gitea/modules/repository
Peter Gardfjäll e28cc79c92
Improve sync performance for pull-mirrors (#19125)
This addresses https://github.com/go-gitea/gitea/issues/18352

It aims to improve performance (and resource use) of the `SyncReleasesWithTags` operation for pull-mirrors.

For large repositories with many tags, `SyncReleasesWithTags` can be a costly operation (taking several minutes to complete). The reason is two-fold:
    
1. on sync, every upstream repo tag is compared (for changes) against existing local entries in the release table to ensure that they are up-to-date.
    
2. the procedure for getting _each tag_ involves a series of git operations    
    ```bash
     git show-ref --tags -- v8.2.4477
     git cat-file -t 29ab6ce9f36660cffaad3c8789e71162e5db5d2f
     git cat-file -p 29ab6ce9f36660cffaad3c8789e71162e5db5d2f
     git rev-list --count 29ab6ce9f36660cffaad3c8789e71162e5db5d2f
     ```    

     of which the `git rev-list --count` can be particularly heavy.
    
This PR optimizes performance for pull-mirrors. We utilize the fact that a pull-mirror is always identical to its upstream and rebuild the entire release table on every sync and use a batch `git for-each-ref .. refs/tags` call to retrieve all tags in one go.
    
For large mirror repos, with hundreds of annotated tags, this brings down the duration of the sync operation from several minutes to a few seconds. A few unscientific examples run on my local machine:

- https://github.com/spring-projects/spring-boot (223 tags)
  - before: `0m28,673s`
  - after: `0m2,244s`
- https://github.com/kubernetes/kubernetes (890 tags)
  - before: `8m00s`
  - after: `0m8,520s`
- https://github.com/vim/vim (13954 tags)
  - before: `14m20,383s`
  - after: `0m35,467s`

 

I added a `foreachref` package which contains a flexible way of specifying which reference fields are of interest (`git-for-each-ref(1)`) and to produce a parser for the expected output. These could be reused in other places where `for-each-ref` is used.  I'll add unit tests for those if the overall PR looks promising.
2022-03-31 14:30:40 +02:00
..
commits_test.go Propagate context and ensure git commands run in request context (#17868) 2022-01-19 23:26:57 +00:00
commits.go Propagate context and ensure git commands run in request context (#17868) 2022-01-19 23:26:57 +00:00
create_test.go Move organization related structs into sub package (#18518) 2022-03-29 14:29:02 +08:00
create.go Move init repository related functions to modules (#19159) 2022-03-29 15:23:45 +08:00
generate.go Make git.OpenRepository accept Context (#19260) 2022-03-30 03:13:41 +08:00
hooks.go format with gofumpt (#18184) 2022-01-20 18:46:10 +01:00
init.go Make git.OpenRepository accept Context (#19260) 2022-03-30 03:13:41 +08:00
main_test.go Decouple unit test code from business code (#17623) 2021-11-12 22:36:47 +08:00
push.go Delete old git.NewCommand() and use it as git.NewCommandContext() (#18552) 2022-02-06 20:01:47 +01:00
repo.go Improve sync performance for pull-mirrors (#19125) 2022-03-31 14:30:40 +02:00