occurred during + the evolution of a YANG module. It provides a variant to the YANG + import statement to better represent inter-module dependencies. It + provides help and guidelines for managing the lifecycle of YANG + modules and individual schema nodes. This document updates RFC 7950, + RFC 8407 and RFC 8525. Status of This Memo @@ -41,23 +44,27 @@ Status of This Memo time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on December 5, 2019. + This Internet-Draft will expire on December 6, 2019. + -Copyright Notice - Copyright (c) 2019 IETF Trust and the persons identified as the - document authors. All rights reserved. - This document is subject to BCP 78 and the IETF Trust's Legal - Provisions Relating to IETF Documents -Claise, et al. Expires December 5, 2019 [Page 1] + +Claise, et al. Expires December 6, 2019 [Page 1] -Internet-Draft YANG Module Versioning June 2019 +Internet-Draft Updated YANG Module Revision Handling June 2019 + + +Copyright Notice + Copyright (c) 2019 IETF Trust and the persons identified as the + document authors. All rights reserved. + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect @@ -69,28 +76,28 @@ Internet-Draft YANG Module Versioning June 2019 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 1.1. Updates to YANG RFCs . . . . . . . . . . . . . . . . . . 3 + 1.1. Updates to YANG RFCs . . . . . . . . . . . . . . . . . . 4 2. Refinements to YANG revision handling . . . . . . . . . . . . 4 2.1. Updating a YANG module with a new revision . . . . . . . 4 2.1.1. Backwards-compatible changes . . . . . . . . . . . . 5 2.1.2. Non-backwards-compatible changes . . . . . . . . . . 5 2.2. nbc-changes revision extension statement . . . . . . . . 5 - 2.3. Revision label . . . . . . . . . . . . . . . . . . . . . 6 + 2.3. Revision-label . . . . . . . . . . . . . . . . . . . . . 6 2.4. YANG status description extension . . . . . . . . . . . . 6 - 2.5. Examples for updating the YANG module revision history . 6 + 2.5. Examples for updating the YANG module revision history . 7 3. Import by derived revision . . . . . . . . . . . . . . . . . 9 3.1. Module import examples . . . . . . . . . . . . . . . . . 10 4. Updates to ietf-yang-library . . . . . . . . . . . . . . . . 12 - 4.1. Advertising revision label . . . . . . . . . . . . . . . 12 + 4.1. Advertising revision-label . . . . . . . . . . . . . . . 12 4.2. Resolving ambiguous module imports . . . . . . . . . . . 12 - 4.3. Reporting how deprecated and obsolete nodes are handled . 12 + 4.3. Reporting how deprecated and obsolete nodes are handled . 13 5. Versioning of YANG instance data . . . . . . . . . . . . . . 13 - 6. Guidelines for using the YANG module update rules . . . . . . 13 - 6.1. Guidelines for YANG module authors . . . . . . . . . . . 13 + 6. Guidelines for using the YANG module update rules . . . . . . 14 + 6.1. Guidelines for YANG module authors . . . . . . . . . . . 14 6.1.1. Making non-backwards-compatible changes to a YANG module . . . . . . . . . . . . . . . . . . . . . . . 14 6.2. Versioning Considerations for Clients . . . . . . . . . . 15 - 7. Module Versioning Extension YANG Modules . . . . . . . . . . 15 + 7. Module Versioning Extension YANG Modules . . . . . . . . . . 16 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 21 9. Security Considerations . . . . . . . . . . . . . . . . . . . 22 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 @@ -99,21 +106,21 @@ Table of Contents 11.1. Normative References . . . . . . . . . . . . . . . . . . 23 11.2. Informative References . . . . . . . . . . . . . . . . . 23 Appendix A. Appendix . . . . . . . . . . . . . . . . . . . . . . 25 - A.1. Open Issues . . . . . . . . . . . . . . . . . . . . . . . 25 - A.2. Examples of guidelines for making non-backwards- - compatible changes to a YANG module . . . . . . . . . . . 25 - A.2.1. Removing a data node . . . . . . . . . . . . . . . . 26 - A.2.2. Changing the type of a leaf node . . . . . . . . . . 26 - A.2.3. Reducing the range of a leaf node . . . . . . . . . . 27 - A.2.4. Changing the key of a list . . . . . . . . . . . . . 28 -Claise, et al. Expires December 5, 2019 [Page 2] +Claise, et al. Expires December 6, 2019 [Page 2] -Internet-Draft YANG Module Versioning June 2019 +Internet-Draft Updated YANG Module Revision Handling June 2019 + A.1. Open Issues . . . . . . . . . . . . . . . . . . . . . . . 25 + A.2. Examples of guidelines for making non-backwards- + compatible changes to a YANG module . . . . . . . . . . . 26 + A.2.1. Removing a data node . . . . . . . . . . . . . . . . 26 + A.2.2. Changing the type of a leaf node . . . . . . . . . . 27 + A.2.3. Reducing the range of a leaf node . . . . . . . . . . 28 + A.2.4. Changing the key of a list . . . . . . . . . . . . . 28 A.2.5. Renaming a node . . . . . . . . . . . . . . . . . . . 29 A.2.6. Changing a default value . . . . . . . . . . . . . . 30 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 @@ -123,8 +130,8 @@ Internet-Draft YANG Module Versioning June 2019 This document defines a solution to the YANG module lifecycle problems described in [I-D.verdt-netmod-yang-versioning-reqs]. Complementary documents provide a complete solution to the YANG - versioning requirements, with the overall relationship of the drafts - described in [I-D.verdt-netmod-yang-solutions]. + versioning requirements, with the overall relationship of the + solution drafts described in [I-D.verdt-netmod-yang-solutions]. Specifically, this document recognises a need (within standards organizations, vendors, and the industry) to sometimes allow YANG @@ -145,7 +152,7 @@ Internet-Draft YANG Module Versioning June 2019 Updates and augmentations to ietf-yang-library to include the revision label in the module descriptions, to report how - 'deprecated' and 'obsolete' nodes are handled by a server, and to + "deprecated" and "obsolete" nodes are handled by a server, and to clarify how module imports are resolved when multiple versions could otherwise be chosen. @@ -154,6 +161,15 @@ Internet-Draft YANG Module Versioning June 2019 Guidelines for how the YANG module update rules defined in this document should be used, along with examples. + + + + +Claise, et al. Expires December 6, 2019 [Page 3] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + Open issues are listed at Appendix A.1, and tracked at . @@ -163,13 +179,6 @@ Internet-Draft YANG Module Versioning June 2019 YANG revision handling and update rules, and Section 3 describes an extension to do import by derived revision. - - -Claise, et al. Expires December 5, 2019 [Page 3] - -Internet-Draft YANG Module Versioning June 2019 - - This document updates [RFC8525]. Section 4 defines how a client of a YANG library datastore schema chooses which revision of an import- only module is used to resolve a module import when the definition is @@ -186,7 +195,7 @@ Internet-Draft YANG Module Versioning June 2019 to have two independent revisions of a YANG module that are both directly derived from the same parent revision. - This document clarifies [RFC7950] to explictly allow non linear + This document clarifies [RFC7950] to explicitly allow non linear development of YANG module revisions, so modules MAY have multiple revisions that directly derive from the same parent revision. As per [RFC7950], YANG module revisions continue to be uniquely identified @@ -194,10 +203,10 @@ Internet-Draft YANG Module Versioning June 2019 MUST have unique revision dates. [RFC7950] chapter 11 requires that all updates to a YANG module are - backwards compatible to the previous revision of the module. This + backwards-compatible to the previous revision of the module. This document allows for more flexible evolution of YANG modules: Non- backwards-compatible changes between module revisions are allowed and - are documented using a new 'nbc-changes' extension statement in the + are documented using a new "nbc-changes" extension statement in the module revision history. 2.1. Updating a YANG module with a new revision @@ -208,31 +217,30 @@ Internet-Draft YANG Module Versioning June 2019 Where pragmatic, updates to YANG modules SHOULD be backwards- compatible, following the definition in Section 2.1.1. - A new module revision MAY contain non-backwards-compatible changes, - i.e., the semantics of an existing definition MAY be changed in a - non-backwards-compatible way without requiring a new definition with - a new identifier. A new module revision with non-backwards- - compatible changes MUST include a 'rev:nbc-changes' extension - substatement to signal the potential for incompatibility to existing - module users and readers. - - -Claise, et al. Expires December 5, 2019 [Page 4] +Claise, et al. Expires December 6, 2019 [Page 4] -Internet-Draft YANG Module Versioning June 2019 +Internet-Draft Updated YANG Module Revision Handling June 2019 + + A new module revision MAY contain non-backwards-compatible changes, + i.e., the semantics of an existing definition MAY be changed in a + non-backwards-compatible way without requiring a new definition with + a new identifier. A new module revision with non-backwards- + compatible changes MUST include a "rev:nbc-changes" extension + substatement to signal the potential for incompatibility to existing + module users and readers. 