feat: observability, IP filtering, stdout/clickhouse fixes (v1.1.11)

- feat(observability): metrics server with /metrics and /health endpoints
- feat(observability): correlation metrics (events, success/failed, reasons, buffers)
- feat(correlation): IP exclusion filter (exact IPs and CIDR ranges)
- feat(correlation): pending orphan delay for late-arriving B events
- fix(stdout): sink is now a no-op for data; JSON must never appear on stdout
- fix(clickhouse): all flush errors were silently discarded, now properly logged
- fix(clickhouse): buffer overflow with DropOnOverflow now logged at WARN
- fix(clickhouse): retry attempts logged at WARN with attempt/delay/error context
- feat(clickhouse): connection success logged at INFO, batch sends at DEBUG
- feat(clickhouse): SetLogger() for external logger injection
- test(stdout): assert stdout remains empty for correlated and orphan logs
- chore(rpm): bump version to 1.1.11, update changelog
- docs: README and architecture.yml updated

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

cmd/logcorrelator/main.go

@@ -1,11 +1,13 @@
 package main
 
 import (
+	"context"
 	"flag"
 	"fmt"
 	"os"
 	"os/signal"
 	"syscall"
+	"time"
 
 	"github.com/logcorrelator/logcorrelator/internal/adapters/inbound/unixsocket"
 	"github.com/logcorrelator/logcorrelator/internal/adapters/outbound/clickhouse"
@@ -88,17 +90,15 @@ func main() {
 			logger.Error("Failed to create ClickHouse sink", err)
 			os.Exit(1)
 		}
+		clickHouseSink.SetLogger(logger)
 		sinks = append(sinks, clickHouseSink)
 		logger.Info(fmt.Sprintf("Configured ClickHouse sink: table=%s", cfg.Outputs.ClickHouse.Table))
 	}
 
 	if cfg.Outputs.Stdout.Enabled {
-		stdoutSink := stdout.NewStdoutSink(stdout.Config{
-			Enabled: true,
-			Level:   cfg.Outputs.Stdout.Level,
-		})
+		stdoutSink := stdout.NewStdoutSink(stdout.Config{Enabled: true})
 		sinks = append(sinks, stdoutSink)
-		logger.Info(fmt.Sprintf("Configured stdout sink: level=%s", cfg.Outputs.Stdout.Level))
+		logger.Info("Configured stdout sink (operational logs on stderr)")
 	}
 
 	// Create multi-sink wrapper
@@ -106,14 +106,15 @@ func main() {
 
 	// Create correlation service
 	correlationSvc := domain.NewCorrelationService(domain.CorrelationConfig{
-		TimeWindow:         cfg.Correlation.GetTimeWindow(),
-		ApacheAlwaysEmit:   cfg.Correlation.GetApacheAlwaysEmit(),
-		ApacheEmitDelayMs:  cfg.Correlation.GetApacheEmitDelayMs(),
-		NetworkEmit:        false,
-		MaxHTTPBufferSize:  cfg.Correlation.GetMaxHTTPBufferSize(),
+		TimeWindow:          cfg.Correlation.GetTimeWindow(),
+		ApacheAlwaysEmit:    cfg.Correlation.GetApacheAlwaysEmit(),
+		ApacheEmitDelayMs:   cfg.Correlation.GetApacheEmitDelayMs(),
+		NetworkEmit:         false,
+		MaxHTTPBufferSize:   cfg.Correlation.GetMaxHTTPBufferSize(),
 		MaxNetworkBufferSize: cfg.Correlation.GetMaxNetworkBufferSize(),
-		NetworkTTLS:        cfg.Correlation.GetNetworkTTLS(),
-		MatchingMode:       cfg.Correlation.GetMatchingMode(),
+		NetworkTTLS:         cfg.Correlation.GetNetworkTTLS(),
+		MatchingMode:        cfg.Correlation.GetMatchingMode(),
+		ExcludeSourceIPs:    cfg.Correlation.GetExcludeSourceIPs(),
 	}, &domain.RealTimeProvider{})
 
 	// Set logger for correlation service
@@ -124,6 +125,27 @@ func main() {
 		cfg.Correlation.GetApacheAlwaysEmit(),
 		cfg.Correlation.GetApacheEmitDelayMs()))
 
+	// Start metrics server if enabled
+	var metricsServer *observability.MetricsServer
+	if cfg.Metrics.Enabled {
+		addr := cfg.Metrics.Addr
+		if addr == "" {
+			addr = ":8080" // Default address
+		}
+		var err error
+		metricsServer, err = observability.NewMetricsServer(addr, correlationSvc.GetMetricsSnapshot)
+		if err != nil {
+			logger.Error("Failed to create metrics server", err)
+			os.Exit(1)
+		}
+		if err := metricsServer.Start(); err != nil {
+			logger.Error("Failed to start metrics server", err)
+			os.Exit(1)
+		}
+		logger.Info(fmt.Sprintf("Metrics server started: addr=%s", metricsServer.Addr()))
+		logger.Info("Metrics endpoints: /metrics (JSON), /health")
+	}
+
 	// Create orchestrator
 	orchestrator := app.NewOrchestrator(app.OrchestratorConfig{
 		Sources: sources,
@@ -166,5 +188,14 @@ func main() {
 		logger.Error("Error during shutdown", err)
 	}
 
+	// Stop metrics server
+	if metricsServer != nil {
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		if err := metricsServer.Stop(shutdownCtx); err != nil {
+			logger.Error("Error stopping metrics server", err)
+		}
+	}
+
 	logger.Info("logcorrelator stopped")
 }