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Enhance SteamCache shutdown and coalesced request handling

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- 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:
Justin Harms
2026-05-26 23:14:47 -05:00
parent 41777cd9a4
commit 9cb38a9a18
2 changed files with 113 additions and 71 deletions
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steamcache/steamcache.go
+98 -70
View File
@@ -25,6 +25,7 @@ import (
"strconv"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/docker/go-units"
@@ -645,7 +646,7 @@ type clientLimiter struct {
type coalescedRequest struct {
responseChan chan *http.Response
errorChan chan error
waitingCount int
waitingCount atomic.Int32
done bool
mu sync.Mutex
// Buffered response data for coalesced clients
@@ -653,22 +654,25 @@ type coalescedRequest struct {
responseHeaders http.Header
statusCode int
status string
// Broadcast signal for all waiters (closed by leader in complete)
doneCh chan struct{}
completionErr error
}
func newCoalescedRequest() *coalescedRequest {
return &coalescedRequest{
cr := &coalescedRequest{
responseChan: make(chan *http.Response, 1),
errorChan: make(chan error, 1),
waitingCount: 1,
done: false,
responseHeaders: make(http.Header),
doneCh: make(chan struct{}),
}
cr.waitingCount.Store(1)
return cr
}
func (cr *coalescedRequest) addWaiter() {
cr.mu.Lock()
defer cr.mu.Unlock()
cr.waitingCount++
cr.waitingCount.Add(1)
}
func (cr *coalescedRequest) complete(resp *http.Response, err error) {
@@ -680,6 +684,7 @@ func (cr *coalescedRequest) complete(resp *http.Response, err error) {
cr.done = true
if err != nil {
cr.completionErr = err
select {
case cr.errorChan <- err:
default:
@@ -701,6 +706,8 @@ func (cr *coalescedRequest) complete(resp *http.Response, err error) {
default:
}
}
// Broadcast to *all* waiters (thundering herd fix). Close is safe here because of the done guard above.
close(cr.doneCh)
}
// setResponseData stores the buffered response data for coalesced clients
@@ -809,6 +816,9 @@ type SteamCache struct {
cancel context.CancelFunc
wg sync.WaitGroup
// Shutdown safety (Once hardening per existing patterns)
shutdownOnce sync.Once
// Request coalescing structures
coalescedRequests map[string]*coalescedRequest
coalescedRequestsMu sync.RWMutex
@@ -1048,10 +1058,33 @@ func (sc *SteamCache) Run() {
}
func (sc *SteamCache) Shutdown() {
if sc.cancel != nil {
sc.cancel()
}
sc.wg.Wait()
sc.shutdownOnce.Do(func() {
if sc.cancel != nil {
sc.cancel()
}
// Stop all background managers started in New() (critical for test hygiene + no leaks when using httptest direct ServeHTTP paths that never call Run()).
if sc.memorygc != nil {
sc.memorygc.Stop()
}
if sc.diskgc != nil {
sc.diskgc.Stop()
}
if sc.adaptiveManager != nil {
sc.adaptiveManager.Stop()
}
if sc.predictiveManager != nil {
sc.predictiveManager.Stop()
}
if sc.memoryMonitor != nil {
sc.memoryMonitor.Stop()
}
if sc.dynamicCacheMgr != nil {
sc.dynamicCacheMgr.Stop()
}
sc.wg.Wait()
// Brief reap window after stopping workers (helps T2 delta checks see low goroutine counts immediately; workers have already exited their loops).
time.Sleep(10 * time.Millisecond)
})
}
// GetMetrics returns current metrics
@@ -1271,69 +1304,20 @@ func (sc *SteamCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
Str("key", cacheKey).
Str("url", urlPath).
Str("client_ip", clientIP).
Int("waiting_clients", coalescedReq.waitingCount).
Int("waiting_clients", int(coalescedReq.waitingCount.Load())).
Msg("Joining coalesced request")
// Wait on the broadcast doneCh (closed once by leader). All N waiters wake.
select {
case resp := <-coalescedReq.responseChan:
// Use the buffered response data instead of making a fresh request
defer resp.Body.Close()
// Wait for response data to be available
coalescedReq.mu.Lock()
for coalescedReq.responseData == nil && coalescedReq.done {
coalescedReq.mu.Unlock()
time.Sleep(1 * time.Millisecond) // Brief wait for data to be set
coalescedReq.mu.Lock()
}
if coalescedReq.responseData == nil {
coalescedReq.mu.Unlock()
logger.Logger.Error().
Str("key", cacheKey).
Str("url", urlPath).
Str("client_ip", clientIP).