2.1.1. Backwards-compatible changes The following statements update [RFC7950] chapter 11 to define what - changes constitute an allowable backwards-compatible change to a YANG + constitutes an allowable backwards-compatible change to a YANG module: - o A "status" "deprecated" statement may be added, or changed from + o A "status" "deprecated" statement MAY be added, or changed from "current" to "deprecated", but adding or changing "status" to "obsolete" is not a backwards-compatible change. @@ -244,53 +252,55 @@ Internet-Draft YANG Module Versioning June 2019 o In statements that have any data definition statements as substatements, those data definition substatements MAY be - reordered, as long as they do not change the ordering or any 'rpc' - 'input' substatements. If new data definition statements are + reordered, as long as they do not change the ordering or any "rpc" + "input" substatements. If new data definition statements are added, they can be added anywhere in the sequence of existing substatements. 2.1.2. Non-backwards-compatible changes - Any changes to YANG modules that are not classified by Section 2.1.1 - as being backwards-compatible are classified as 'non-backwards- - compatible' changes. + Any changes to YANG modules that are not defined by Section 2.1.1 as + being backwards-compatible are classified as "non-backwards- + compatible" changes. One particular change to [RFC7950] chapter 11 is that adding or - changing a 'status' state to 'obsolete' is classified as a non- + changing a "status" state to "obsolete" is classified as a non- backwards-compatible change, because it could break any clients - relying on servers implementing the obsoleted data node. + relying on servers implementing the obsolete data node. 2.2. nbc-changes revision extension statement - The 'rev:nbc-changes' extension statement is used to indicate YANG + The "rev:nbc-changes" extension statement is used to indicate YANG module revisions that contain non-backwards-compatible changes. - If a a revision of a YANG module contains changes, relative to the - preceding revision in the revision history, that do not conform to - the module update rules defined in Section 2.1.1, then a 'rev:nbc- - changes' extension statement MUST be added to a sub-statement to the - revision statement. - Conversely, if a revision does not contain an 'rev:nbc-changes' - extension substatement then all changes, relative to the preceding - revision in the revision history MUST be backwards-compatible. -Claise, et al. Expires December 5, 2019 [Page 5] +Claise, et al. Expires December 6, 2019 [Page 5] -Internet-Draft YANG Module Versioning June 2019 +Internet-Draft Updated YANG Module Revision Handling June 2019 + + If a revision of a YANG module contains changes, relative to the + preceding revision in the revision history, that do not conform to + the module update rules defined in Section 2.1.1, then a "rev:nbc- + changes" extension statement MUST be added as a substatement to the + "revision" statement. + + Conversely, if a revision does not contain an "rev:nbc-changes" + extension substatement then all changes, relative to the preceding + revision in the revision history, MUST be backwards-compatible. -2.3. Revision label +2.3. Revision-label - Each revision entry in a module may have a 'revision label' - associated with it. The label can be used to provide an additional + Each revision entry in a module MAY have a revision-label associated + with it. The revision-label can be used to provide an additional versioning identifier associated with the revision. E.g., one option for a versioning scheme that could be used is [TODO - Reference semver draft]. - If a revision has an associated revision label, then it may be used + If a revision has an associated revision-label, then it may be used instead of the revision date in the following places: In an "rev:revision-or-derived" extension statement argument. @@ -301,14 +311,33 @@ Internet-Draft YANG Module Versioning June 2019 2.4. YANG status description extension - The ietf-yang-revision module specifies the YANG extension 'status- - description' that can be used as a substatement of the status + The ietf-yang-revision module specifies the YANG extension "status- + description" that can be used as a substatement of the status statement. The argument to this extension can contain freeform text to help readers of the module understand why the node was deprecated or made obsolete, when it is anticipated that the node will no longer be available for use, and potentially reference other schema elements that can be used instead. An example is shown below. + + + + + + + + + + + + + + +Claise, et al. Expires December 6, 2019 [Page 6] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + leaf imperial-temperature { type int64; units "degrees Fahrenheit"; @@ -326,21 +355,11 @@ Internet-Draft YANG Module Versioning June 2019 The following diagram, explanation, and module history illustrates how the branched revision history, nbc-changes annotations, and - revision label could be used: - - - - - - -Claise, et al. Expires December 5, 2019 [Page 6] - -Internet-Draft YANG Module Versioning June 2019 - + revision-label could be used: Example YANG module with branched revision history. - Module Revision-date Revision label + Module Revision-date Revision-label 2019-01-01 <- 1.0.0 | 2019-02-01 <- 2.0.0 @@ -353,7 +372,7 @@ Internet-Draft YANG Module Versioning June 2019 | 2019-06-01 <- 3.1.0 - The tree diagram above illustrates how an example modules version + The tree diagram above illustrates how an example module's version history might evolve, over time. For example, the tree might represent the following changes, listed in chronological order from oldest revision to newest: @@ -370,29 +389,12 @@ Internet-Draft YANG Module Versioning June 2019 - - - - - - - - - - - - - - - - - - - -Claise, et al. Expires December 5, 2019 [Page 7] +Claise, et al. Expires December 6, 2019 [Page 7] -Internet-Draft YANG Module Versioning June 2019 +Internet-Draft Updated YANG Module Revision Handling June 2019 + + Example module, revision 2019-06-01: module example-module { @@ -405,24 +407,24 @@ Internet-Draft YANG Module Versioning June 2019 "to be completed"; revision 2019-06-01 { - rev:label "3.1.0"; + rev:revision-label "3.1.0"; rev:nbc-changes; description "Add new functionality."; } revision 2019-04-01 { - rev:label "3.0.0"; + rev:revision-label "3.0.0"; description "Add new functionality. Remove some deprecated nodes."; } revision 2019-02-01 { - rev:label "2.0.0"; + rev:revision-label "2.0.0"; rev:nbc-changes; description "Apply bugfix to pattern statement"; } revision 2019-01-01 { - rev:label "1.0.0"; + rev:revision-label "1.0.0"; description "Initial revision"; } @@ -443,12 +445,12 @@ Internet-Draft YANG Module Versioning June 2019 - - -Claise, et al. Expires December 5, 2019 [Page 8] +Claise, et al. Expires December 6, 2019 [Page 8] -Internet-Draft YANG Module Versioning June 2019 +Internet-Draft Updated YANG Module Revision Handling June 2019 + + Example module, revision 2019-05-01: module example-module { @@ -461,23 +463,23 @@ Internet-Draft YANG Module Versioning June 2019 "to be completed"; revision 2019-05-01 { - rev:label "2.2.0"; - description "Backwards compatible bugfix to enhancement."; + rev:revision-label "2.2.0"; + description "Backwards-compatible bugfix to enhancement."; } revision 2019-03-01 { - rev:label "2.1.0"; + rev:revision-label "2.1.0"; description "Apply enhancement to older release train."; } revision 2019-02-01 { - rev:label "2.0.0"; + rev:revision-label "2.0.0"; rev:nbc-changes; description "Apply bugfix to pattern statement"; } revision 2019-01-01 { - rev:label "1.0.0"; + rev:revision-label "1.0.0"; description "Initial revision"; } @@ -485,7 +487,7 @@ Internet-Draft YANG Module Versioning June 2019 3. Import by derived revision - RFC 7950 allows YANG module 'import' statements to optionally require + RFC 7950 allows YANG module "import" statements to optionally require the imported module to have a particular revision date. In practice, importing a module with an exact revision date is often too