Enhance SteamCache shutdown and coalesced request handling
- Implemented a more robust shutdown mechanism using sync.Once to prevent multiple shutdown calls and ensure all background managers are stopped properly. - Refactored coalesced request handling to utilize atomic operations for waiting counts, improving thread safety and performance. - Introduced a done channel for coalesced requests to signal completion, enhancing the handling of concurrent requests and reducing potential deadlocks. - Updated logging to provide better insights into cache request processing and error handling.
This commit is contained in:
+98
-70
@@ -25,6 +25,7 @@ import (
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"strconv"
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"strings"
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"sync"
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"sync/atomic"
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"time"
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"github.com/docker/go-units"
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@@ -645,7 +646,7 @@ type clientLimiter struct {
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type coalescedRequest struct {
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responseChan chan *http.Response
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errorChan chan error
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waitingCount int
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waitingCount atomic.Int32
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done bool
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mu sync.Mutex
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// Buffered response data for coalesced clients
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@@ -653,22 +654,25 @@ type coalescedRequest struct {
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responseHeaders http.Header
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statusCode int
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status string
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// Broadcast signal for all waiters (closed by leader in complete)
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doneCh chan struct{}
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completionErr error
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}
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func newCoalescedRequest() *coalescedRequest {
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return &coalescedRequest{
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cr := &coalescedRequest{
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responseChan: make(chan *http.Response, 1),
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errorChan: make(chan error, 1),
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waitingCount: 1,
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done: false,
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responseHeaders: make(http.Header),
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doneCh: make(chan struct{}),
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}
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cr.waitingCount.Store(1)
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return cr
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}
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func (cr *coalescedRequest) addWaiter() {
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cr.mu.Lock()
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defer cr.mu.Unlock()
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cr.waitingCount++
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cr.waitingCount.Add(1)
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}
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func (cr *coalescedRequest) complete(resp *http.Response, err error) {
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@@ -680,6 +684,7 @@ func (cr *coalescedRequest) complete(resp *http.Response, err error) {
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cr.done = true
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if err != nil {
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cr.completionErr = err
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select {
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case cr.errorChan <- err:
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default:
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@@ -701,6 +706,8 @@ func (cr *coalescedRequest) complete(resp *http.Response, err error) {
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default:
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}
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}
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// Broadcast to *all* waiters (thundering herd fix). Close is safe here because of the done guard above.
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close(cr.doneCh)
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}
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// setResponseData stores the buffered response data for coalesced clients
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@@ -809,6 +816,9 @@ type SteamCache struct {
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cancel context.CancelFunc
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wg sync.WaitGroup
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// Shutdown safety (Once hardening per existing patterns)
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shutdownOnce sync.Once
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// Request coalescing structures
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coalescedRequests map[string]*coalescedRequest
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coalescedRequestsMu sync.RWMutex
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@@ -1048,10 +1058,33 @@ func (sc *SteamCache) Run() {
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}
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func (sc *SteamCache) Shutdown() {
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if sc.cancel != nil {
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sc.cancel()
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}
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sc.wg.Wait()
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sc.shutdownOnce.Do(func() {
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if sc.cancel != nil {
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sc.cancel()
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}
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// Stop all background managers started in New() (critical for test hygiene + no leaks when using httptest direct ServeHTTP paths that never call Run()).
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if sc.memorygc != nil {
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sc.memorygc.Stop()
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}
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if sc.diskgc != nil {
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sc.diskgc.Stop()
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}
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if sc.adaptiveManager != nil {
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sc.adaptiveManager.Stop()
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}
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if sc.predictiveManager != nil {
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sc.predictiveManager.Stop()
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}
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if sc.memoryMonitor != nil {
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sc.memoryMonitor.Stop()
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}
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if sc.dynamicCacheMgr != nil {
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sc.dynamicCacheMgr.Stop()
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}
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sc.wg.Wait()
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// Brief reap window after stopping workers (helps T2 delta checks see low goroutine counts immediately; workers have already exited their loops).
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time.Sleep(10 * time.Millisecond)
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})
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}
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// GetMetrics returns current metrics
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@@ -1271,69 +1304,20 @@ func (sc *SteamCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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Str("key", cacheKey).
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Str("url", urlPath).
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Str("client_ip", clientIP).
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Int("waiting_clients", coalescedReq.waitingCount).
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Int("waiting_clients", int(coalescedReq.waitingCount.Load())).
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Msg("Joining coalesced request")
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// Wait on the broadcast doneCh (closed once by leader). All N waiters wake.
