cache: Per-client fair-share bandwidth on table uplink

steamcache/steamcache.go

@@ -55,6 +55,9 @@ type SteamCache struct {
 	clientRateLimiter    *clientRateLimiter
 	maxRequestsPerClient int64
 
+	// Per-client uplink bandwidth shaping (see bandwidth.go); nil/disabled = unlimited
+	bandwidth *clientBandwidthLimiter
+
 	// Hardening config fields (plumbed)
 	maxObjectSize  int64
 	trustedProxies []string
@@ -85,7 +88,7 @@ const DefaultNegativeTTL = 5 * time.Minute
 // negativeTTL is a Go duration string for 404/410 negative cache entries; empty means 5m.
 // Callers must check the returned error.
 // Prefer NewWithOptions (or config file) for forward compatibility. See README migration notes.
-func New(address string, memorySize string, diskSize string, diskPath, upstream, memoryGC, diskGC string, maxConcurrentRequests int64, maxRequestsPerClient int64, maxObjectSize string, trustedProxies []string, negativeTTL string) (*SteamCache, error) {
+func New(address string, memorySize string, diskSize string, diskPath, upstream, memoryGC, diskGC string, maxConcurrentRequests int64, maxRequestsPerClient int64, maxObjectSize string, trustedProxies []string, negativeTTL string, uplinkBandwidth string, maxBytesPerClientPerSec int64) (*SteamCache, error) {
 	memorysize, err := units.FromHumanSize(memorySize)
 	if err != nil {
 		return nil, fmt.Errorf("invalid memory size: %w", err)
@@ -114,6 +117,17 @@ func New(address string, memorySize string, diskSize string, diskPath, upstream,
 		return nil, err
 	}
 
+	var uplinkBytes int64
+	if uplinkBandwidth != "" && uplinkBandwidth != "0" {
+		uplinkBytes, err = units.FromHumanSize(uplinkBandwidth)
+		if err != nil {
+			return nil, fmt.Errorf("invalid uplink bandwidth: %w", err)
+		}
+	}
+	if maxBytesPerClientPerSec < 0 {
+		return nil, fmt.Errorf("negative max_bytes_per_client_per_sec not allowed")
+	}
+
 	c := cache.New()
 
 	var m *memory.MemoryFS
@@ -178,6 +192,7 @@ func New(address string, memorySize string, diskSize string, diskPath, upstream,
 		requestSemaphore:      semaphore.NewWeighted(maxConcurrentRequests),
 		clientRateLimiter:     newClientRateLimiter(maxRequestsPerClient),
 		maxRequestsPerClient:  maxRequestsPerClient,
+		bandwidth:             newClientBandwidthLimiter(uplinkBytes, maxBytesPerClientPerSec),
 		shutdownCh:            make(chan struct{}),
 
 		// Hardening config plumbed