restrictive because it requires the importing module to be updated @@ -494,146 +496,149 @@ Internet-Draft YANG Module Versioning June 2019 statement is also not ideal because the importing module may not work with all possible revisions of the imported module. - Instead, it is desirable for a importing module to specify a 'minimum - required revision' of a module that it is compatible with, based on - the assumption that later revisions derived from that 'minimum - required revision' are also likely to be compatible. Many possible + Instead, it is desirable for a importing module to specify a "minimum + required revision" of a module that it is compatible with, based on -Claise, et al. Expires December 5, 2019 [Page 9] +Claise, et al. Expires December 6, 2019 [Page 9] -Internet-Draft YANG Module Versioning June 2019 +Internet-Draft Updated YANG Module Revision Handling June 2019 + the assumption that later revisions derived from that "minimum + required revision" are also likely to be compatible. Many possible changes to a YANG module do not break importing modules, even if the - changes themselves are not strictly backwards compatible. E.g., + changes themselves are not strictly backwards-compatible. E.g., fixing an incorrect pattern statement or description for a leaf would not break an import, changing the name of a leaf could break an import but frequently would not, but removing a container would break imports if that container is augmented by another module. - The ietf-revisions module defines the 'revision-or-derived' - extension, a substatement to the YANG 'import' statement, to allow - for a 'minium required revision' to be specified during import: + The ietf-revisions module defines the "revision-or-derived" + extension, a substatement to the YANG "import" statement, to allow + for a "minium required revision" to be specified during import: - The argument to the 'revision-or-derived' extension statement is a + The argument to the "revision-or-derived" extension statement is a revision-date or a revision-label. A particular revision of an imported module satisfies an import's - 'revision-or-derived' extension statement if the imported module's + "revision-or-derived" extension statement if the imported module's revision history contains a revision statement with a matching revision-date or revision-label. - An 'import' statement MUST NOT contain both a 'revision-or- - derived' extension statement and a 'revision-date' statement. + An "import" statement MUST NOT contain both a "revision-or- + derived" extension statement and a "revision-date" statement. - Using the 'revision-date' statement causes overly strict import + Using the "revision-date" statement causes overly strict import dependencies between modules and SHOULD NOT be used. - The 'revision-or-derived' extension statement MAY be specified + The "revision-or-derived" extension statement MAY be specified multiple times, allowing the import to use any module revision - that satifies at least one of the 'revision-or-derived' extension + that satifies at least one of the "revision-or-derived" extension statements. - The 'revision-or-derived' extension statement does not gaurantee + The "revision-or-derived" extension statement does not gaurantee that all module revisions that satisfy an import statement are necessarily compatible, it only gives an indication that the revisions are more likely to be compatible. Hence, non-backwards- compatible changes to an imported module may also require new revisions of any importing modules, updated to accommodation those - changes, along with updated import 'revision-or-derived' extension + changes, along with updated import "revision-or-derived" extension statements to depend on the updated imported module revision. 3.1. Module import examples - Consider an example module "example-module" that is hypothetically - available in the following versions: 0.1.0, 0.2.0, 1.0.0, 1.1.0, - 1.1.1m, 1.1.2M, 1.2.0, 1.2.1M, 1.2.2M, 1.3.0, 1.3.1, 2.0.0, 3.0.0, - and 3.1.0. E.g. matching the versions illustrated in Section 2.5. - + Consider the example module "example-module" from Section 2.5 that is + hypothetically available in the following revision/label pairings: + 2019-01-01/1.0.0, 2019-02-01/2.0.0, 2019-03-01/3.0.0, + 2019-04-01/2.1.0, 2019-05-01/2.2.0 and 2019-06-01/3.1.0. The + relationship between the revisions is as before: - - -Claise, et al. Expires December 5, 2019 [Page 10] +Claise, et al. Expires December 6, 2019 [Page 10] -Internet-Draft YANG Module Versioning June 2019 - +Internet-Draft Updated YANG Module Revision Handling June 2019 - The first example selects the specific version 1.1.2M. A specific - version import might be used if 1.1.2M contained changes that are - incompatible with other versions. - import example-module { - rev:revision-or-derived 2019-01-01; - } + Module Revision-date Revision-label + 2019-01-01 <- 1.0.0 + | + 2019-02-01 <- 2.0.0 + | \ + 2019-03-01 \ <- 3.0.0 + | \ + | 2019-04-01 <- 2.1.0 + | | + | 2019-05-01 <- 2.2.0 + | + 2019-06-01 <- 3.1.0 - The next example selects module versions that match, or are greater - than, version 1.2.0. This form may be used if there is a dependency - on a data node introduced in version 1.2.0. This is expected to be - the most commonly used form of 'import by version'. + The first example selects module revisions that match, or are derived + from the revision 2019-02-01. E.g., this dependency might be used if + there was a new container added in revision 2019-02-01 that is + augmented by the importing module. - Includes versions: 1.2.0, 1.2.1M, 1.2.2M, 1.3.0, 1.3.1, 2.0.0, 3.0.0 - and 3.1.0. + Includes revisions/labels: 2019-02-01/2.0.0, 2019-03-01/3.0.0, + 2019-04-01/2.1.0, 2019-05-01/2.2.0 and 2019-06-01/3.1.0. import example-module { - semver:version 1.2.0+; + ver:revision-or-derived 2019-02-01; } - The next example selects module versions that match, or are greater - than 1.1.0, but excluding all 1.1.x and 1.2.x 'M' versions. This - form may be needed if structural non backwards compatible changes are - introduced in a patch 'M' version. Generally, it is advisable to - avoid making such changes. - - Includes versions: 1.1.0, 1.1.1m, 1.2.0, 1.3.0, 1.3.1, 2.0.0, 3.0.0, - and 3.1.0. + Alternatively, the first example could have used the revision label + "1.0.0" instead, which selects the same set of revisions/versions. import example-module { - semver:version 1.1.0-1.1.1; - semver:version 1.2.0; - semver:version 1.3.0+; + ver:revision-or-derived 1.0.0; } - The last example selects all module versions with a major version - number of 1. This form may be useful if significant non backwards - compatible changes have been introduced in version 2.0.0 that break - import backwards compatibility. + The next example selects module revisions that are derived from + 2019-04-01 by using the revision label 2.1.0. - Includes versions: 1.0.0, 1.1.0, 1.1.1m, 1.1.2M, 1.2.0, 1.2.1M, - 1.2.2M, 1.3.0 and 1.3.1. + Includes revisions/labels: 2019-04-01/2.1.0 and 2019-05-01/2.2.0. + Even though 2019-06-01/3.1.0 has a higher revision label version + number than 2019-04-01/2.1.0 it is not a derived revision, and hence + it is not a valid revision for import. import example-module { - semver:version 1.0.0-1.MAX.MAX; + ver:revision-or-derived 2.1.0; } + The last example selects revisions derived from either 2019-04-01 or + 2019-06-01. It includes revisions/labels: 2019-04-01/2.1.0, + 2019-05-01/2.2.0, and 2019-06-01/3.1.0. -Claise, et al. Expires December 5, 2019 [Page 11] +Claise, et al. Expires December 6, 2019 [Page 11] -Internet-Draft YANG Module Versioning June 2019 +Internet-Draft Updated YANG Module Revision Handling June 2019 + import example-module { + ver:revision-or-derived 2019-04-01; + ver:revision-or-derived 2019-06-01; + } + 4. Updates to ietf-yang-library YANG library [RFC7895] [RFC8525] is modified to support the new module update rules in three ways. -4.1. Advertising revision label +4.1. Advertising revision-label - The ietf-yang-revisions YANG module augments the 'module' list in - ietf-yang-library with a 'revision-label' leaf to optionally declare - the revision label associated wth the particular revsion of each + The ietf-yang-revisions YANG module augments the "module" list in + ietf-yang-library with a "revision-label" leaf to optionally declare + the revision-label associated wth the particular revsion of each module. 