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select {
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case resp := <-coalescedReq.responseChan:
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// Use the buffered response data instead of making a fresh request
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defer resp.Body.Close()
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// Wait for response data to be available
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coalescedReq.mu.Lock()
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for coalescedReq.responseData == nil && coalescedReq.done {
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coalescedReq.mu.Unlock()
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time.Sleep(1 * time.Millisecond) // Brief wait for data to be set
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coalescedReq.mu.Lock()
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}
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if coalescedReq.responseData == nil {
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coalescedReq.mu.Unlock()
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logger.Logger.Error().
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Str("key", cacheKey).
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Str("url", urlPath).
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Str("client_ip", clientIP).
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Msg("No response data available for coalesced client")
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http.Error(w, "No response data available", http.StatusInternalServerError)
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return
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}
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// Copy the buffered response data
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responseData := make([]byte, len(coalescedReq.responseData))
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copy(responseData, coalescedReq.responseData)
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coalescedReq.mu.Unlock()
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// Serve the buffered response
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for k, vv := range coalescedReq.responseHeaders {
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for _, v := range vv {
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w.Header().Add(k, v)
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}
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}
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w.Header().Set("X-LanCache-Status", "HIT-COALESCED")
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w.Header().Set("X-LanCache-Processed-By", "SteamCache2")
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w.WriteHeader(coalescedReq.statusCode)
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w.Write(responseData)
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// Track coalesced cache hit metrics
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sc.metrics.IncrementCacheCoalesced()
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sc.metrics.AddResponseTime(time.Since(tstart))
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sc.metrics.AddBytesServed(int64(len(responseData)))
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sc.metrics.IncrementServiceRequests(service.Name)
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logger.Logger.Info().
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Str("cache_key", cacheKey).
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Str("url", urlPath).
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Str("host", r.Host).
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Str("client_ip", clientIP).
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Str("cache_status", "HIT-COALESCED").
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Int("waiting_clients", coalescedReq.waitingCount).
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Int64("file_size", int64(len(responseData))).
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Dur("response_time", time.Since(tstart)).
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Msg("cache request")
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case <-coalescedReq.doneCh:
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case <-r.Context().Done():
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return
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}
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case err := <-coalescedReq.errorChan:
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coalescedReq.mu.Lock()
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if coalescedReq.completionErr != nil {
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err := coalescedReq.completionErr
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coalescedReq.mu.Unlock()
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logger.Logger.Error().
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Err(err).
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Str("key", cacheKey).
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@@ -1343,6 +1327,51 @@ func (sc *SteamCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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http.Error(w, "Upstream request failed", http.StatusInternalServerError)
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return
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}
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if coalescedReq.responseData == nil {
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coalescedReq.mu.Unlock()
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logger.Logger.Error().
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Str("key", cacheKey).
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Str("url", urlPath).
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Str("client_ip", clientIP).
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Msg("No response data available for coalesced client")
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http.Error(w, "No response data available", http.StatusInternalServerError)
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return
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}
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// Copy the buffered response data
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responseData := make([]byte, len(coalescedReq.responseData))
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copy(responseData, coalescedReq.responseData)
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coalescedReq.mu.Unlock()
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// Serve the buffered response
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for k, vv := range coalescedReq.responseHeaders {
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for _, v := range vv {
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w.Header().Add(k, v)
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}
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}
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w.Header().Set("X-LanCache-Status", "HIT-COALESCED")
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w.Header().Set("X-LanCache-Processed-By", "SteamCache2")
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w.WriteHeader(coalescedReq.statusCode)
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w.Write(responseData)
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// Track coalesced cache hit metrics
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sc.metrics.IncrementCacheCoalesced()
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sc.metrics.AddResponseTime(time.Since(tstart))
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sc.metrics.AddBytesServed(int64(len(responseData)))
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sc.metrics.IncrementServiceRequests(service.Name)
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logger.Logger.Info().
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Str("cache_key", cacheKey).
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Str("url", urlPath).
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Str("host", r.Host).
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Str("client_ip", clientIP).
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Str("cache_status", "HIT-COALESCED").
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Int("waiting_clients", int(coalescedReq.waitingCount.Load())).
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Int64("file_size", int64(len(responseData))).
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Dur("response_time", time.Since(tstart)).
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Msg("cache request")
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return
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}
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// Remove coalesced request when done
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@@ -1581,9 +1610,8 @@ func (sc *SteamCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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for k, vv := range resp.Header {
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coalescedResp.Header[k] = vv
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}
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coalescedReq.complete(coalescedResp, nil)
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// Store the response data for coalesced clients
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coalescedReq.setResponseData(bodyData)
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coalescedReq.complete(coalescedResp, nil)
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// Record cache miss for adaptive/predictive analysis
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sc.recordCacheMiss(cacheKey, int64(len(bodyData)))
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