Add the ability to send logs to a syslog daemon.

README.md

···
     * If `SENTRY_DSN` environment variable is set, panics are reported to Sentry.
     * If `SENTRY_DSN` and `SENTRY_LOGS=1` environment variables are set, logs are uploaded to Sentry.
     * If `SENTRY_DSN` and `SENTRY_TRACING=1` environment variables are set, traces are uploaded to Sentry.
+* Optional syslog integration allows transmitting application logs to a syslog daemon. When present, the `SYSLOG_ADDR` environment variable enables the integration, and the variable's value is used to configure the absolute path to a Unix socket (usually located at `/dev/log` on Unix systems) or a network address of one of the following formats:
+    * for TLS over TCP: `tcp+tls://host:port`;
+    * for plain TCP: `tcp://host:post`;
+    * for UDP: `udp://host:port`.
 
 
 Architecture (v2)

go.mod

···
 
 require (
 	codeberg.org/git-pages/go-headers v1.1.0
+	codeberg.org/git-pages/go-slog-syslog v0.0.0-20251122140925-40467958039d
 	github.com/KimMachineGun/automemlimit v0.7.5
 	github.com/c2h5oh/datasize v0.0.0-20231215233829-aa82cc1e6500
 	github.com/creasty/defaults v1.8.0
···
 	github.com/kevinburke/ssh_config v1.4.0 // indirect
 	github.com/klauspost/cpuid/v2 v2.3.0 // indirect
 	github.com/klauspost/crc32 v1.3.0 // indirect
+	github.com/leodido/go-syslog/v4 v4.3.0 // indirect
 	github.com/minio/crc64nvme v1.1.0 // indirect
 	github.com/minio/md5-simd v1.1.2 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect

go.sum

···
 codeberg.org/git-pages/go-headers v1.1.0 h1:rk7/SOSsn+XuL7PUQZFYUaWKHEaj6K8mXmUV9rF2VxE=
 codeberg.org/git-pages/go-headers v1.1.0/go.mod h1:N4gwH0U3YPwmuyxqH7xBA8j44fTPX+vOEP7ejJVBPts=
+codeberg.org/git-pages/go-slog-syslog v0.0.0-20251122140501-cef0168bba20 h1:gwBA9NToHbaExklHIdOvjc4gzVJkDeffHxlsPY64NrM=
+codeberg.org/git-pages/go-slog-syslog v0.0.0-20251122140501-cef0168bba20/go.mod h1:8NPSXbYcVb71qqNM5cIgn1/uQgMisLbu2dVD1BNxsUw=
+codeberg.org/git-pages/go-slog-syslog v0.0.0-20251122140925-40467958039d h1:+U2YyXy2QX8oe1e5+UFR1PXfgIK79QWgAgM9l9FQG5o=
+codeberg.org/git-pages/go-slog-syslog v0.0.0-20251122140925-40467958039d/go.mod h1:8NPSXbYcVb71qqNM5cIgn1/uQgMisLbu2dVD1BNxsUw=
 github.com/KimMachineGun/automemlimit v0.7.5 h1:RkbaC0MwhjL1ZuBKunGDjE/ggwAX43DwZrJqVwyveTk=
 github.com/KimMachineGun/automemlimit v0.7.5/go.mod h1:QZxpHaGOQoYvFhv/r4u3U0JTC2ZcOwbSr11UZF46UBM=
 github.com/Microsoft/go-winio v0.6.2 h1:F2VQgta7ecxGYO8k3ZZz3RS8fVIXVxONVUPlNERoyfY=
···
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
 github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
+github.com/leodido/go-syslog/v4 v4.3.0 h1:bbSpI/41bYK9iSdlYzcwvlxuLOE8yi4VTFmedtnghdA=
+github.com/leodido/go-syslog/v4 v4.3.0/go.mod h1:eJ8rUfDN5OS6dOkCOBYlg2a+hbAg6pJa99QXXgMrd98=
 github.com/maypok86/otter/v2 v2.2.1 h1:hnGssisMFkdisYcvQ8L019zpYQcdtPse+g0ps2i7cfI=
 github.com/maypok86/otter/v2 v2.2.1/go.mod h1:1NKY9bY+kB5jwCXBJfE59u+zAwOt6C7ni1FTlFFMqVs=
 github.com/minio/crc64nvme v1.1.0 h1:e/tAguZ+4cw32D+IO/8GSf5UVr9y+3eJcxZI2WOO/7Q=

src/observe.go

···
 	"runtime/debug"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	slogmulti "github.com/samber/slog-multi"
+
+	syslog "codeberg.org/git-pages/go-slog-syslog"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
···
 		NativeHistogramMinResetDuration: 10 * time.Minute,
 	}, []string{"method"})
 )
+
+var syslogHandler syslog.Handler
 
 func hasSentry() bool {
 	return os.Getenv("SENTRY_DSN") != ""
···
 		log.Println("unknown log format", config.LogFormat)
 	}
 
+	if syslogAddr := os.Getenv("SYSLOG_ADDR"); syslogAddr != "" {
+		var err error
+		syslogHandler, err = syslog.NewHandler(&syslog.HandlerOptions{
+			Address:          syslogAddr,
+			AppName:          "git-pages",
+			StructuredDataID: "git-pages",
+		})
+		if err != nil {
+			log.Fatalf("syslog: %v", err)
+		}
+		logHandlers = append(logHandlers, syslogHandler)
+	}
+
 	if hasSentry() {
 		enableLogs := false
 		if value, err := strconv.ParseBool(os.Getenv("SENTRY_LOGS")); err == nil {
···
 }
 
 func FiniObservability() {
+	var wg sync.WaitGroup
+	timeout := 2 * time.Second
+	if syslogHandler != nil {
+		wg.Go(func() { syslogHandler.Flush(timeout) })
+	}
 	if hasSentry() {
-		sentry.Flush(2 * time.Second)
+		wg.Go(func() { sentry.Flush(timeout) })
 	}
+	wg.Wait()
 }
 
 func ObserveError(err error) {