4.2. Resolving ambiguous module imports A YANG datastore schema, defined in [RFC8525], can specify multiple - revisions of a YANG module in the schema using the 'import-only' + revisions of a YANG module in the schema using the "import-only" list, with the requirement from [RFC7950] that only a single revision of a YANG module may be implemented. @@ -648,7 +653,7 @@ Internet-Draft YANG Module Versioning June 2019 If a module import statement could resolve to more than one module revision defined in the datastore schema, and one of those revisions - is implemented (i.e., not an 'import-only' module), then the import + is implemented (i.e., not an "import-only" module), then the import statement MUST resolve to the revision of the module that is defined as being implemented by the datastore schema. @@ -657,39 +662,43 @@ Internet-Draft YANG Module Versioning June 2019 are implemented, then the import MUST resolve to the module revision with the latest revision date. -4.3. Reporting how deprecated and obsolete nodes are handled - The ietf-yang-revisions YANG module augments YANG library with two - leaves to allow a server to report how it handles status 'deprecated' - and status 'obsolete' nodes. The leaves are: - deprecated-nodes-implemented: If present, this leaf indicates that - all schema nodes with a status 'deprecated' child statement are - implemented equivalently as if they had status 'current', or -Claise, et al. Expires December 5, 2019 [Page 12] + + +Claise, et al. Expires December 6, 2019 [Page 12] -Internet-Draft YANG Module Versioning June 2019 +Internet-Draft Updated YANG Module Revision Handling June 2019 + +4.3. Reporting how deprecated and obsolete nodes are handled + + The ietf-yang-revisions YANG module augments YANG library with two + leaves to allow a server to report how it handles status "deprecated" + and status "obsolete" nodes. The leaves are: + deprecated-nodes-implemented: If present, this leaf indicates that + all schema nodes with a status "deprecated" child statement are + implemented equivalently as if they had status "current", or otherwise deviations MUST be used to explicitly remove - 'deprecated' nodes from the schema. If this leaf is absent then + "deprecated" nodes from the schema. If this leaf is absent then the behavior is unspecified. obsolete-nodes-absent: If present, this leaf indicates that the - server does not implement any status 'obsolete' nodes. If this + server does not implement any status "obsolete" nodes. If this leaf is absent then the behaviour is unspecified. - Servers SHOULD set both the 'deprecated-nodes-implemented' and - 'obsolete-nodes-absent' leaves. + Servers SHOULD set both the "deprecated-nodes-implemented" and + "obsolete-nodes-absent" leaves. - If a server does not set the 'deprecated-nodes-implemented' leaf, + If a server does not set the "deprecated-nodes-implemented" leaf, then clients MUST NOT rely solely on the "XXX - NBC Annotation" to - determine whether two module revisions are backwards compatible, and + determine whether two module revisions are backwards-compatible, and MUST also consider whether the status of any nodes has changed to - 'deprecated' and whether those nodes are implemented by the server. + "deprecated" and whether those nodes are implemented by the server. 5. Versioning of YANG instance data @@ -699,7 +708,7 @@ Internet-Draft YANG Module Versioning June 2019 However, instance data specifies the content-schema of the data-set. This schema SHOULD make use of versioning using revision dates and/or - revision labels for the individual YANG modules that comprise the + revision-labels for the individual YANG modules that comprise the schema or potentially for the entire schema itself (e.g., [I-D.rwilton-netmod-yang-packages] ). @@ -709,6 +718,18 @@ Internet-Draft YANG Module Versioning June 2019 of the YANG schema, or other revisions of the modules that define the schema. + + + + + + + +Claise, et al. Expires December 6, 2019 [Page 13] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + 6. Guidelines for using the YANG module update rules 6.1. Guidelines for YANG module authors @@ -722,24 +743,16 @@ Internet-Draft YANG Module Versioning June 2019 impact on clients and YANG module authors SHOULD try to mitigate that impact. - - - -Claise, et al. Expires December 5, 2019 [Page 13] - -Internet-Draft YANG Module Versioning June 2019 - - 6.1.1. Making non-backwards-compatible changes to a YANG module There are various valid situations where a YANG module has to be modified in a non-backwards-compatible way. Here are the different ways in which this can be done: - o NBC changes can be done incrementally using the 'deprecated' + o NBC changes can be done incrementally using the "deprecated" status to provide clients time to adapt to NBC changes. - o NBC changes are done at once, i.e. without using 'status' + o NBC changes are done at once, i.e. without using "status" statements. This has a big impact on clients. o If the server can support multiple versions of the YANG module or @@ -747,11 +760,11 @@ Internet-Draft YANG Module Versioning June 2019 [I-D.rwilton-netmod-yang-packages]), and allows the client to select the version (as per [I-D.wilton-netmod-yang-ver-selection]), then NBC changes MAY be - done without using 'status' statements. Clients would be required + done without using "status" statements. Clients would be required to select the version which they support and the NBC change would have no impact on them - Here are some guidelines on how non-backwards compatible changes can + Here are some guidelines on how non-backwards-compatible changes can be made incrementally: 1. The changes should be made gradually, e.g. a data node's status @@ -765,6 +778,14 @@ Internet-Draft YANG Module Versioning June 2019 2. A node with status "deprecated" MUST be supported for the solution described here to function properly. + + + +Claise, et al. Expires December 6, 2019 [Page 14] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + 3. A node with status "deprecated" SHOULD be available for at least one year before its status is changed to "obsolete", see Section 4.7 of [RFC8407]. @@ -778,14 +799,6 @@ Internet-Draft YANG Module Versioning June 2019 6. For status "deprecated", the "status-description" SHOULD also indicate until when support for the node is guaranteed. If there is a replacement data node, rpc, action or notification for the - - - -Claise, et al. Expires December 5, 2019 [Page 14] - -Internet-Draft YANG Module Versioning June 2019 - - deprecated node, this SHOULD be stated in the "status- description". @@ -822,6 +835,13 @@ Internet-Draft YANG Module Versioning June 2019 timely fashion. When a node's status changes to "obsolete", clients MUST stop using that node. + + +Claise, et al. Expires December 6, 2019 [Page 15] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + 7. Module Versioning Extension YANG Modules YANG module with extensions for defining a module's YANG semantic @@ -834,14 +854,6 @@ Internet-Draft YANG Module Versioning June 2019 prefix rev; organization - - - -Claise, et al. Expires December 5, 2019 [Page 15] - -Internet-Draft YANG Module Versioning June 2019 - - "IETF NETMOD (Network Modeling) Working Group"; contact "WG Web: @@ -879,6 +891,13 @@ Internet-Draft YANG Module Versioning June 2019 Revision Handling"; } + + +Claise, et al. Expires December 6, 2019 [Page 16] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + typedef revision-identifier { type string { pattern '\d{4}-\d{2}-\d{2}'; @@ -890,14 +909,6 @@ Internet-Draft YANG Module Versioning June 2019 typedef label-string { type string { - - - -Claise, et al. Expires December 5, 2019 [Page 16] - -Internet-Draft YANG Module Versioning June 2019 - - length "1..255"; pattern '[^\s@]+'; pattern '\d{4}-\d{2}-\d{2}' { @@ -909,7 +920,7 @@ Internet-Draft YANG Module Versioning June 2019 Excludes spaces and '@'. Cannot match revision-date."; reference - "draft-verdt-netmod-yang-module-versioning: Revision label"; + "draft-verdt-netmod-yang-module-versioning: Revision-label"; } typedef revision-date-or-label { @@ -918,7 +929,7 @@ Internet-Draft YANG Module Versioning June 2019 type label-string; } description - "Represents either a YANG revision-date or a revision label"; + "Represents either a YANG revision-date or a revision-label"; } extension nbc-changes { @@ -935,6 +946,14 @@ Internet-Draft YANG Module Versioning June 2019 the 'nbc-changes' statement MUST be added as a substatement to the revision statement. + + + +Claise, et al. Expires December 6, 2019 [Page 17] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + Conversely, if a revision of a YANG module only contains changes, relative to the preceding revision in the revision history, that are classified as 'backwards-compatible' then @@ -945,15 +964,7 @@ Internet-Draft YANG Module Versioning June 2019 extension statement"; } - extension label { - - - -Claise, et al. Expires December 5, 2019 [Page 17] - -Internet-Draft