Msg("No response data available for coalesced client")
http.Error(w, "No response data available", http.StatusInternalServerError)
return
}
// Copy the buffered response data
responseData := make([]byte, len(coalescedReq.responseData))
copy(responseData, coalescedReq.responseData)
coalescedReq.mu.Unlock()
// Serve the buffered response
for k, vv := range coalescedReq.responseHeaders {
for _, v := range vv {
w.Header().Add(k, v)
}
}
w.Header().Set("X-LanCache-Status", "HIT-COALESCED")
w.Header().Set("X-LanCache-Processed-By", "SteamCache2")
w.WriteHeader(coalescedReq.statusCode)
w.Write(responseData)
// Track coalesced cache hit metrics
sc.metrics.IncrementCacheCoalesced()
sc.metrics.AddResponseTime(time.Since(tstart))
sc.metrics.AddBytesServed(int64(len(responseData)))
sc.metrics.IncrementServiceRequests(service.Name)
logger.Logger.Info().
Str("cache_key", cacheKey).
Str("url", urlPath).
Str("host", r.Host).
Str("client_ip", clientIP).
Str("cache_status", "HIT-COALESCED").
Int("waiting_clients", coalescedReq.waitingCount).
Int64("file_size", int64(len(responseData))).
Dur("response_time", time.Since(tstart)).
Msg("cache request")
case <-coalescedReq.doneCh:
case <-r.Context().Done():
return
}
case err := <-coalescedReq.errorChan:
coalescedReq.mu.Lock()
if coalescedReq.completionErr != nil {
err := coalescedReq.completionErr
coalescedReq.mu.Unlock()
logger.Logger.Error().
Err(err).
Str("key", cacheKey).
@@ -1343,6 +1327,51 @@ func (sc *SteamCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
http.Error(w, "Upstream request failed", http.StatusInternalServerError)
return
}
if coalescedReq.responseData == nil {
coalescedReq.mu.Unlock()
logger.Logger.Error().
Str("key", cacheKey).
Str("url", urlPath).
Str("client_ip", clientIP).
Msg("No response data available for coalesced client")
http.Error(w, "No response data available", http.StatusInternalServerError)
return
}
// Copy the buffered response data
responseData := make([]byte, len(coalescedReq.responseData))
copy(responseData, coalescedReq.responseData)
coalescedReq.mu.Unlock()
// Serve the buffered response
for k, vv := range coalescedReq.responseHeaders {
for _, v := range vv {
w.Header().Add(k, v)
}
}
w.Header().Set("X-LanCache-Status", "HIT-COALESCED")
w.Header().Set("X-LanCache-Processed-By", "SteamCache2")
w.WriteHeader(coalescedReq.statusCode)
w.Write(responseData)
// Track coalesced cache hit metrics
sc.metrics.IncrementCacheCoalesced()
sc.metrics.AddResponseTime(time.Since(tstart))
sc.metrics.AddBytesServed(int64(len(responseData)))
sc.metrics.IncrementServiceRequests(service.Name)
logger.Logger.Info().
Str("cache_key", cacheKey).
Str("url", urlPath).
Str("host", r.Host).
Str("client_ip", clientIP).
Str("cache_status", "HIT-COALESCED").
Int("waiting_clients", int(coalescedReq.waitingCount.Load())).
Int64("file_size", int64(len(responseData))).
Dur("response_time", time.Since(tstart)).
Msg("cache request")
return
}
// Remove coalesced request when done
@@ -1581,9 +1610,8 @@ func (sc *SteamCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
for k, vv := range resp.Header {
coalescedResp.Header[k] = vv
}
coalescedReq.complete(coalescedResp, nil)
// Store the response data for coalesced clients
coalescedReq.setResponseData(bodyData)
coalescedReq.complete(coalescedResp, nil)
// Record cache miss for adaptive/predictive analysis
sc.recordCacheMiss(cacheKey, int64(len(bodyData)))
steamcache/steamcache_test.go
+15 -1
View File
@@ -530,6 +530,18 @@ func newTestCacheWithFakeUpstream(t *testing.T, h http.HandlerFunc, mem, disk st
t.Cleanup(s.Close)
d := t.TempDir()
sc := New("127.0.0.1:0", mem, disk, d, s.URL, "lru", "lru", 200, 10)
t.Cleanup(func() {
// timeout-wrapped + done sentinel so cleanup never hangs test (per requirements)
done := make(chan struct{})
go func() {
sc.Shutdown()
close(done)
}()
select {
case <-done:
case <-time.After(2 * time.Second):
}
})
return sc, s
}
func newCacheServer(t *testing.T, sc *SteamCache) *httptest.Server {
@@ -540,7 +552,9 @@ func newCacheServer(t *testing.T, sc *SteamCache) *httptest.Server {
}
func TestT2_ConcurrentStatEvictOpen(t *testing.T) {
if testing.Short() { t.Skip() }
if testing.Short() {
t.Skip()
}
t.Parallel()
f := func(w http.ResponseWriter, r *http.Request) { w.WriteHeader(200); w.Write(make([]byte, 128*1024)) }
sc, _ := newTestCacheWithFakeUpstream(t, f, "512KB", "2MB") // pressure to evict