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gitserver(fs): Remove caching of cloned state (#63066)

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I thought it might be nice to save on a few IOPS from the Stat calls to check if a repo is cloned by caching it for a bit. But turns out that the mutex locking and unlocking is more expensive than the stat operation.

We can come back here later and see if we can optimize it, we never had this in the past so this will be no regression.

Some background on mutex performance: https://stackoverflow.com/questions/57562606/why-does-sync-mutex-largely-drop-performance-when-goroutine-contention-is-more-t

Closes SRC-322

Test plan:

Without the cache, the tests still pass.
This commit is contained in:
Erik Seliger 2024-06-04 22:54:11 +02:00 committed by GitHub
parent bf851d4598
commit 54472b70a0
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1 changed files with 5 additions and 46 deletions
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51
cmd/gitserver/internal/gitserverfs/fs.go
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@ -6,7 +6,6 @@ import (
"path/filepath"
"strings"
"sync"
"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/sourcegraph/log"
@ -42,11 +41,9 @@ type FS interface {
func New(observationCtx *observation.Context, reposDir string) FS {
return &realGitserverFS{
logger: observationCtx.Logger.Scoped("gitserverfs"),
observationCtx: observationCtx,
reposDir: reposDir,
clonedState: make(map[api.RepoName]struct{}),
lastCloneStateReset: time.Now(),
logger: observationCtx.Logger.Scoped("gitserverfs"),
observationCtx: observationCtx,
reposDir: reposDir,
}
}
@ -54,10 +51,6 @@ type realGitserverFS struct {
reposDir string
observationCtx *observation.Context
logger log.Logger
// clonedState keeps track of the clone state of a repo.
clonedState map[api.RepoName]struct{}
cloneStateMu sync.Mutex
lastCloneStateReset time.Time
}
func (r *realGitserverFS) Initialize() error {
@ -107,46 +100,12 @@ func (r *realGitserverFS) VisitRepos(visit func(api.RepoName, common.GitDir) (do
return nil
}
const cloneStateResetInterval = 5 * time.Minute
func (r *realGitserverFS) RepoCloned(name api.RepoName) (bool, error) {
r.cloneStateMu.Lock()
defer r.cloneStateMu.Unlock()
// Every few minutes, we invalidate the entire cache, in case we fall into
// some bad state, this'll fix the state every now and then.
if time.Since(r.lastCloneStateReset) > cloneStateResetInterval {
r.clonedState = make(map[api.RepoName]struct{})
}
_, cloned := r.clonedState[name]
if cloned {
return true, nil
}
cloned, err := repoCloned(r.RepoDir(name))
if err != nil {
return false, err
}
if cloned {
r.clonedState[name] = struct{}{}
}
return cloned, nil
return repoCloned(r.RepoDir(name))
}
func (r *realGitserverFS) RemoveRepo(name api.RepoName) error {
err := removeRepoDirectory(r.logger, r.reposDir, r.RepoDir(name))
// Mark as not cloned anymore in cache. We even remove it from the cache
// when the deletion failed partially, in the next call we'll recheck if
// the repo is still there.
r.cloneStateMu.Lock()
delete(r.clonedState, name)
r.cloneStateMu.Unlock()
return err
return removeRepoDirectory(r.logger, r.reposDir, r.RepoDir(name))
}
// iterateGitDirs walks over the reposDir on disk and calls walkFn for each of the