YANG Module Versioning June 2019 - - + extension revision-label { argument label-string; description "The label can be used to provide an additional versioning @@ -961,11 +972,11 @@ Internet-Draft YANG Module Versioning June 2019 a versioning scheme that could be used is [TODO - Reference semver draft]. - Each 'revision' statement MAY have a single 'label' + Each 'revision' statement MAY have a single 'revision-label' substatement."; reference - "draft-verdt-netmod-module-versioning: Revision label"; + "draft-verdt-netmod-module-versioning: Revision-label"; } extension revision-or-derived { @@ -991,6 +1002,14 @@ Internet-Draft YANG Module Versioning June 2019 A particular revision of an imported module satisfies an import's 'revision-or-derived' extension statement if the imported module's revision history contains a revision + + + +Claise, et al. Expires December 6, 2019 [Page 18] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + statement with a matching revision-date or revision-label. The 'revision-or-derived' extension statement does not @@ -1002,14 +1021,6 @@ Internet-Draft YANG Module Versioning June 2019 reference "draft-verdt-netmod-yang-module-versioning: Import by derived revision"; - - - -Claise, et al. Expires December 5, 2019 [Page 18] - -Internet-Draft YANG Module Versioning June 2019 - - } extension status-description { @@ -1048,6 +1059,13 @@ Internet-Draft YANG Module Versioning June 2019 prefix yanglib; } + + +Claise, et al. Expires December 6, 2019 [Page 19] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + organization "IETF NETMOD (Network Modeling) Working Group"; contact @@ -1058,14 +1076,6 @@ Internet-Draft YANG Module Versioning June 2019 Author: Joe Clarke - - - -Claise, et al. Expires December 5, 2019 [Page 19] - -Internet-Draft YANG Module Versioning June 2019 - - Author: Reshad Rahman @@ -1104,6 +1114,14 @@ Internet-Draft YANG Module Versioning June 2019 "The revision label associated with this module revision. The label MUST match the rev:label value in the specific revision of the module loaded in this module-set."; + + + +Claise, et al. Expires December 6, 2019 [Page 20] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + reference "draft-verdt-netmod-module-versioning: Updated YANG Module Revision Handling"; @@ -1114,14 +1132,6 @@ Internet-Draft YANG Module Versioning June 2019 description "Augmentations to the ietf-yang-library module to indicate how deprecated and obsoleted nodes are handled for each datastore - - - -Claise, et al. Expires December 5, 2019 [Page 20] - -Internet-Draft YANG Module Versioning June 2019 - - schema supported by the server."; leaf deprecated-nodes-implemented { @@ -1160,23 +1170,23 @@ Internet-Draft YANG Module Versioning June 2019 o Balazs Lengyel - o Benoit Claise - o Ebben Aries - o Jason Sterne - o Joe Clarke +Claise, et al. Expires December 6, 2019 [Page 21] + +Internet-Draft Updated YANG Module Revision Handling June 2019 - o Juergen Schoenwaelder + o Benoit Claise + o Ebben Aries + o Jason Sterne -Claise, et al. Expires December 5, 2019 [Page 21] - -Internet-Draft YANG Module Versioning June 2019 + o Joe Clarke + o Juergen Schoenwaelder o Mahesh Jethanandani @@ -1217,6 +1227,13 @@ Internet-Draft YANG Module Versioning June 2019 Reference: [RFCXXXX] + + +Claise, et al. Expires December 6, 2019 [Page 22] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + The ietf-yl-revisions module: Name: ietf-yl-revisions @@ -1227,13 +1244,6 @@ Internet-Draft YANG Module Versioning June 2019 Reference: [RFCXXXX] - - -Claise, et al. Expires December 5, 2019 [Page 22] - -Internet-Draft YANG Module Versioning June 2019 - - 11. References 11.1. Normative References @@ -1273,6 +1283,13 @@ Internet-Draft YANG Module Versioning June 2019 YANG Module Update Procedure", draft-clacla-netmod-yang- model-update-06 (work in progress), July 2018. + + +Claise, et al. Expires December 6, 2019 [Page 23] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + [I-D.claise-semver] Claise, B., Barnes, R., and J. Clarke, "Semantic Versioning and Structure for IETF Specifications", draft- @@ -1283,13 +1300,6 @@ Internet-Draft YANG Module Versioning June 2019 Format", draft-ietf-netmod-yang-instance-file-format-02 (work in progress), February 2019. - - -Claise, et al. Expires December 5, 2019 [Page 23] - -Internet-Draft YANG Module Versioning June 2019 - - [I-D.openconfig-netmod-model-catalog] Shaikh, A., Shakir, R., and K. D'Souza, "Catalog and registry for YANG models", draft-openconfig-netmod-model- @@ -1328,23 +1338,23 @@ Internet-Draft YANG Module Versioning June 2019 [4] https://github.com/netmod-wg/yang-ver-dt/issues/12 - [5] https://github.com/netmod-wg/yang-ver-dt/issues/10 - [6] https://github.com/netmod-wg/yang-ver-dt/issues/8 - [7] https://github.com/netmod-wg/yang-ver-dt/issues/6 - [8] https://github.com/netmod-wg/yang-ver-dt/issues/4 +Claise, et al. Expires December 6, 2019 [Page 24] + +Internet-Draft Updated YANG Module Revision Handling June 2019 - [9] https://github.com/netmod-wg/yang-ver-dt/issues/15 + [5] https://github.com/netmod-wg/yang-ver-dt/issues/10 + [6] https://github.com/netmod-wg/yang-ver-dt/issues/8 + [7] https://github.com/netmod-wg/yang-ver-dt/issues/6 -Claise, et al. Expires December 5, 2019 [Page 24] - -Internet-Draft YANG Module Versioning June 2019 + [8] https://github.com/netmod-wg/yang-ver-dt/issues/4 + [9] https://github.com/netmod-wg/yang-ver-dt/issues/15 [10] https://github.com/netmod-wg/yang-ver-dt/issues/2 @@ -1381,6 +1391,17 @@ A.1. Open Issues o Status obsolete nodes#2 [10] + + + + + + +Claise, et al. Expires December 6, 2019 [Page 25] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + A.2. Examples of guidelines for making non-backwards-compatible changes to a YANG module @@ -1393,21 +1414,12 @@ A.2. Examples of guidelines for making non-backwards-compatible changes o Modifying the description in a way that changes the semantic meaning of the data node. - - - - -Claise, et al. Expires December 5, 2019 [Page 25] - -Internet-Draft YANG Module Versioning June 2019 - - o Any changes that change or reduce the allowed value set of the data node, either through changes in the type definition, or the - addition or changes to 'must' statements, or changes in the + addition or changes to "must" statements, or changes in the description. - o Adding or modifying 'when' statements that reduce when the data + o Adding or modifying "when" statements that reduce when the data node is available in the schema. o Making the statement conditional on if-feature. @@ -1436,6 +1448,16 @@ A.2.1. Removing a data node 2. Clients which require the data node select the older module revision + + + + + +Claise, et al. Expires December 6, 2019 [Page 26] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + A.2.2. Changing the type of a leaf node Changing the type of a leaf-node. e.g. consider a "vpn-id" node of @@ -1450,14 +1472,6 @@ A.2.2. Changing the type of a leaf node "current" and its description explains that it is replacing node "vpn-id". - - - -Claise, et al. Expires December 5, 2019 [Page 26] - -Internet-Draft YANG Module Versioning June 2019 - - 3. During the period of time where both nodes are available, how the server behaves when either node is set is outside the scope of this document and will vary on a case by case basis. Here are @@ -1492,6 +1506,14 @@ Internet-Draft YANG Module Versioning June 2019 2. New node "vpn-name" is added to the same location as described above. + + + +Claise, et al. Expires December 6, 2019 [Page 27] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + 3. Clients which require the data node select the older module revision @@ -1505,15 +1527,6 @@ A.2.3. Reducing the range of a leaf node Reducing the range of values of a leaf-node. e.g. consider a "vpn-id" node of type integer being changed from type uint32 to type uint16: - - - - -Claise, et al. Expires December 5, 2019 [Page 27] - -Internet-Draft YANG Module Versioning June 2019 - - 1. If all values which are being removed were never supported, e.g. if a vpn-id of 65536 or higher was never accepted, this is a backwards-compatible change for the functionality (no @@ -1548,6 +1561,15 @@ A.2.4. Changing the key of a list 3. During the period of time where both lists are available, how the server behaves when either list is set is outside the scope of + + + + +Claise, et al. Expires December 6, 2019 [Page 28] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + this document and will vary on a case by case basis. Here are some options: @@ -1563,13 +1585,6 @@ A.2.4. Changing the key of a list changed to "obsolete" and the "status-description" is updated. This is a non-backwards-compatible change. - - -Claise, et