fix(worker): add metrics HTTP server and health checks for Kubernetes (#7860)

* feat(worker): add metrics HTTP server and debug profiling support

- Add -metricsPort flag to enable Prometheus metrics endpoint
- Add -metricsIp flag to configure metrics server bind address
- Implement /metrics endpoint for Prometheus-compatible metrics
- Implement /health endpoint for Kubernetes readiness/liveness probes
- Add -debug flag to enable pprof debugging server
- Add -debug.port flag to configure debug server port
- Fix stats package import naming conflict by using alias
- Update usage examples to show new flags

Fixes #7843

* feat(helm): add worker metrics and health check support

- Update worker readiness probe to use httpGet on /health endpoint
- Update worker liveness probe to use httpGet on /health endpoint
- Add metricsPort flag to worker command in deployment template
- Support both httpGet and tcpSocket probe types for backward compatibility
- Update values.yaml with health check configuration

This enables Kubernetes pod lifecycle management for worker components through
proper health checks on the new metrics HTTP endpoint.

* feat(mini): align all services to share single debug and metrics servers

- Disable S3's separate debug server in mini mode (port 6060 now shared by all)
- Add metrics server startup to embedded worker for health monitoring
- All services now share the single metrics port (9327) and single debug port (6060)
- Consistent pattern with master, filer, volume, webdav services

* fix(worker): fix variable shadowing in health check handler

- Rename http.ResponseWriter parameter from 'w' to 'rw' to avoid shadowing
  the outer 'w *worker.Worker' parameter
- Prevents potential bugs if future code tries to use worker state in handler
- Improves code clarity and follows Go best practices

* fix(worker): remove unused worker parameter in metrics server

- Change 'w *worker.Worker' parameter to '_' as it's not used
- Clarifies intent that parameter is intentionally unused
- Follows Go best practices and improves code clarity

* fix(helm): fix trailing backslash syntax errors in worker command

- Fix conditional backslash placement to prevent shell syntax errors
- Only add backslash when metricsPort OR extraArgs are present
- Prevents worker pod startup failures due to malformed command arguments
- Ensures proper shell command parsing regardless of configuration state

* refactor(worker): use standard stats.StartMetricsServer for consistency

- Replace custom metrics server implementation with stats.StartMetricsServer
  to match pattern used in master, volume, s3, filer_sync components
- Simplifies code and improves maintainability
- Uses glog.Fatal for errors (consistent with other SeaweedFS components)
- Remove unused net/http and prometheus/promhttp imports
- Automatically provides /metrics and /health endpoints via standard implementation

weed/command/mini.go

@@ -233,8 +233,9 @@ func initMiniS3Flags() {
 	miniS3Options.iamConfig = miniIamConfig
 	miniS3Options.auditLogConfig = cmdMini.Flag.String("s3.auditLogConfig", "", "path to the audit log config file")
 	miniS3Options.allowDeleteBucketNotEmpty = miniS3AllowDeleteBucketNotEmpty
-	miniS3Options.debug = cmdMini.Flag.Bool("s3.debug", false, "serves runtime profiling data via pprof")
-	miniS3Options.debugPort = cmdMini.Flag.Int("s3.debug.port", 6060, "http port for debugging")
+	// In mini mode, S3 uses the shared debug server started at line 681, not its own separate debug server
+	miniS3Options.debug = new(bool) // explicitly false
+	miniS3Options.debugPort = cmdMini.Flag.Int("s3.debug.port", 6060, "http port for debugging (unused in mini mode)")
 }
 
 // initMiniWebDAVFlags initializes WebDAV server flag options
@@ -1060,6 +1061,10 @@ func startMiniWorker() {
 	// Set admin client
 	workerInstance.SetAdminClient(adminClient)
 
+	// Start metrics server for health checks and monitoring (uses shared metrics port like other services)
+	// This allows Kubernetes probes to check worker health via /health endpoint
+	go stats_collect.StartMetricsServer(*miniMetricsHttpIp, *miniMetricsHttpPort)
+
 	// Start the worker
 	err = workerInstance.Start()
 	if err != nil {