On Tue, Jul 07, 2020 at 02:21:14PM +0000, Derrick Stolee via GitGitGadget wrote: > > This is a second attempt at redesigning Git's repository maintenance > patterns. The first attempt [1] included a way to run jobs in the background > using a long-lived process; that idea was rejected and is not included in > this series. A future series will use the OS to handle scheduling tasks. > > [1] > https://lore.kernel.org/git/pull.597.git.1585946894.gitgitgadget@xxxxxxxxx/ > > As mentioned before, git gc already plays the role of maintaining Git > repositories. It has accumulated several smaller pieces in its long history, > including: > > 1. Repacking all reachable objects into one pack-file (and deleting > unreachable objects). > 2. Packing refs. > 3. Expiring reflogs. > 4. Clearing rerere logs. > 5. Updating the commit-graph file. > > While expiring reflogs, clearing rererelogs, and deleting unreachable > objects are suitable under the guise of "garbage collection", packing refs > and updating the commit-graph file are not as obviously fitting. Further, > these operations are "all or nothing" in that they rewrite almost all > repository data, which does not perform well at extremely large scales. > These operations can also be disruptive to foreground Git commands when git > gc --auto triggers during routine use. > > This series does not intend to change what git gc does, but instead create > new choices for automatic maintenance activities, of which git gc remains > the only one enabled by default. > > The new maintenance tasks are: > > * 'commit-graph' : write and verify a single layer of an incremental > commit-graph. > * 'loose-objects' : prune packed loose objects, then create a new pack from > a batch of loose objects. > * 'pack-files' : expire redundant packs from the multi-pack-index, then > repack using the multi-pack-index's incremental repack strategy. > * 'fetch' : fetch from each remote, storing the refs in 'refs/hidden//'. > > These tasks are all disabled by default, but can be enabled with config > options or run explicitly using "git maintenance run --task=". There are > additional config options to allow customizing the conditions for which the > tasks run during the '--auto' option. ('fetch' will never run with the > '--auto' option.) > > Because 'gc' is implemented as a maintenance task, the most dramatic change > of this series is to convert the 'git gc --auto' calls into 'git maintenance > run --auto' calls at the end of some Git commands. By default, the only > change is that 'git gc --auto' will be run below an additional 'git > maintenance' process. > > The 'git maintenance' builtin has a 'run' subcommand so it can be extended > later with subcommands that manage background maintenance, such as 'start', > 'stop', 'pause', or 'schedule'. These are not the subject of this series, as > it is important to focus on the maintenance activities themselves. > > An expert user could set up scheduled background maintenance themselves with > the current series. I have the following crontab data set up to run > maintenance on an hourly basis: > > 0 * * * * git -C /<path-to-repo> maintenance run --no-quiet >>/<path-to-repo>/.git/maintenance.log One thing I wonder about - now I have to go and make a new crontab (which is easy) or Task Scheduler task (which is a pain) for every repo, right? Is it infeasible to ask for 'git maintenance' to learn something like '--on /<path-to-repo> --on /<path-to-second-repo>'? Or better yet, some config like "maintenance.targetRepo = /<path-to-repo>"? > > My config includes all tasks except the 'gc' task. The hourly run is > over-aggressive, but is sufficient for testing. I'll replace it with daily > when I feel satisfied. > > Hopefully this direction is seen as a positive one. My goal was to add more > options for expert users, along with the flexibility to create background > maintenance via the OS in a later series. > > OUTLINE > ======= > > Patches 1-4 remove some references to the_repository in builtin/gc.c before > we start depending on code in that builtin. > > Patches 5-7 create the 'git maintenance run' builtin and subcommand as a > simple shim over 'git gc' and replaces calls to 'git gc --auto' from other > commands. For me, I'd prefer to see 'git maintenance run' get bigger and 'git gc --auto' get smaller or disappear. Is there a plan towards that direction, or is that out of scope for 'git maintenance run'? Similar examples I can think of include 'git annotate' and 'git pickaxe'. > > Patches 8-15 create new maintenance tasks. These are the same tasks sent in > the previous RFC. > > Patches 16-21 create more customization through config and perform other > polish items. > > FUTURE WORK > =========== > > * Add 'start', 'stop', and 'schedule' subcommands to initialize the > commands run in the background. > > > * Split the 'gc' builtin into smaller maintenance tasks that are enabled by > default, but might have different '--auto' conditions and more config > options. Like I mentioned above, for me, I'd rather just see the 'gc' builtin go away :) > > > * Replace config like 'gc.writeCommitGraph' and 'fetch.writeCommitGraph' > with use of the 'commit-graph' task. > > > > Thanks, -Stolee > > Derrick Stolee (21): > gc: use the_repository less often > gc: use repository in too_many_loose_objects() > gc: use repo config > gc: drop the_repository in log location > maintenance: create basic maintenance runner > maintenance: add --quiet option > maintenance: replace run_auto_gc() > maintenance: initialize task array and hashmap > maintenance: add commit-graph task > maintenance: add --task option > maintenance: take a lock on the objects directory > maintenance: add fetch task > maintenance: add loose-objects task > maintenance: add pack-files task > maintenance: auto-size pack-files batch > maintenance: create maintenance.<task>.enabled config > maintenance: use pointers to check --auto > maintenance: add auto condition for commit-graph task > maintenance: create auto condition for loose-objects > maintenance: add pack-files auto condition > midx: use start_delayed_progress() > > .gitignore | 1 + > Documentation/config.txt | 2 + > Documentation/config/maintenance.txt | 32 + > Documentation/fetch-options.txt | 5 +- > Documentation/git-clone.txt | 7 +- > Documentation/git-maintenance.txt | 124 ++++ > builtin.h | 1 + > builtin/am.c | 2 +- > builtin/commit.c | 2 +- > builtin/fetch.c | 6 +- > builtin/gc.c | 881 +++++++++++++++++++++++++-- > builtin/merge.c | 2 +- > builtin/rebase.c | 4 +- > commit-graph.c | 8 +- > commit-graph.h | 1 + > config.c | 24 +- > config.h | 2 + > git.c | 1 + > midx.c | 12 +- > midx.h | 1 + > object.h | 1 + > run-command.c | 7 +- > run-command.h | 2 +- > t/t5319-multi-pack-index.sh | 14 +- > t/t5510-fetch.sh | 2 +- > t/t5514-fetch-multiple.sh | 2 +- > t/t7900-maintenance.sh | 211 +++++++ > 27 files changed, 1265 insertions(+), 92 deletions(-) > create mode 100644 Documentation/config/maintenance.txt > create mode 100644 Documentation/git-maintenance.txt > create mode 100755 t/t7900-maintenance.sh > > > base-commit: 4a0fcf9f760c9774be77f51e1e88a7499b53d2e2 > Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-671%2Fderrickstolee%2Fmaintenance%2Fgc-v1 > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-671/derrickstolee/maintenance/gc-v1 > Pull-Request: https://github.com/gitgitgadget/git/pull/671 > -- > gitgitgadget