al. Expires December 5, 2019 [Page 28] - -Internet-Draft YANG Module Versioning June 2019 - - If the server can support NBC versions of the YANG module simultaneously using version selection, then the changes can be done immediately: @@ -1603,6 +1618,14 @@ A.2.5. Renaming a node 1. A server could prevent the new node from being set if the old node is already set (and vice-versa). The new node could + + + +Claise, et al. Expires December 6, 2019 [Page 29] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + have a when statement to achieve this. The old node must not have a when statement since this would be a non-backwards- compatible change, but the server could reject the old node @@ -1618,14 +1641,6 @@ A.2.5. Renaming a node changed to "obsolete" and the "status-description" is updated. This is a non-backwards-compatible change. - - - -Claise, et al. Expires December 5, 2019 [Page 29] - -Internet-Draft YANG Module Versioning June 2019 - - If the server can support NBC versions of the YANG module simultaneously using version selection, then the changes can be done immediately: @@ -1661,6 +1676,12 @@ Authors' Addresses Email: jclarke@cisco.com + +Claise, et al. Expires December 6, 2019 [Page 30] + +Internet-Draft Updated YANG Module Revision Handling June 2019 + + Reshad Rahman Cisco Systems, Inc. @@ -1673,15 +1694,6 @@ Authors' Addresses Email: rwilton@cisco.com - - - - -Claise, et al. Expires December 5, 2019 [Page 30] - -Internet-Draft YANG Module Versioning June 2019 - - Balazs Lengyel Ericsson Magyar Tudosok Korutja @@ -1721,16 +1733,4 @@ Internet-Draft YANG Module Versioning June 2019 - - - - - - - - - - - - -Claise, et al. Expires December 5, 2019 [Page 31] +Claise, et al. Expires December 6, 2019 [Page 31] diff --git a/yang-mod-ver/draft-verdt-netmod-yang-module-versioning.xml b/yang-mod-ver/draft-verdt-netmod-yang-module-versioning.xml index 5da3a41..2e2d5d7 100644 --- a/yang-mod-ver/draft-verdt-netmod-yang-module-versioning.xml +++ b/yang-mod-ver/draft-verdt-netmod-yang-module-versioning.xml @@ -23,7 +23,7 @@ -Updated YANG Module Revision Handling +Updated YANG Module Revision Handling @@ -112,9 +112,12 @@ - This document specifies a new YANG module update procedure to allow - for limited non-backwards-compatible changes, as an alternative - proposal to module update rules in the YANG 1.1 specifications. This + This document specifies a new YANG module update procedure that + can document when non-backwards-compatible changes have occurred + during the evolution of a YANG module. It provides a variant to + the YANG import statement to better represent inter-module + dependencies. It provides help and guidelines for managing the + lifecycle of YANG modules and individual schema nodes. This document updates RFC 7950, RFC 8407 and RFC 8525. @@ -122,7 +125,7 @@
This document defines a solution to the YANG module lifecycle problems described in . Complementary documents provide a complete solution to the YANG - versioning requirements, with the overall relationship of the drafts described in . Specifically, this document recognises a need (within standards organizations, vendors, and the industry) to @@ -138,7 +141,7 @@ A YANG extension allowing YANG module imports to specify an earliest module revision that may satisfy the import dependency. Updates and augmentations to ietf-yang-library to include the revision label in the module descriptions, to - report how 'deprecated' and 'obsolete' nodes are handled by a server, and to clarify how module imports are resolved + report how "deprecated" and "obsolete" nodes are handled by a server, and to clarify how module imports are resolved when multiple versions could otherwise be chosen. Considerations of how versioning applies to YANG instance data. Guidelines for how the YANG module update rules defined in this document should be used, along with examples. @@ -165,14 +168,14 @@ strictly linear, i.e., it is prohibited to have two independent revisions of a YANG module that are both directly derived from the same parent revision. - This document clarifies to explictly allow non linear development of YANG module + This document clarifies to explicitly allow non linear development of YANG module revisions, so modules MAY have multiple revisions that directly derive from the same parent revision. As per , YANG module revisions continue to be uniquely identified by the module's revision-date, and hence all revisions of a module MUST have unique revision dates. - chapter 11 requires that all updates to a YANG module are backwards compatible to the + chapter 11 requires that all updates to a YANG module are backwards-compatible to the previous revision of the module. This document allows for more flexible evolution of YANG modules: - Non-backwards-compatible changes between module revisions are allowed and are documented using a new 'nbc-changes' + Non-backwards-compatible changes between module revisions are allowed and are documented using a new "nbc-changes" extension statement in the module revision history.
@@ -182,47 +185,47 @@ target="bc_update_rules"/>. A new module revision MAY contain non-backwards-compatible changes, i.e., the semantics of an existing definition MAY be changed in a non-backwards-compatible way without requiring a new definition with a new identifier. A new - module revision with non-backwards-compatible changes MUST include a 'rev:nbc-changes' extension substatement to + module revision with non-backwards-compatible changes MUST include a "rev:nbc-changes" extension substatement to signal the potential for incompatibility to existing module users and readers.
- The following statements update chapter 11 to define what changes constitute an + The following statements update chapter 11 to define what constitutes an allowable backwards-compatible change to a YANG module: - A "status" "deprecated" statement may be added, or changed from "current" to "deprecated", but adding or + A "status" "deprecated" statement MAY be added, or changed from "current" to "deprecated", but adding or changing "status" to "obsolete" is not a backwards-compatible change. Obsolete definitions MAY be removed from published modules, and are classified as backwards-compatible changes. In some circumstances it may be helpful to retain the obsolete definitions to ensure that their identifiers are not reused with a different meaning. In statements that have any data definition statements as substatements, those data definition substatements - MAY be reordered, as long as they do not change the ordering or any 'rpc' 'input' substatements. If new data + MAY be reordered, as long as they do not change the ordering or any "rpc" "input" substatements. If new data definition statements are added, they can be added anywhere in the sequence of existing substatements.
- Any changes to YANG modules that are not classified by as being - backwards-compatible are classified as 'non-backwards-compatible' changes. - One particular change to chapter 11 is that adding or changing a 'status' state to - 'obsolete' is classified as a non-backwards-compatible change, because it could break any clients relying on - servers implementing the obsoleted data node. + Any changes to YANG modules that are not defined by as being + backwards-compatible are classified as "non-backwards-compatible" changes. + One particular change to chapter 11 is that adding or changing a "status" state to + "obsolete" is classified as a non-backwards-compatible change, because it could break any clients relying on + servers implementing the obsolete data node.
- The 'rev:nbc-changes' extension statement is used to indicate YANG module revisions that contain + The "rev:nbc-changes" extension statement is used to indicate YANG module revisions that contain non-backwards-compatible changes. - If a a revision of a YANG module contains changes, relative to the preceding revision in the revision history, + If a revision of a YANG module contains changes, relative to the preceding revision in the revision history, that do not conform to the module update rules defined in , then a - 'rev:nbc-changes' extension statement MUST be added to a sub-statement to the revision statement. - Conversely, if a revision does not contain an 'rev:nbc-changes' extension substatement then all changes, relative - to the preceding revision in the revision history MUST be backwards-compatible. + "rev:nbc-changes" extension statement MUST be added as a substatement to the "revision" statement. + Conversely, if a revision does not contain an "rev:nbc-changes" extension substatement then all changes, relative + to the preceding revision in the revision history, MUST be backwards-compatible.
