cmd/go-cache-plugin: make the --debug flag a bit vector

Author: creachadair

cmd/go-cache-plugin/commands.go

@@ -33,9 +33,15 @@ var flags struct {
 	PrintMetrics  bool          `flag:"metrics,default=$GOCACHE_METRICS,Print summary metrics to stderr at exit"`
 	Expiration    time.Duration `flag:"expiry,default=$GOCACHE_EXPIRY,Cache expiration period (optional)"`
 	Verbose       bool          `flag:"v,default=$GOCACHE_VERBOSE,Enable verbose logging"`
-	DebugLog      bool          `flag:"debug,default=$GOCACHE_DEBUG,Enable detailed per-request debug logging (noisy)"`
+	DebugLog      int           `flag:"debug,default=$GOCACHE_DEBUG,Enable detailed per-request debug logging (noisy)"`
 }
 
+const (
+	debugBuildCache = 1 << iota
+	debugModProxy
+	debugRevProxy
+)
+
 // runDirect runs a cache communicating on stdin/stdout, for use as a direct
 // GOCACHEPROG plugin.
 func runDirect(env *command.Env) error {

cmd/go-cache-plugin/go-cache-plugin.go

@@ -94,7 +94,7 @@ func getBucketRegion(ctx context.Context, bucket string) (string, error) {
 // vprintf acts as log.Printf if the --verbose flag is set; otherwise it
 // discards its input.
 func vprintf(msg string, args ...any) {
-	if flags.Verbose {
+	if flags.Verbose || flags.DebugLog != 0 {
 		log.Printf(msg, args...)
 	}
 }

cmd/go-cache-plugin/help.go

@@ -45,7 +45,7 @@ settings can be set via environment variables as well as flags.
     -c                GOCACHE_CONCURRENCY    int         runtime.NumCPU
     -u                GOCACHE_S3_CONCURRENCY duration    runtime.NumCPU
     -v                GOCACHE_VERBOSE        bool        false
-    --debug           GOCACHE_DEBUG          bool        false
+    --debug           GOCACHE_DEBUG          int         0 (see "help debug")
 
    --------------------------------------------------------------------
    Flag (serve)       Variable               Format      Default
@@ -135,4 +135,17 @@ server generates its own TLS certificate, and tries to install a custom signing
 cert so that other tools will validate it. The ability to do this varies by
 system and configuration, however.`,
 	},
+	{
+		Name: "debug",
+		Help: `Enable detailed debug logging.
+
+The --debug flag enables (very) verbose debug logging for the components of the
+cache plugin. The value of the flag is a bit mask of:
+
+   1:  Go build cache
+   2:  Go module proxy and sum database
+   4:  HTTP reverse proxy
+
+The default is 0 (no debug logging).`,
+	},
 }

cmd/go-cache-plugin/setup.go

@@ -85,7 +85,7 @@ func initCacheServer(env *command.Env) (*gocache.Server, *s3util.Client, error)
 		SetMetrics:  cache.SetMetrics,
 		MaxRequests: flags.Concurrency,
 		Logf:        vprintf,
-		LogRequests: flags.DebugLog,
+		LogRequests: flags.DebugLog&debugBuildCache != 0,
 	}
 	expvar.Publish("gocache_server", s.Metrics().Get("server"))
 	return s, client, nil
@@ -111,7 +111,7 @@ func initModProxy(env *command.Env, s3c *s3util.Client) (_ http.Handler, cleanup
 		KeyPrefix:   path.Join(flags.KeyPrefix, "module"),
 		MaxTasks:    flags.S3Concurrency,
 		Logf:        vprintf,
-		LogRequests: flags.DebugLog,
+		LogRequests: flags.DebugLog&debugModProxy != 0,
 	}
 	cleanup = func() { vprintf("close cacher (err=%v)", cacher.Close()) }
 	proxy := &goproxy.Goproxy{
@@ -163,7 +163,7 @@ func initRevProxy(env *command.Env, s3c *s3util.Client, g *taskgroup.Group) (htt
 		S3Client:    s3c,
 		KeyPrefix:   path.Join(flags.KeyPrefix, "revproxy"),
 		Logf:        vprintf,
-		LogRequests: flags.DebugLog,
+		LogRequests: flags.DebugLog&debugRevProxy != 0,
 	}
 	bridge := &proxyconn.Bridge{
 		Addrs:   hosts,