feat: add support for static extra fields for JSON logs

Fixes #7356

Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>

hack/release.toml

@@ -177,6 +177,22 @@ kind: WatchdogTimerConfig
 device: /dev/watchdog0
 timeout: 3m0s
 ```
+"""
+
+    [notes.logging]
+        title = "Logging"
+        description = """\
+Talos Linux now supports setting extra tags when sending logs in JSON format:
+
+```yaml
+machine:
+  logging:
+    destinations:
+      - endpoint: "udp://127.0.0.1:12345/"
+        format: "json_lines"
+        extraTags:
+          server: s03-rack07
+```
 """
 
 [make_deps]

internal/app/machined/pkg/controllers/runtime/kmsg_log.go

@@ -23,6 +23,8 @@ import (
 	networkutils "github.com/siderolabs/talos/internal/app/machined/pkg/controllers/network/utils"
 	machinedruntime "github.com/siderolabs/talos/internal/app/machined/pkg/runtime"
 	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime/logging"
+	"github.com/siderolabs/talos/pkg/machinery/config/config"
+	"github.com/siderolabs/talos/pkg/machinery/constants"
 	"github.com/siderolabs/talos/pkg/machinery/resources/network"
 	"github.com/siderolabs/talos/pkg/machinery/resources/runtime"
 )
@@ -110,14 +112,33 @@ func (ctrl *KmsgLogDeliveryController) Run(ctx context.Context, r controller.Run
 	}
 }
 
+type logConfig struct {
+	endpoint *url.URL
+}
+
+func (c logConfig) Format() string {
+	return constants.LoggingFormatJSONLines
+}
+
+func (c logConfig) Endpoint() *url.URL {
+	return c.endpoint
+}
+
+func (c logConfig) ExtraTags() map[string]string {
+	return nil
+}
+
 //nolint:gocyclo
 func (ctrl *KmsgLogDeliveryController) deliverLogs(ctx context.Context, r controller.Runtime, logger *zap.Logger, kmsgCh <-chan kmsg.Packet, destURLs []*url.URL) error {
 	if ctrl.drainSub == nil {
 		ctrl.drainSub = ctrl.Drainer.Subscribe()
 	}
 
 	// initialize all log senders
-	senders := xslices.Map(destURLs, logging.NewJSONLines)
+	destLogConfigs := xslices.Map(destURLs, func(u *url.URL) config.LoggingDestination {
+		return logConfig{endpoint: u}
+	})
+	senders := xslices.Map(destLogConfigs, logging.NewJSONLines)
 
 	defer func() {
 		closeCtx, closeCtxCancel := context.WithTimeout(context.Background(), logCloseTimeout)

internal/app/machined/pkg/runtime/logging/sender_jsonlines.go

@@ -13,24 +13,28 @@ import (
 	"time"
 
 	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime"
+	"github.com/siderolabs/talos/pkg/machinery/config/config"
 )
 
 type jsonLinesSender struct {
-	endpoint *url.URL
+	endpoint  *url.URL
+	extraTags map[string]string
 
 	sema chan struct{}
 	conn net.Conn
 }
 
 // NewJSONLines returns log sender that sends logs in JSON over TCP (newline-delimited)
 // or UDP (one message per packet).
-func NewJSONLines(endpoint *url.URL) runtime.LogSender {
+func NewJSONLines(cfg config.LoggingDestination) runtime.LogSender {
 	sema := make(chan struct{}, 1)
 	sema <- struct{}{}
 
 	return &jsonLinesSender{
-		endpoint: endpoint,
-		sema:     sema,
+		endpoint:  cfg.Endpoint(),
+		extraTags: cfg.ExtraTags(),
+
+		sema: sema,
 	}
 }
 
@@ -55,6 +59,10 @@ func (j *jsonLinesSender) marshalJSON(e *runtime.LogEvent) ([]byte, error) {
 	m["talos-time"] = e.Time.Format(time.RFC3339Nano)
 	m["talos-level"] = e.Level.String()
 
+	for k, v := range j.extraTags {
+		m[k] = v
+	}
+
 	return json.Marshal(m)
 }