fix(loki.rules.kubernetes, mimir.rules.kubernetes): add timeout to ruler sync calls

Add a 30s context timeout to the ListRules calls in syncLoki and
syncMimir to prevent the event loop goroutine from blocking indefinitely
when the remote ruler is unreachable (e.g. due to a firewall blackhole).

The shared RulerSyncTimeout constant is defined once in the common
kubernetes package and reused by both components.

Author: QuentinBisson

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Bug Fixes 🐛
+
+* **loki.rules.kubernetes, mimir.rules.kubernetes:** Add a 30s timeout to remote ruler sync (ListRules) calls to prevent the event loop from hanging indefinitely on transient network issues.
+
 ## [1.15.0](https://github.com/grafana/alloy/compare/v1.14.0...v1.15.0) (2026-03-26)
 
 

internal/component/common/kubernetes/event.go

@@ -1,6 +1,8 @@
 package kubernetes
 
 import (
+	"time"
+
 	"github.com/go-kit/log"
 	"github.com/grafana/alloy/internal/runtime/logging/level"
 	"k8s.io/client-go/tools/cache"
@@ -18,6 +20,11 @@ type EventType string
 
 const (
 	EventTypeResourceChanged EventType = "resource-changed"
+
+	// RulerSyncTimeout is the timeout applied to remote ruler API calls (e.g.
+	// listing rule groups) to prevent the event loop from blocking indefinitely
+	// on transient network issues.
+	RulerSyncTimeout = 30 * time.Second
 )
 
 type queuedEventHandler struct {

internal/component/loki/rules/kubernetes/events.go

@@ -80,6 +80,9 @@ func (c *Component) processEvent(ctx context.Context, e kubernetes.Event) error
 }
 
 func (c *Component) syncLoki(ctx context.Context) error {
+	ctx, cancel := context.WithTimeout(ctx, kubernetes.RulerSyncTimeout)
+	defer cancel()
+
 	rulesByNamespace, err := c.lokiClient.ListRules(ctx, "")
 	if err != nil {
 		level.Error(c.log).Log("msg", "failed to list rules from loki", "err", err)

internal/component/mimir/rules/kubernetes/events.go

@@ -123,6 +123,9 @@ func (e *eventProcessor) enqueueSyncMimir() {
 }
 
 func (e *eventProcessor) syncMimir(ctx context.Context) error {
+	ctx, cancel := context.WithTimeout(ctx, kubernetes.RulerSyncTimeout)
+	defer cancel()
+
 	rulesByNamespace, err := e.mimirClient.ListRules(ctx, "")
 	if err != nil {
 		level.Error(e.logger).Log("msg", "failed to list rules from mimir", "err", err)