INDY-1883: add documentation for Message Requests #1027
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Signed-off-by: toktar <renata.toktar@dsr-corporation.com>
Signed-off-by: toktar <renata.toktar@dsr-corporation.com>
docs/message_requests.md
Outdated
| @@ -0,0 +1,30 @@ | |||
| # Message Requests | |||
|
|
|||
| In BFT protocols you can lose no more than a certain count of messages. But it may happen in following valid cases: | |||
docs/message_requests.md
Outdated
| @@ -0,0 +1,30 @@ | |||
| # Message Requests | |||
|
|
|||
| In BFT protocols you can lose no more than a certain count of messages. But it may happen in following valid cases: | |||
There was a problem hiding this comment.
In Plenum it may happen in the following valid cases
docs/message_requests.md
Outdated
|
|
||
| ###Three-phase commit messages | ||
|
|
||
| If a node lost a lot of messages for three-phase commit, ordering can stop for ever for this node. The problem is successfully solved via message request mechanism. |
There was a problem hiding this comment.
ordering can stop for this node until a catch-up is triggered by a checkpoint.
docs/message_requests.md
Outdated
|
|
||
| If a node lost a lot of messages for three-phase commit, ordering can stop for ever for this node. The problem is successfully solved via message request mechanism. | ||
| A node requests lost messages from other nodes in follow cases: | ||
| - A node received not next PrePrepare -> ask PrePrepares, Prepares, Commits from the node last pp_seq_no to received PrePrepare (pp_seq_no - 1) |
There was a problem hiding this comment.
All PrePrepares need to be applied sequentially, without any gaps. If a node receives a PrePrepare where previous PrePrepare(s) are not received yet (lost?), it asks .....
docs/message_requests.md
Outdated
| If a node lost a lot of messages for three-phase commit, ordering can stop for ever for this node. The problem is successfully solved via message request mechanism. | ||
| A node requests lost messages from other nodes in follow cases: | ||
| - A node received not next PrePrepare -> ask PrePrepares, Prepares, Commits from the node last pp_seq_no to received PrePrepare (pp_seq_no - 1) | ||
| - A node received not next Prepare -> ask PrePrepares for pp_seq_no from received Prepare |
There was a problem hiding this comment.
A node receives a Prepare for which it doesn't have the corresponding PrePrepare.
docs/message_requests.md
Outdated
| A node requests lost messages from other nodes in follow cases: | ||
| - A node received not next PrePrepare -> ask PrePrepares, Prepares, Commits from the node last pp_seq_no to received PrePrepare (pp_seq_no - 1) | ||
| - A node received not next Prepare -> ask PrePrepares for pp_seq_no from received Prepare | ||
| - A node received PrePrepare for not finalized request -> ask Propagates for not finalize requests from PrePrepare |
There was a problem hiding this comment.
A node receives a PrePrepare for a not finalized request (that is request for which the Node doesn't have a quorum of Propagates)
docs/message_requests.md
Outdated
|
|
||
| Lost messages may delay catchup for a long time. The node message requests mechanism is used in follow cases: | ||
| - A node requests a LedgerStatus in a start of catchup process to compare with self ledger. | ||
| - With the first message request for a LedgerStatus the node is scheduling a new message request in config.LedgerStatusTimeout for case the answer to the first request will not be received. |
There was a problem hiding this comment.
the answer to the first request is not received.
docs/message_requests.md
Outdated
| - A node requests a LedgerStatus in a start of catchup process to compare with self ledger. | ||
| - With the first message request for a LedgerStatus the node is scheduling a new message request in config.LedgerStatusTimeout for case the answer to the first request will not be received. | ||
| - A node requests a ConsistencyProof with median rate of ledger size on other nodes. | ||
| - With the first message request for a ConsistencyProof the node is scheduling a new message request in config.ConsistencyProofTimeout for case the answer to the first request will not be received. |
There was a problem hiding this comment.
the answer to the first request is not received.
docs/message_requests.md
Outdated
|
|
||
| If a node lost a lot of messages for three-phase commit, ordering can stop for ever for this node. The problem is successfully solved via message request mechanism. | ||
| A node requests lost messages from other nodes in follow cases: | ||
| - A node received not next PrePrepare -> ask PrePrepares, Prepares, Commits from the node last pp_seq_no to received PrePrepare (pp_seq_no - 1) |
There was a problem hiding this comment.
If the number of messages to be requested is more than CHK_FREQ, that is the size of Checkpoint, then nothing is requested since the Node is falling behind and is going to start a catch-up in any case because of a quorum of stashed stable checkpoints.
Signed-off-by: toktar <renata.toktar@dsr-corporation.com>
ashcherbakov
approved these changes
Dec 13, 2018
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
No description provided.