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resolve major search perf regression in v3.2.0 (add redis cache to gi…
…t commit OID resolution) (#3685) * refactor OID resolution logic (review with whitespace off) * add oid resolution cache * add observability * CHANGELOG: update * custom cache implementation * enterprise/dev/Procfile: fix bug where zoekt is not listening * remove redundant return stmt * resolveCommitIODUncached * faster test * Update CHANGELOG.md
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123 changes: 123 additions & 0 deletions
123
cmd/frontend/graphqlbackend/git_commit_resolution_cache.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,123 @@ | ||
| package graphqlbackend | ||
|
|
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| import ( | ||
| "sync" | ||
| "time" | ||
|
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| "github.com/prometheus/client_golang/prometheus" | ||
| ) | ||
|
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| type resolutionCacheEntry struct { | ||
| t time.Time | ||
| value string | ||
| } | ||
|
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| type resolutionCache struct { | ||
| // ttl indicates how long before cache entries expire. There is no limit on | ||
| // the size of the cache except the effective # of repositories on the | ||
| // Sourcegraph instance. | ||
| ttl time.Duration | ||
|
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| // cacheEntries, if non-nil, is used to record the number of entries in the cache. | ||
| cacheEntries prometheus.Histogram | ||
|
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| // workerInterval, if non-zero, specifies the interval at which the worker | ||
| // checks for entries to evict. Defaults ttl / 2. | ||
| workerInterval time.Duration | ||
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| // mockSleep, if non-nil can be used to mock time.Sleep for testing purposes. | ||
| mockSleep func(d time.Duration) | ||
|
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| m sync.Map | ||
| } | ||
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| func (r *resolutionCache) Set(k, v string) { | ||
| r.m.Store(k, resolutionCacheEntry{ | ||
| t: time.Now(), | ||
| value: v, | ||
| }) | ||
| } | ||
|
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| func (r *resolutionCache) Get(k string) (string, bool) { | ||
| v, ok := r.m.Load(k) | ||
| if !ok { | ||
| return "", false | ||
| } | ||
| e := v.(resolutionCacheEntry) | ||
| if time.Since(e.t) >= r.ttl { | ||
| // entry has expired | ||
| r.m.Delete(k) | ||
| return "", false | ||
| } | ||
| return e.value, true | ||
| } | ||
|
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| func (r *resolutionCache) startWorker() *resolutionCache { | ||
| if r.workerInterval == 0 { | ||
| r.workerInterval = r.ttl / 2 | ||
| } | ||
| sleep := time.Sleep | ||
| if r.mockSleep != nil { | ||
| sleep = r.mockSleep | ||
| } | ||
| go func() { | ||
| for { | ||
| sleep(r.workerInterval) | ||
| size := 0 | ||
| r.m.Range(func(key, value interface{}) bool { | ||
| size++ | ||
| e := value.(resolutionCacheEntry) | ||
| if time.Since(e.t) >= r.ttl { | ||
| // entry has expired | ||
| r.m.Delete(key) | ||
| } | ||
| return true | ||
| }) | ||
| r.cacheEntries.Observe(float64(size)) | ||
| } | ||
| }() | ||
| return r | ||
| } | ||
|
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| var ( | ||
| // oidResolutionCache is used to cache Git commit OID resolution. This is | ||
| // used because OID resolution happens extremely often (e.g. multiple times | ||
| // per search result). | ||
| oidResolutionCache = (&resolutionCache{ | ||
| ttl: 60 * time.Second, | ||
| cacheEntries: prometheus.NewHistogram(prometheus.HistogramOpts{ | ||
| Namespace: "src", | ||
| Subsystem: "graphql", | ||
| Name: "git_commit_oid_resolution_cache_entries", | ||
| Help: "Total number of entries in the in-memory Git commit OID resolution cache.", | ||
| }), | ||
| }).startWorker() | ||
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| oidResolutionCounter = prometheus.NewCounterVec(prometheus.CounterOpts{ | ||
| Namespace: "src", | ||
| Subsystem: "graphql", | ||
| Name: "git_commit_oid_resolution_cache_hit", | ||
| Help: "Counts cache hits and misses for Git commit OID resolution.", | ||
| }, []string{"type"}) | ||
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| oidResolutionDuration = prometheus.NewHistogram(prometheus.HistogramOpts{ | ||
| Namespace: "src", | ||
| Subsystem: "graphql", | ||
| Name: "git_commit_oid_resolution_duration_seconds", | ||
| Help: "Total time spent performing uncached Git commit OID resolution.", | ||
| }) | ||
