Add receiver downscale endpoint #88
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yuchen-db
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christopherzli,
jnyi,
hczhu-db and
yulong-db
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pkg/server/http/http.go
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| @@ -17,6 +15,11 @@ import ( | |||
| toolkit_web "github.com/prometheus/exporter-toolkit/web" | |||
| "golang.org/x/net/http2" | |||
| "golang.org/x/net/http2/h2c" | |||
| "net/http" | |||
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please fix the import convention for go: https://google.github.io/styleguide/go/best-practices.html#import-ordering
cmd/thanos/receive.go
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| @@ -311,6 +311,8 @@ func runReceive( | |||
| httpserver.WithGracePeriod(time.Duration(*conf.httpGracePeriod)), | |||
| httpserver.WithTLSConfig(*conf.httpTLSConfig), | |||
| ) | |||
| var lastDownscalePrepareTimestamp *int64 = nil | |||
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this implementation assumes the pod won't restart, to preserve the state, we might need to persist it on local PVC too, any thoughts?
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yes but it's safe to lose this state. rollout operator will only do downscale if the returned timestamp is more than 30 seconds ago. If we lose this state, it returns the current timestamp and downscale will not accidentally happen. In the worst case, a scheduled downscale will be delayed for 30 seconds.
pkg/receive/multitsdb.go
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| @@ -106,6 +106,14 @@ func (t *MultiTSDB) SkipMatchExternalLabels() { | |||
| t.skipMatchExternalLabels = true | |||
| } | |||
|
|
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| func (t *MultiTSDB) GetTenants() map[string]*tenant { | |||
| return t.tenants | |||
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This map is protected by mtx. A call site of GetTenants() can hold a pointer to the map and do reads/writes while the map is being updated by other goroutines. That'd be a data race.
It's safer to return a deep copy of the map if copying is not too expensive.
pkg/server/http/http.go
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| func RegisterDownscale[K comparable, V any](s *Server, m map[K]V, mtx *sync.RWMutex, t *int64) { | ||
| s.mux.Handle("/-/downscale", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { | ||
| mtx.RLock() | ||
| n := len(m) |
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Don't pass in a map, if only the size of map is needed. Pass in the size of the map.
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the size of the map changes dynamically during handler runtime and Golang passes map by reference
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The endpoint expose number of TSDBs, rollout operator will patch the sts if n_tsdb=0
related PRs:
https://github.com/databricks/universe/pull/753653
databricks/rollout-operator#7