RFE: setting per-mount options via .meta #1785
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Type:Enhancement
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@csabahenk this is critical enhancement. This was one reason I was trying to have 'global' translator for every volume. More on this @ #303 I feel a global xlator is better because it can be controlled with cli in that case (for all clients). I would still like a meta overload because it helps in debugging in one particular mount point. |
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The .meta synthetic tree features the options entry for each xlator, which lets us see the options with which the translator was configured. Technically, 'options' exports the options dict with which the given xlator has been configured. This approach provides read-only access to the xlator options, and only those options are visible which has been set. We implement an alternative options entry (referred to as 'aadjustable options' in the sequel) that exports the full option set of the xlator. We extended the volume_options stucture wih 'fetch' and 'update' methods, that facilitate access to the realtime values of the xlator options. In the adjustable options dict each option is readable which has 'fetch' and if they have 'update' too, then they shall be writable (this is properly reflected in file modes since 2554080). While the dict-based options is generic and provides an export mechanism for xlator options without specific support from the xlators, adjustable options will export only those options for which the xlator implements fetch/update. We made this effort for the fuse xlator, which is positioned in glusterfs client as the root of the xlator tree, and thus can't be 'hot-swapped' like other xlators via graph switch. All the fuse options obained 'fetch'; and the ones where runtime update is possible also 'update' (ie. those which control the internal behavior of the filesystem server, can be updated; the ones which are mount options or init options for the FUSE infrastucture, can't). ** THIS IS A WIP implementation, misses one thing: adjustability of fuse dumping, which will need more specific support code due to the involvement of external resource ** Change-Id: I72cb0f3c2f93712cd08147a4ae2e076354d8d9d8 Fixes: gluster#1785 Signed-off-by: Csaba Henk <csaba@redhat.com>
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The .meta synthetic tree features the options entry for each xlator, which lets us see the options with which the translator was configured. Technically, 'options' exports the options dict with which the given xlator has been configured. This approach provides read-only access to the xlator options, and only those options are visible which has been set. We implement an alternative options entry (referred to as 'aadjustable options' in the sequel) that exports the full option set of the xlator. We extended the volume_options stucture wih 'fetch' and 'update' methods, that facilitate access to the realtime values of the xlator options. In the adjustable options dict each option is readable which has 'fetch' and if they have 'update' too, then they shall be writable (this is properly reflected in file modes since 2554080). While the dict-based options is generic and provides an export mechanism for xlator options without specific support from the xlators, adjustable options will export only those options for which the xlator implements fetch/update. We made this effort for the fuse xlator, which is positioned in glusterfs client as the root of the xlator tree, and thus can't be 'hot-swapped' like other xlators via graph switch. All the fuse options obained 'fetch'; and the ones where runtime update is possible also 'update' (ie. those which control the internal behavior of the filesystem server, can be updated; the ones which are mount options or init options for the FUSE infrastucture, can't). Change-Id: I72cb0f3c2f93712cd08147a4ae2e076354d8d9d8 Fixes: gluster#1785 Signed-off-by: Csaba Henk <csaba@redhat.com>
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Nov 27, 2021
The .meta synthetic tree features the options entry for each xlator, which lets us see the options with which the translator was configured. Technically, 'options' exports the options dict with which the given xlator has been configured. This approach provides read-only access to the xlator options, and only those options are visible which has been set. We implement an alternative options entry (referred to as 'aadjustable options' in the sequel) that exports the full option set of the xlator. We extended the volume_options stucture wih 'fetch' and 'update' methods, that facilitate access to the realtime values of the xlator options. In the adjustable options dict each option is readable which has 'fetch' and if they have 'update' too, then they shall be writable (this is properly reflected in file modes since 2554080). While the dict-based options is generic and provides an export mechanism for xlator options without specific support from the xlators, adjustable options will export only those options for which the xlator implements fetch/update. We made this effort for the fuse xlator, which is positioned in glusterfs client as the root of the xlator tree, and thus can't be 'hot-swapped' like other xlators via graph switch. All the fuse options obained 'fetch'; and the ones where runtime update is possible also 'update' (ie. those which control the internal behavior of the filesystem server, can be updated; the ones which are mount options or init options for the FUSE infrastucture, can't). Change-Id: I72cb0f3c2f93712cd08147a4ae2e076354d8d9d8 Fixes: gluster#1785 Signed-off-by: Csaba Henk <csaba@redhat.com>
csabahenk
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Nov 30, 2021
