fix: reduce idle runner polling by default

Raise the default idle fetch backoff ceiling to reduce steady-state FetchTask traffic from idle runner fleets while keeping the value configurable for installations that need faster idle polling.

Fixes: https://gitea.com/gitea/runner/issues/762

Co-Authored-By: GPT-5 Codex <codex@openai.com>

internal/pkg/config/config.example.yaml

@@ -39,7 +39,7 @@ runner:
   # The maximum interval for fetching the job from the Gitea instance.
   # The runner uses exponential backoff when idle, increasing the interval up to this maximum.
   # Set to 0 or same as fetch_interval to disable backoff.
-  fetch_interval_max: 5s
+  fetch_interval_max: 1m
   # While idle, remove stale bind-workdir task directories and orphaned host-mode
   # scratch directories (left behind when a host cleanup delete stalls) older than
   # this duration. Setting either workdir_cleanup_age or idle_cleanup_interval to 0

internal/pkg/config/config.go

@@ -183,7 +183,7 @@ func LoadDefault(file string) (*Config, error) {
 		cfg.Runner.FetchInterval = 2 * time.Second
 	}
 	if cfg.Runner.FetchIntervalMax <= 0 {
-		cfg.Runner.FetchIntervalMax = 5 * time.Second
+		cfg.Runner.FetchIntervalMax = time.Minute
 	}
 	if cfg.Runner.WorkdirCleanupAge == 0 && !definedRunnerKeys["workdir_cleanup_age"] {
 		cfg.Runner.WorkdirCleanupAge = 24 * time.Hour

internal/pkg/config/config_test.go

@@ -48,6 +48,12 @@ func TestLoadDefault_DefaultsWorkdirCleanupAge(t *testing.T) {
 	assert.Equal(t, 10*time.Minute, cfg.Runner.IdleCleanupInterval)
 }
 
+func TestLoadDefault_DefaultsIdleFetchBackoffMax(t *testing.T) {
+	cfg, err := LoadDefault("")
+	require.NoError(t, err)
+	assert.Equal(t, time.Minute, cfg.Runner.FetchIntervalMax)
+}
+
 func TestLoadDefault_UsesConfiguredWorkdirCleanupAge(t *testing.T) {
 	dir := t.TempDir()
 	path := filepath.Join(dir, "config.yaml")