-
- Each revision entry in a module may have a 'revision label' associated with it. The label can be used to provide an +
+ Each revision entry in a module MAY have a revision-label associated with it. The revision-label can be used to provide an additional versioning identifier associated with the revision. E.g., one option for a versioning scheme that could be used is [TODO - Reference semver draft]. - If a revision has an associated revision label, then it may be used instead of the revision date in the following places: + If a revision has an associated revision-label, then it may be used instead of the revision date in the following places: In an "rev:revision-or-derived" extension statement argument. In the filename of a YANG module, where it takes the following form: @@ -232,7 +235,7 @@
- The ietf-yang-revision module specifies the YANG extension 'status-description' that can be used as a substatement of + The ietf-yang-revision module specifies the YANG extension "status-description" that can be used as a substatement of the status statement. The argument to this extension can contain freeform text to help readers of the module understand why the node was deprecated or made obsolete, when it is anticipated that the node will no longer be available for use, and potentially reference other schema elements that can be used instead. An example is shown @@ -259,11 +262,11 @@ leaf imperial-temperature {
The following diagram, explanation, and module history illustrates how the branched revision history, nbc-changes - annotations, and revision label could be used: + annotations, and revision-label could be used:
Example YANG module with branched revision history. - Module Revision-date Revision label + Module Revision-date Revision-label 2019-01-01 <- 1.0.0 | 2019-02-01 <- 2.0.0 @@ -277,12 +280,11 @@ leaf imperial-temperature { 2019-06-01 <- 3.1.0
- The tree diagram above illustrates how an example modules version - history might evolve, over time. For example, the tree might represent the - following changes, listed in chronological order from oldest - revision to newest: + The tree diagram above illustrates how an example module's version history might evolve, over time. For example, + the tree might represent the following changes, listed in chronological order from oldest revision to newest:
+ Example module, revision 2019-06-01: module example-module { @@ -295,24 +297,24 @@ leaf imperial-temperature { "to be completed"; revision 2019-06-01 { - rev:label "3.1.0"; + rev:revision-label "3.1.0"; rev:nbc-changes; description "Add new functionality."; } revision 2019-04-01 { - rev:label "3.0.0"; + rev:revision-label "3.0.0"; description "Add new functionality. Remove some deprecated nodes."; } revision 2019-02-01 { - rev:label "2.0.0"; + rev:revision-label "2.0.0"; rev:nbc-changes; description "Apply bugfix to pattern statement"; } revision 2019-01-01 { - rev:label "1.0.0"; + rev:revision-label "1.0.0"; description "Initial revision"; } @@ -320,6 +322,7 @@ leaf imperial-temperature {
+ Example module, revision 2019-05-01: module example-module { @@ -332,23 +335,23 @@ leaf imperial-temperature { "to be completed"; revision 2019-05-01 { - rev:label "2.2.0"; - description "Backwards compatible bugfix to enhancement."; + rev:revision-label "2.2.0"; + description "Backwards-compatible bugfix to enhancement."; } revision 2019-03-01 { - rev:label "2.1.0"; + rev:revision-label "2.1.0"; description "Apply enhancement to older release train."; } revision 2019-02-01 { - rev:label "2.0.0"; + rev:revision-label "2.0.0"; rev:nbc-changes; description "Apply bugfix to pattern statement"; } revision 2019-01-01 { - rev:label "1.0.0"; + rev:revision-label "1.0.0"; description "Initial revision"; } @@ -358,100 +361,116 @@ leaf imperial-temperature {
- RFC 7950 allows YANG module 'import' statements to optionally require the imported module to have a particular + RFC 7950 allows YANG module "import" statements to optionally require the imported module to have a particular revision date. In practice, importing a module with an exact revision date is often too restrictive because it requires the importing module to be updated whenever any change to the imported module occurs. The alternative choice of using an import statement without any revision date statement is also not ideal because the importing module may not work with all possible revisions of the imported module. - Instead, it is desirable for a importing module to specify a 'minimum required revision' of a module that it is - compatible with, based on the assumption that later revisions derived from that 'minimum required revision' are also + Instead, it is desirable for a importing module to specify a "minimum required revision" of a module that it is + compatible with, based on the assumption that later revisions derived from that "minimum required revision" are also likely to be compatible. Many possible changes to a YANG module do not break importing modules, even if the changes - themselves are not strictly backwards compatible. E.g., fixing an incorrect pattern statement or description for a + themselves are not strictly backwards-compatible. E.g., fixing an incorrect pattern statement or description for a leaf would not break an import, changing the name of a leaf could break an import but frequently would not, but removing a container would break imports if that container is augmented by another module. - The ietf-revisions module defines the 'revision-or-derived' extension, a substatement to the YANG 'import' - statement, to allow for a 'minium required revision' to be specified during import: + The ietf-revisions module defines the "revision-or-derived" extension, a substatement to the YANG "import" + statement, to allow for a "minium required revision" to be specified during import: - The argument to the 'revision-or-derived' extension statement is a revision-date or a revision-label. - A particular revision of an imported module satisfies an import's 'revision-or-derived' extension statement if + The argument to the "revision-or-derived" extension statement is a revision-date or a revision-label. + A particular revision of an imported module satisfies an import's "revision-or-derived" extension statement if the imported module's revision history contains a revision statement with a matching revision-date or revision-label. - An 'import' statement MUST NOT contain both a 'revision-or-derived' extension statement and a 'revision-date' + An "import" statement MUST NOT contain both a "revision-or-derived" extension statement and a "revision-date" statement. - Using the 'revision-date' statement causes overly strict import dependencies between modules and SHOULD NOT be + Using the "revision-date" statement causes overly strict import dependencies between modules and SHOULD NOT be used. - The 'revision-or-derived' extension statement MAY be specified multiple times, allowing the import to use any - module revision that satifies at least one of the 'revision-or-derived' extension statements. - The 'revision-or-derived' extension statement does not gaurantee that all module revisions that satisfy an import + The "revision-or-derived" extension statement MAY be specified multiple times, allowing the import to use any + module revision that satifies at least one of the "revision-or-derived" extension statements. + The "revision-or-derived" extension statement does not gaurantee that all module revisions that satisfy an import statement are necessarily compatible, it only gives an indication that the revisions are more likely to be compatible. Hence, non-backwards-compatible changes to an imported module may also require new revisions of any - importing modules, updated to accommodation those changes, along with updated import 'revision-or-derived' extension + importing modules, updated to accommodation those changes, along with updated import "revision-or-derived" extension statements to depend on the updated imported module revision.
- Consider an example module "example-module" that is - hypothetically available in the following versions: 0.1.0, 0.2.0, - 1.0.0, 1.1.0, 1.1.1m, 1.1.2M, 1.2.0, 1.2.1M, 1.2.2M, 1.3.0, 1.3.1, - 2.0.0, 3.0.0, and 3.1.0. E.g. matching the versions illustrated - in . - - The first example selects the specific version 1.1.2M. A - specific version import might be used if 1.1.2M contained changes - that are incompatible with other versions. -
- + Consider the example module "example-module" from that is hypothetically available in + the following revision/label pairings: 2019-01-01/1.0.0, + 2019-02-01/2.0.0, 2019-03-01/3.0.0, 2019-04-01/2.1.0, + 2019-05-01/2.2.0 and 2019-06-01/3.1.0. The relationship between + the revisions is as before: + +
+ + Module Revision-date Revision-label + 2019-01-01 <- 1.0.0 + | + 2019-02-01 <- 2.0.0 + | \ + 2019-03-01 \ <- 3.0.0 + | \ + | 2019-04-01 <- 2.1.0 + | | + | 2019-05-01 <- 2.2.0 + | + 2019-06-01 <- 3.1.0 + +
+ + The first example selects module revisions that match, or are + derived from the revision 2019-02-01. E.g., this dependency + might be used if there was a new container added in revision + 2019-02-01 that is augmented by the importing module. + Includes revisions/labels: 2019-02-01/2.0.0, 2019-03-01/3.0.0, + 2019-04-01/2.1.0, 2019-05-01/2.2.0 and 2019-06-01/3.1.0. +
+ import example-module { - rev:revision-or-derived 2019-01-01; + ver:revision-or-derived 2019-02-01; } - -
+ +
- The next example selects module versions that match, or are - greater than, version 1.2.0. This form may be used if there is a - dependency on a data node introduced in version 1.2.0. This is - expected to be the most commonly used form of 'import by version'. - Includes versions: 1.2.0, 1.2.1M, 1.2.2M, 1.3.0, 1.3.1, 2.0.0, - 3.0.0 and 3.1.0. -
- + Alternatively, the first example could have used the + revision label "1.0.0" instead, which selects the same set of + revisions/versions. +
+ import example-module { - semver:version 1.2.0+; + ver:revision-or-derived 1.0.0; } - -
- - The next example selects module versions that match, or are - greater than 1.1.0, but excluding all 1.1.x and 1.2.x 'M' - versions. This form may be needed if structural non backwards - compatible changes are introduced in a patch 'M' version. - Generally, it is advisable to avoid making such changes. - Includes versions: 1.1.0, 1.1.1m, 1.2.0, 1.3.0, 1.3.1, 2.0.0, - 3.0.0, and 3.1.0. -
- + +
+ + The next example selects module revisions that are derived + from 2019-04-01 by using the revision label 2.1.0. + Includes revisions/labels: 2019-04-01/2.1.0 and + 2019-05-01/2.2.0. Even though 2019-06-01/3.1.0 has a higher + revision label version number than 2019-04-01/2.1.0 it is not a + derived revision, and hence it is not a valid revision for + import. +
+ import example-module { - semver:version 1.1.0-1.1.1; - semver:version 1.2.0; - semver:version 1.3.0+; + ver:revision-or-derived 2.1.0; } - -
+ +
- The last example selects all module versions with a major version number of 1. This form may be useful if - significant non backwards compatible changes have been introduced in version 2.0.0 that break import backwards - compatibility. - Includes versions: 1.0.0, 1.1.0, 1.1.1m, 1.1.2M, 1.2.0, 1.2.1M, 1.2.2M, 1.3.0 and 1.3.1. -
- + The last example selects revisions derived from either + 2019-04-01 or 2019-06-01. It includes revisions/labels: + 2019-04-01/2.1.0, 2019-05-01/2.2.0, and 2019-06-01/3.1.0. +
+ import example-module { - semver:version 1.0.0-1.MAX.MAX; + ver:revision-or-derived 2019-04-01; + ver:revision-or-derived 2019-06-01; } - -
+ +
@@ -460,14 +479,14 @@ import example-module { YANG library is modified to support the new module update rules in three ways. -
- The ietf-yang-revisions YANG module augments the 'module' list in ietf-yang-library with a 'revision-label' leaf to - optionally declare the revision label associated wth the particular revsion of each module. +
+ The ietf-yang-revisions YANG module augments the "module" list in ietf-yang-library with a "revision-label" leaf to + optionally declare the revision-label associated wth the particular revsion of each module.