The .meta synthetic tree features the options entry for each xlator, which lets us see the options with which the translator was configured. Technically, 'options' exports the options dict with which the given xlator has been configured. This approach provides read-only access to the xlator options, and only those options are visible which has been set. We implement an alternative options entry (referred to as 'adjustable options' in the sequel) that exports the full option set of the xlator. We extended the volume_options stucture wih 'fetch' and 'update' methods, that facilitate access to the realtime values of the xlator options. In the adjustable options dict each option is readable which has 'fetch' and if they have 'update' too, then they shall be writable (this is properly reflected in file modes since 2554080). While the dict-based options is generic and provides an export mechanism for xlator options without specific support from the xlators, adjustable options will export only those options for which the xlator implements fetch/update. We made this effort for the fuse xlator, which is positioned in glusterfs client as the root of the xlator tree, and thus can't be 'hot-swapped' like other xlators via graph switch. All the fuse options obained 'fetch'; and the ones where runtime update is possible also 'update' (ie. those which control the internal behavior of the filesystem server, can be updated; the ones which are mount options or init options for the FUSE infrastucture, can't). Change-Id: I72cb0f3c2f93712cd08147a4ae2e076354d8d9d8 Fixes: gluster#1785 Signed-off-by: Csaba Henk <csaba@redhat.com>
csabahenk
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Nov 30, 2021
The .meta synthetic tree features the options entry for each xlator, which lets us see the options with which the translator was configured. Technically, 'options' exports the options dict with which the given xlator has been configured. This approach provides read-only access to the xlator options, and only those options are visible which has been set. We implement an alternative options entry (referred to as 'adjustable options' in the sequel) that exports the full option set of the xlator. We extended the volume_options stucture wih 'fetch' and 'update' methods, that facilitate access to the realtime values of the xlator options. In the adjustable options dict each option is readable which has 'fetch' and if they have 'update' too, then they shall be writable (this is properly reflected in file modes since 2554080). While the dict-based options is generic and provides an export mechanism for xlator options without specific support from the xlators, adjustable options will export only those options for which the xlator implements fetch/update. We made this effort for the fuse xlator, which is positioned in glusterfs client as the root of the xlator tree, and thus can't be 'hot-swapped' like other xlators via graph switch. All the fuse options obained 'fetch'; and the ones where runtime update is possible also 'update' (ie. those which control the internal behavior of the filesystem server, can be updated; the ones which are mount options or init options for the FUSE infrastucture, can't). Change-Id: I72cb0f3c2f93712cd08147a4ae2e076354d8d9d8 Fixes: gluster#1785 Signed-off-by: Csaba Henk <csaba@redhat.com>
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Thank you for your contributions. |
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Closing this issue as there was no update since my last update on issue. If this is an issue which is still valid, feel free to open it. |
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Problem
Options that affect a single mount can only be set as command line options (
--opt1 VAL1 --opt2 VAL2...style options for glusterfs, or-oopt1=VAL1,opt2=VAL2...style options for mount.glusterfs), and they are in effect for the whole lifetime of the mount. Such options includes ones that have both volume-level and mount-level variants (eg.diagnostics.client-log-levelvolume option ~--log-levelcommand line option) and most importantly, options for the fuse translator.This latter case is important because it sets apart the fuse xlator UI-wise: while options of other translators are possible to adjust at runtime via cli, fuse translator options can only be affected at mount time, via command line options. This is justified technically, as fuse is the fixed root of the xlator graph which is re-grafted upon a graph switch (that happens upon adjusting volume options at runtime), but weird from user's perspective; and not only weird, but thoroughly unpractical as several fuse options have a heavy impact on glusterfs behavior, and it's cumbersome that a remount is needed to adjust them (becoming an obstacle to getting diagnostical data and experimenting with flexible performance tuning).
Solution
The .meta tree
Glusterfs has a less known reflection facility, the .meta hidden (= readdir doesn't list it) subtree. Under this entry various live statistics are available. At this moment it's a read-only tree.
Plan
Export per mount (or at least fuse xlator) options in writable manner under .meta, similarly to how procfs / sysfs exposes various kernel tunables.
While the xlator option space will still remain divided — fuse options are per-mount and .meta tunable, other xlator options are per-volume and cli tunable —, which is probably not completely reasonable from user POV, it makes sense to have a split UI-wise between per-mount (.meta tunable) and per-volume (cli tunable) options. That is, if a user doesn't bother about how options are dispatched to particular xlators, then the UI split will make sense to her according to scope of the setting.
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