[processor/k8sattributes] Move "k8sattr.rfc3339" feature gate to Beta

  Time format of `k8s.pod.start_time` attribute value migrated from RFC3339:
  Before: 2023-07-10 12:34:39.740638 -0700 PDT m=+0.020184946
  After: 2023-07-10T12:39:53.112485-07:00
  The feature gate can be temporary reverted back by adding `--feature-gate=-k8sattr.rfc3339` to the command line.

Author: dmitryax

.chloggen/k8sattrs-move-time-format-feature-gate-to-beta.yaml

@@ -0,0 +1,31 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: processor/k8sattributes
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Graduate "k8sattr.rfc3339" feature gate to Beta.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [28817]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  Time format of `k8s.pod.start_time` attribute value migrated from RFC3339:
+  Before: 2023-07-10 12:34:39.740638 -0700 PDT m=+0.020184946
+  After: 2023-07-10T12:39:53.112485-07:00
+  The feature gate can be temporary reverted back by adding `--feature-gate=-k8sattr.rfc3339` to the command line.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

processor/k8sattributesprocessor/internal/kube/client.go

@@ -26,10 +26,10 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/k8sattributesprocessor/internal/observability"
 )
 
-// Upgrade to StageBeta in v0.83.0
+// Upgrade to StageStable in v0.92.0
 var enableRFC3339Timestamp = featuregate.GlobalRegistry().MustRegister(
 	"k8sattr.rfc3339",
-	featuregate.StageAlpha,
+	featuregate.StageBeta,
 	featuregate.WithRegisterDescription("When enabled, uses RFC3339 format for k8s.pod.start_time value"),
 	featuregate.WithRegisterFromVersion("v0.82.0"),
 )

processor/k8sattributesprocessor/processor.go

@@ -50,12 +50,6 @@ func (kp *kubernetesprocessor) initKubeClient(logger *zap.Logger, kubeClient kub
 }
 
 func (kp *kubernetesprocessor) Start(_ context.Context, _ component.Host) error {
-	if kp.rules.StartTime {
-		kp.logger.Warn("k8s.pod.start_time value will be changed to use RFC3339 format in v0.83.0. " +
-			"see https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/24016 for more information. " +
-			"enable feature-gate k8sattr.rfc3339 to opt into this change.")
-	}
-
 	if !kp.passthroughMode {
 		go kp.kc.Start()
 	}