A YANG datastore schema, defined in , can specify multiple revisions of a YANG module - in the schema using the 'import-only' list, with the requirement from that only a single + in the schema using the "import-only" list, with the requirement from that only a single revision of a YANG module may be implemented. If a YANG module import statement does not specify a specific revision within the datastore schema then it could be ambiguous as to which module revision the import statement should resolve to. Hence, a datastore schema @@ -475,7 +494,7 @@ import example-module { actually used by the server. The following rules remove the ambiguity: If a module import statement could resolve to more than one module revision defined in the datastore schema, - and one of those revisions is implemented (i.e., not an 'import-only' module), then the import statement MUST + and one of those revisions is implemented (i.e., not an "import-only" module), then the import statement MUST resolve to the revision of the module that is defined as being implemented by the datastore schema. If a module import statement could resolve to more than one module revision defined in the datastore schema, and none of those revisions are implemented, then the import MUST resolve to the module revision with the latest @@ -483,20 +502,20 @@ import example-module {
The ietf-yang-revisions YANG module augments YANG library with two leaves to allow a server to report how it handles - status 'deprecated' and status 'obsolete' nodes. The leaves are: + status "deprecated" and status "obsolete" nodes. The leaves are: If present, this leaf indicates that all schema nodes with a - status 'deprecated' child statement are implemented equivalently as if they had status 'current', or otherwise - deviations MUST be used to explicitly remove 'deprecated' nodes from the schema. If this leaf is absent then + status "deprecated" child statement are implemented equivalently as if they had status "current", or otherwise + deviations MUST be used to explicitly remove "deprecated" nodes from the schema. If this leaf is absent then the behavior is unspecified. If present, this leaf indicates that the server does not implement any - status 'obsolete' nodes. If this leaf is absent then the behaviour is unspecified. + status "obsolete" nodes. If this leaf is absent then the behaviour is unspecified. - Servers SHOULD set both the 'deprecated-nodes-implemented' and 'obsolete-nodes-absent' leaves. - If a server does not set the 'deprecated-nodes-implemented' leaf, then clients MUST NOT rely solely on the "XXX - - NBC Annotation" to determine whether two module revisions are backwards compatible, and MUST also consider - whether the status of any nodes has changed to 'deprecated' and whether those nodes are implemented by the + Servers SHOULD set both the "deprecated-nodes-implemented" and "obsolete-nodes-absent" leaves. + If a server does not set the "deprecated-nodes-implemented" leaf, then clients MUST NOT rely solely on the "XXX + - NBC Annotation" to determine whether two module revisions are backwards-compatible, and MUST also consider + whether the status of any nodes has changed to "deprecated" and whether those nodes are implemented by the server.
@@ -506,7 +525,7 @@ import example-module { updated revision handling rules described in this document, as compatibility for instance data is undefined. However, instance data specifies the content-schema of the data-set. This schema SHOULD make use of versioning - using revision dates and/or revision labels for the individual YANG modules that comprise the schema or + using revision dates and/or revision-labels for the individual YANG modules that comprise the schema or potentially for the entire schema itself (e.g., ). In this way, the versioning of a content-schema associated with an instance data set, may help a client to @@ -524,12 +543,12 @@ import example-module { There are various valid situations where a YANG module has to be modified in a non-backwards-compatible way. Here are the different ways in which this can be done: - NBC changes can be done incrementally using the 'deprecated' status to provide clients time to adapt to NBC changes. - NBC changes are done at once, i.e. without using 'status' statements. This has a big impact on clients. - If the server can support multiple versions of the YANG module or of YANG packages(as specified in ), and allows the client to select the version (as per ), then NBC changes MAY be done without using 'status' statements. Clients would be required to select the version which they support and the NBC change would have no impact on them + NBC changes can be done incrementally using the "deprecated" status to provide clients time to adapt to NBC changes. + NBC changes are done at once, i.e. without using "status" statements. This has a big impact on clients. + If the server can support multiple versions of the YANG module or of YANG packages(as specified in ), and allows the client to select the version (as per ), then NBC changes MAY be done without using "status" statements. Clients would be required to select the version which they support and the NBC change would have no impact on them - Here are some guidelines on how non-backwards compatible changes can be made incrementally: + Here are some guidelines on how non-backwards-compatible changes can be made incrementally: The changes should be made gradually, e.g. a data node's status SHOULD NOT be changed directly from "current" to "obsolete" (see Section 4.7 of ), instead the status SHOULD first be @@ -683,27 +702,27 @@ module ietf-yang-revisions { extension statement"; } - extension label { + extension revision-label { argument label-string; description - "The label can be used to provide an additional versioning - identifier associated with the revision. E.g., one option for - a versioning scheme that could be used is [TODO - Reference - semver draft]. + "The revision-label can be used to provide an additional + versioning identifier associated with the revision. E.g., one + option for a versioning scheme that could be used is [TODO - + Reference semver draft]. - Each 'revision' statement MAY have a single 'label' + Each 'revision' statement MAY have a single 'revision-label' substatement."; reference - "draft-verdt-netmod-module-versioning: Revision label"; + "draft-verdt-netmod-module-versioning: Revision-label"; } extension revision-or-derived { argument revision-date-or-label; description "Restricts the revision of the module that may be imported to - one that matches or is derived from the specified revision - date or label. + one that matches or is derived from the specified + revision-date or revision-ñlabel. The argument value MUST conform to the 'revision-date-or-label' defined type. @@ -1004,8 +1023,8 @@ module ietf-yl-revisions { Changing the name, type, or units of a data node. Modifying the description in a way that changes the semantic meaning of the data node. Any changes that change or reduce the allowed value set of the data node, either through changes in the type - definition, or the addition or changes to 'must' statements, or changes in the description. - Adding or modifying 'when' statements that reduce when the data node is available in the schema. + definition, or the addition or changes to "must" statements, or changes in the description. + Adding or modifying "when" statements that reduce when the data node is available in the schema. Making the statement conditional on if-feature. diff --git a/yang-mod-ver/ietf-yang-revisions.yang b/yang-mod-ver/ietf-yang-revisions.yang index b292202..219d4b9 100644 --- a/yang-mod-ver/ietf-yang-revisions.yang +++ b/yang-mod-ver/ietf-yang-revisions.yang @@ -99,27 +99,27 @@ module ietf-yang-revisions { extension statement"; } - extension label { + extension revision-label { argument label-string; description - "The label can be used to provide an additional versioning - identifier associated with the revision. E.g., one option for - a versioning scheme that could be used is [TODO - Reference - semver draft]. + "The revision-label can be used to provide an additional + versioning identifier associated with the revision. E.g., one + option for a versioning scheme that could be used is [TODO - + Reference semver draft]. - Each 'revision' statement MAY have a single 'label' + Each 'revision' statement MAY have a single 'revision-label' substatement."; reference - "draft-verdt-netmod-module-versioning: Revision label"; + "draft-verdt-netmod-module-versioning: Revision-label"; } extension revision-or-derived { argument revision-date-or-label; description "Restricts the revision of the module that may be imported to - one that matches or is derived from the specified revision - date or label. + one that matches or is derived from the specified + revision-date or revision-ñlabel. The argument value MUST conform to the 'revision-date-or-label' defined type.