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Diffstat (limited to 'Documentation/git-maintenance.txt')
| -rw-r--r-- | Documentation/git-maintenance.txt | 147 |
1 files changed, 146 insertions, 1 deletions
diff --git a/Documentation/git-maintenance.txt b/Documentation/git-maintenance.txt index 6abcb8255a..6fec1eb8dc 100644 --- a/Documentation/git-maintenance.txt +++ b/Documentation/git-maintenance.txt @@ -29,6 +29,32 @@ Git repository. SUBCOMMANDS ----------- +register:: + Initialize Git config values so any scheduled maintenance will + start running on this repository. This adds the repository to the + `maintenance.repo` config variable in the current user's global + config and enables some recommended configuration values for + `maintenance.<task>.schedule`. The tasks that are enabled are safe + for running in the background without disrupting foreground + processes. ++ +The `register` subcomand will also set the `maintenance.strategy` config +value to `incremental`, if this value is not previously set. The +`incremental` strategy uses the following schedule for each maintenance +task: ++ +-- +* `gc`: disabled. +* `commit-graph`: hourly. +* `prefetch`: hourly. +* `loose-objects`: daily. +* `incremental-repack`: daily. +-- ++ +`git maintenance register` will also disable foreground maintenance by +setting `maintenance.auto = false` in the current repository. This config +setting will remain after a `git maintenance unregister` command. + run:: Run one or more maintenance tasks. If one or more `--task` options are specified, then those tasks are run in that order. Otherwise, @@ -36,6 +62,22 @@ run:: config options are true. By default, only `maintenance.gc.enabled` is true. +start:: + Start running maintenance on the current repository. This performs + the same config updates as the `register` subcommand, then updates + the background scheduler to run `git maintenance run --scheduled` + on an hourly basis. + +stop:: + Halt the background maintenance schedule. The current repository + is not removed from the list of maintained repositories, in case + the background maintenance is restarted later. + +unregister:: + Remove the current repository from background maintenance. This + only removes the repository from the configured list. It does not + stop the background maintenance processes from running. + TASKS ----- @@ -47,6 +89,21 @@ commit-graph:: `commit-graph-chain` file. They will be deleted by a later run based on the expiration delay. +prefetch:: + The `prefetch` task updates the object directory with the latest + objects from all registered remotes. For each remote, a `git fetch` + command is run. The refmap is custom to avoid updating local or remote + branches (those in `refs/heads` or `refs/remotes`). Instead, the + remote refs are stored in `refs/prefetch/<remote>/`. Also, tags are + not updated. ++ +This is done to avoid disrupting the remote-tracking branches. The end users +expect these refs to stay unmoved unless they initiate a fetch. With prefetch +task, however, the objects necessary to complete a later real fetch would +already be obtained, so the real fetch would go faster. In the ideal case, +it will just become an update to bunch of remote-tracking branches without +any object transfer. + gc:: Clean up unnecessary files and optimize the local repository. "GC" stands for "garbage collection," but this task performs many @@ -55,6 +112,39 @@ gc:: be disruptive in some situations, as it deletes stale data. See linkgit:git-gc[1] for more details on garbage collection in Git. +loose-objects:: + The `loose-objects` job cleans up loose objects and places them into + pack-files. In order to prevent race conditions with concurrent Git + commands, it follows a two-step process. First, it deletes any loose + objects that already exist in a pack-file; concurrent Git processes + will examine the pack-file for the object data instead of the loose + object. Second, it creates a new pack-file (starting with "loose-") + containing a batch of loose objects. The batch size is limited to 50 + thousand objects to prevent the job from taking too long on a + repository with many loose objects. The `gc` task writes unreachable + objects as loose objects to be cleaned up by a later step only if + they are not re-added to a pack-file; for this reason it is not + advisable to enable both the `loose-objects` and `gc` tasks at the + same time. + +incremental-repack:: + The `incremental-repack` job repacks the object directory + using the `multi-pack-index` feature. In order to prevent race + conditions with concurrent Git commands, it follows a two-step + process. First, it calls `git multi-pack-index expire` to delete + pack-files unreferenced by the `multi-pack-index` file. Second, it + calls `git multi-pack-index repack` to select several small + pack-files and repack them into a bigger one, and then update the + `multi-pack-index` entries that refer to the small pack-files to + refer to the new pack-file. This prepares those small pack-files + for deletion upon the next run of `git multi-pack-index expire`. + The selection of the small pack-files is such that the expected + size of the big pack-file is at least the batch size; see the + `--batch-size` option for the `repack` subcommand in + linkgit:git-multi-pack-index[1]. The default batch-size is zero, + which is a special case that attempts to repack all pack-files + into a single pack-file. + OPTIONS ------- --auto:: @@ -62,7 +152,18 @@ OPTIONS only if certain thresholds are met. For example, the `gc` task runs when the number of loose objects exceeds the number stored in the `gc.auto` config setting, or when the number of pack-files - exceeds the `gc.autoPackLimit` config setting. + exceeds the `gc.autoPackLimit` config setting. Not compatible with + the `--schedule` option. + +--schedule:: + When combined with the `run` subcommand, run maintenance tasks + only if certain time conditions are met, as specified by the + `maintenance.<task>.schedule` config value for each `<task>`. + This config value specifies a number of seconds since the last + time that task ran, according to the `maintenance.<task>.lastRun` + config value. The tasks that are tested are those provided by + the `--task=<task>` option(s) or those with + `maintenance.<task>.enabled` set to true. --quiet:: Do not report progress or other information over `stderr`. @@ -74,6 +175,50 @@ OPTIONS `maintenance.<task>.enabled` configured as `true` are considered. See the 'TASKS' section for the list of accepted `<task>` values. + +TROUBLESHOOTING +--------------- +The `git maintenance` command is designed to simplify the repository +maintenance patterns while minimizing user wait time during Git commands. +A variety of configuration options are available to allow customizing this +process. The default maintenance options focus on operations that complete +quickly, even on large repositories. + +Users may find some cases where scheduled maintenance tasks do not run as +frequently as intended. Each `git maintenance run` command takes a lock on +the repository's object database, and this prevents other concurrent +`git maintenance run` commands from running on the same repository. Without +this safeguard, competing processes could leave the repository in an +unpredictable state. + +The background maintenance schedule runs `git maintenance run` processes +on an hourly basis. Each run executes the "hourly" tasks. At midnight, +that process also executes the "daily" tasks. At midnight on the first day +of the week, that process also executes the "weekly" tasks. A single +process iterates over each registered repository, performing the scheduled +tasks for that frequency. Depending on the number of registered +repositories and their sizes, this process may take longer than an hour. +In this case, multiple `git maintenance run` commands may run on the same +repository at the same time, colliding on the object database lock. This +results in one of the two tasks not running. + +If you find that some maintenance windows are taking longer than one hour +to complete, then consider reducing the complexity of your maintenance +tasks. For example, the `gc` task is much slower than the +`incremental-repack` task. However, this comes at a cost of a slightly +larger object database. Consider moving more expensive tasks to be run +less frequently. + +Expert users may consider scheduling their own maintenance tasks using a +different schedule than is available through `git maintenance start` and +Git configuration options. These users should be aware of the object +database lock and how concurrent `git maintenance run` commands behave. +Further, the `git gc` command should not be combined with +`git maintenance run` commands. `git gc` modifies the object database +but does not take the lock in the same way as `git maintenance run`. If +possible, use `git maintenance run --task=gc` instead of `git gc`. + + GIT --- Part of the linkgit:git[1] suite |