remotecfg: set lower poll_frequency limit (#937)

Signed-off-by: Paschalis Tsilias <[email protected]>

CHANGELOG.md

@@ -58,6 +58,9 @@ Main (unreleased)
 
 - Allow override debug metrics level for `otelcol.*` components. (@hainenber)
 
+- Add an initial lower limit of 10 seconds for the the `poll_frequency`
+  argument in the `remotecfg` block. (@tpaschalis)
+
 - Added support for NS records to `discovery.dns`. (@djcode)
 
 ### Bugfixes

docs/sources/reference/config-blocks/remotecfg.md

@@ -50,6 +50,8 @@ If not set, the self-reported `id` that {{< param "PRODUCT_NAME" >}} uses is a r
 The `id` and `metadata` fields are used in the periodic request sent to the
 remote endpoint so that the API can decide what configuration to serve.
 
+The `poll_frequency` must be set to at least `"10s"`.
+
 ## Blocks
 
 The following blocks are supported inside the definition of `remotecfg`:

internal/service/remotecfg/remotecfg.go

@@ -99,6 +99,10 @@ func (a *Arguments) SetToDefault() {
 
 // Validate implements syntax.Validator.
 func (a *Arguments) Validate() error {
+	if a.PollFrequency < 10*time.Second {
+		return fmt.Errorf("poll_frequency must be at least \"10s\", got %q", a.PollFrequency)
+	}
+
 	// We must explicitly Validate because HTTPClientConfig is squashed and it
 	// won't run otherwise
 	if a.HTTPClientConfig != nil {

internal/service/remotecfg/remotecfg_test.go

@@ -70,7 +70,7 @@ func TestAPIResponse(t *testing.T) {
 	env := newTestEnvironment(t)
 	require.NoError(t, env.ApplyConfig(fmt.Sprintf(`
 		url            = "%s"
-		poll_frequency = "10ms"
+		poll_frequency = "10s"
 	`, url)))
 
 	client := &collectorClient{}
@@ -100,7 +100,7 @@ func TestAPIResponse(t *testing.T) {
 	// Verify that the service has loaded the updated response.
 	require.EventuallyWithT(t, func(c *assert.CollectT) {
 		assert.Equal(c, getHash([]byte(cfg2)), env.svc.getCfgHash())
-	}, time.Second, 10*time.Millisecond)
+	}, 1*time.Second, 10*time.Millisecond)
 }
 
 func buildGetConfigHandler(in string) func(context.Context, *connect.Request[collectorv1.GetConfigRequest]) (*connect.Response[collectorv1.GetConfigResponse], error) {
@@ -138,6 +138,10 @@ func (env *testEnvironment) ApplyConfig(config string) error {
 	if err := syntax.Unmarshal([]byte(config), &args); err != nil {
 		return err
 	}
+	// The lower limit of the poll_frequency argument would slow our tests
+	// considerably; let's artificially lower it after the initial validation
+	// has taken place.
+	args.PollFrequency /= 100
 	return env.svc.Update(args)
 }