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| oidResolutionCacheLookupDuration = prometheus.NewHistogram(prometheus.HistogramOpts{ | ||
| Namespace: "src", | ||
| Subsystem: "graphql", | ||
| Name: "git_commit_oid_resolution_cache_lookup_duration_seconds", | ||
| Help: "Total time spent performing cache lookups for Git commit OID resolution.", | ||
| }) | ||
| ) | ||
|
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| func init() { | ||
| prometheus.MustRegister(oidResolutionCache.cacheEntries) | ||
| prometheus.MustRegister(oidResolutionCounter) | ||
| prometheus.MustRegister(oidResolutionDuration) | ||
| prometheus.MustRegister(oidResolutionCacheLookupDuration) | ||
| } |
96 changes: 96 additions & 0 deletions
96
cmd/frontend/graphqlbackend/git_commit_resolution_cache_test.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,96 @@ | ||
| package graphqlbackend | ||
|
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| import ( | ||
| "fmt" | ||
| "testing" | ||
| "time" | ||
|
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| "github.com/prometheus/client_golang/prometheus" | ||
| ) | ||
|
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| func TestGitCommitResolutionCache(t *testing.T) { | ||
| doneSleep := make(chan struct{}) | ||
| cache := (&resolutionCache{ | ||
| ttl: 15 * time.Millisecond, | ||
| cacheEntries: prometheus.NewHistogram(prometheus.HistogramOpts{ | ||
| Namespace: "src", | ||
| Subsystem: "graphql", | ||
| Name: "git_commit_oid_resolution_cache_entries", | ||
| Help: "Total number of entries in the in-memory Git commit OID resolution cache.", | ||
| }), | ||
| mockSleep: func(d time.Duration) { | ||
| <-doneSleep | ||
| }, | ||
| }).startWorker() | ||
|
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| cache.Set("repo-1", "commit-1") | ||
| cache.Set("repo-2", "commit-2") | ||
| if v, ok := cache.Get("repo-1"); !ok || v != "commit-1" { | ||
| t.Fatal("expected cache get to succeed") | ||
| } | ||
| if v, ok := cache.Get("repo-2"); !ok || v != "commit-2" { | ||
| t.Fatal("expected cache get to succeed") | ||
| } | ||
| doneSleep <- struct{}{} // cause worker to begin a single iteration | ||
| time.Sleep(30 * time.Millisecond) // wait long enough for TTL | ||
| if _, ok := cache.Get("repo-1"); ok { | ||
| t.Fatal("expected cache entry to have expired") | ||
| } | ||
| if _, ok := cache.Get("repo-2"); ok { | ||
| t.Fatal("expected cache entry to have expired") | ||
| } | ||
| } | ||
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| // Merely shows that the cache can support a very high concurrent read rate | ||
| // with a low write rate. Run it like: | ||
| // | ||
| // $ go test -bench BenchmarkGitCommitResolutionCache -benchtime=30s ./cmd/frontend/graphqlbackend/ | ||
| // BenchmarkGitCommitResolutionCache/8-8 200000000 202 ns/op | ||
| // BenchmarkGitCommitResolutionCache/16-8 100000000 410 ns/op | ||
| // BenchmarkGitCommitResolutionCache/32-8 50000000 879 ns/op | ||
| // BenchmarkGitCommitResolutionCache/64-8 30000000 1709 ns/op | ||
| // BenchmarkGitCommitResolutionCache/128-8 20000000 3345 ns/op | ||
| // BenchmarkGitCommitResolutionCache/256-8 20000000 6177 ns/op | ||
| // | ||
| // The last one shows that while 256 concurrent cache reads are occurring we | ||
| // can perform 8 cache reads in 6177ns. | ||
| func BenchmarkGitCommitResolutionCache(b *testing.B) { | ||
| cache := (&resolutionCache{ | ||
| ttl: 10 * time.Minute, | ||
| cacheEntries: prometheus.NewHistogram(prometheus.HistogramOpts{ | ||
| Namespace: "src", | ||
| Subsystem: "graphql", | ||
| Name: "git_commit_oid_resolution_cache_entries", | ||
| Help: "Total number of entries in the in-memory Git commit OID resolution cache.", | ||
| }), | ||
| }).startWorker() | ||
|
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| cache.Set("repo-1", "commit-1") | ||
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| for _, concurrentReads := range []int{8, 16, 32, 64, 128, 256} { | ||
| b.Run(fmt.Sprint(concurrentReads), func(b *testing.B) { | ||
| done := make(chan bool) | ||
| defer close(done) | ||
| for i := 0; i < concurrentReads; i++ { | ||
| go func() { | ||
| for { | ||
| select { | ||
| case <-done: | ||
| return | ||
| default: | ||
| cache.Get("repo-1") | ||
| } | ||
| } | ||
| }() | ||
| } | ||
| time.Sleep(1 * time.Second) // Time for goroutines to start running. | ||
| b.ResetTimer() | ||
|
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| for n := 0; n < b.N; n++ { | ||
| if v, ok := cache.Get("repo-1"); !ok || v != "commit-1" { | ||
| b.Fatal("expected cache get to succeed") | ||
| } | ||
| } | ||
| }) | ||
| } | ||
| } |
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