feat: add size-based cache eviction (#1170)

The cache server retired entries 30 days after creation regardless of use, so a job that ran often enough to keep its cache warm still lost it on a fixed schedule. Nothing bounded the disk either.

Retention now counts from last access alone, and a repository over its limit sheds least recently accessed entries until it fits, enforced on commit as well as on the periodic sweep.

```yaml
cache:
  retention: 168h        # remove entries not accessed for seven days
  repo_size_limit: 10GB  # cap each repository
  size_limit: 0          # cap the whole cache, off by default
  sweep_interval: 1h     # minimum time between sweeps
```

Sizes accept `10GB`, `512mb`, `1TiB` or a plain byte count, binary either way. Leave a key out for its default; `0` turns a limit off, and `0s` does the same for `retention`. Whatever these allow, the cache also sheds entries to keep free space above `health_check.min_free_disk_space_mb` when health checks are enabled, so it cannot grow past the point where the runner stops accepting work.

Supporting fixes: serving an entry stamps its access time, so a find cannot hand a job a download URL for an entry the next eviction is about to remove; an entry larger than the limit is dropped on its own account rather than emptying its repository to make room; and a blob that cannot be unlinked keeps its row, so the next sweep retries instead of orphaning bytes no limit can account for.

Closes https://gitea.com/gitea/runner/issues/1168

---------

Co-authored-by: silverwind <me@silverwind.io>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1170
Reviewed-by: silverwind <2021+silverwind@noreply.gitea.com>
This commit is contained in:
bircni
2026-08-18 15:32:53 +00:00
parent 6c6a878403
commit be90c01468
21 changed files with 750 additions and 170 deletions
+6
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@@ -273,6 +273,12 @@ A password in a proxy URL is hidden in job logs. Any step can still read it, bec
Each runner starts its own cache server automatically. Cache entries are local to that runner — runners do not share a cache by default.
**Eviction**
An entry nothing has read or written for `retention` is removed, and a repository past `repo_size_limit` loses its least recently accessed entries until it fits; `size_limit` caps the whole cache the same way. Age alone never retires an entry still in use, and whatever these allow, the cache keeps free space above `health_check.min_free_disk_space_mb` when health checks are enabled.
These apply where the cache server runs, so on a shared server they belong in *its* config, not the runners'. See `retention`, `repo_size_limit`, `size_limit` and `sweep_interval` in [config.example.yaml](internal/pkg/config/config.example.yaml) for units and defaults.
**Cache service v2**
`actions/cache@v4.2` and later can use the *cache service v2* API. The runner serves it from the same store as v1, on by default, and it works with `external_server`. Turn it off with: