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

k8s/charts/seaweedfs/templates/worker/worker-deployment.yaml

@@ -138,7 +138,10 @@ spec:
               {{- end }}
               -capabilities={{ .Values.worker.capabilities }} \
               -maxConcurrent={{ .Values.worker.maxConcurrent }} \
-              -workingDir={{ .Values.worker.workingDir }}{{- if .Values.worker.extraArgs }} \{{ end }}
+              -workingDir={{ .Values.worker.workingDir }}{{- if or .Values.worker.metricsPort .Values.worker.extraArgs }} \{{ end }}
+              {{- if .Values.worker.metricsPort }}
+              -metricsPort={{ .Values.worker.metricsPort }}{{- if .Values.worker.extraArgs }} \{{ end }}
+              {{- end }}
               {{- range $index, $arg := .Values.worker.extraArgs }}
               {{ $arg }}{{- if lt $index (sub (len $.Values.worker.extraArgs) 1) }} \{{ end }}
               {{- end }}
@@ -187,9 +190,13 @@ spec:
           {{- end }}
           {{- if .Values.worker.livenessProbe.enabled }}
           livenessProbe:
-            {{- with .Values.worker.livenessProbe.tcpSocket }}
+            {{- if .Values.worker.livenessProbe.httpGet }}
+            httpGet:
+              path: {{ .Values.worker.livenessProbe.httpGet.path }}
+              port: {{ .Values.worker.livenessProbe.httpGet.port }}
+            {{- else if .Values.worker.livenessProbe.tcpSocket }}
             tcpSocket:
-              port: {{ .port }}
+              port: {{ .Values.worker.livenessProbe.tcpSocket.port }}
             {{- end }}
             initialDelaySeconds: {{ .Values.worker.livenessProbe.initialDelaySeconds }}
             periodSeconds: {{ .Values.worker.livenessProbe.periodSeconds }}
@@ -199,9 +206,13 @@ spec:
           {{- end }}
           {{- if .Values.worker.readinessProbe.enabled }}
           readinessProbe:
-            {{- with .Values.worker.readinessProbe.tcpSocket }}
+            {{- if .Values.worker.readinessProbe.httpGet }}
+            httpGet:
+              path: {{ .Values.worker.readinessProbe.httpGet.path }}
+              port: {{ .Values.worker.readinessProbe.httpGet.port }}
+            {{- else if .Values.worker.readinessProbe.tcpSocket }}
             tcpSocket:
-              port: {{ .port }}
+              port: {{ .Values.worker.readinessProbe.tcpSocket.port }}
             {{- end }}
             initialDelaySeconds: {{ .Values.worker.readinessProbe.initialDelaySeconds }}
             periodSeconds: {{ .Values.worker.readinessProbe.periodSeconds }}

k8s/charts/seaweedfs/values.yaml

@@ -1302,10 +1302,11 @@ worker:
   extraEnvironmentVars: {}
 
   # Health checks for worker pods
-  # Since workers do not have an HTTP endpoint, a tcpSocket probe on the metrics port is recommended.
+  # Workers expose metrics on the metricsPort with a /health endpoint for readiness checks.
   livenessProbe:
     enabled: true
-    tcpSocket:
+    httpGet:
+      path: /health
       port: metrics
     initialDelaySeconds: 30
     periodSeconds: 60
@@ -1315,7 +1316,8 @@ worker:
 
   readinessProbe:
     enabled: true
-    tcpSocket:
+    httpGet:
+      path: /health
       port: metrics
     initialDelaySeconds: 20
     periodSeconds: 15