apply: Allow ignoring a specific error returned from updatePartitions()

When applying topic's configuration, we'd like to be able
avoid failing in case the desired topic's partition count
is smaller than the actual topic's partitions count (on
the broker).
We know that Kafka doesn't allow partitions decrease,
so instead of failing the operation we'd like to
continue without doing anything.
This is very convenient when trying to apply a batch
of topics in which case, we don't want to fail the rest
of the batch for one topic that its partition count
configuration is lower than the actual partitions count.

This change is backward compatible, as the default behavior
is kept.

Signed-off-by: shimon-armis <[email protected]>

cmd/topicctl/subcmd/apply.go

@@ -35,6 +35,7 @@ type applyCmdConfig struct {
 	autoContinueRebalance        bool
 	retentionDropStepDurationStr string
 	skipConfirm                  bool
+	ignoreFewerPartitionsError   bool
 	sleepLoopDuration            time.Duration
 
 	shared sharedOptions
@@ -99,6 +100,12 @@ func init() {
 		false,
 		"Skip confirmation prompts during apply process",
 	)
+	applyCmd.Flags().BoolVar(
+		&applyConfig.ignoreFewerPartitionsError,
+		"ignore-fewer-partitions-error",
+		false,
+		"Don't return error when topic's config specifies fewer partitions than it currently has",
+	)
 	applyCmd.Flags().DurationVar(
 		&applyConfig.sleepLoopDuration,
 		"sleep-loop-duration",
@@ -231,6 +238,7 @@ func applyTopic(
 			AutoContinueRebalance:      applyConfig.autoContinueRebalance,
 			RetentionDropStepDuration:  applyConfig.retentionDropStepDuration,
 			SkipConfirm:                applyConfig.skipConfirm,
+			IgnoreFewerPartitionsError: applyConfig.ignoreFewerPartitionsError,
 			SleepLoopDuration:          applyConfig.sleepLoopDuration,
 			TopicConfig:                topicConfig,
 		}

pkg/apply/apply.go

@@ -34,6 +34,7 @@ type TopicApplierConfig struct {
 	AutoContinueRebalance      bool
 	RetentionDropStepDuration  time.Duration
 	SkipConfirm                bool
+	IgnoreFewerPartitionsError bool
 	SleepLoopDuration          time.Duration
 	TopicConfig                config.TopicConfig
 }
@@ -194,6 +195,10 @@ func (t *TopicApplier) applyNewTopic(ctx context.Context) error {
 	return nil
 }
 
+func isFewerPartitionsError(err error) bool {
+	return strings.Contains(err.Error(), "Fewer partitions in topic config")
+}
+
 func (t *TopicApplier) applyExistingTopic(
 	ctx context.Context,
 	topicInfo admin.TopicInfo,
@@ -213,6 +218,11 @@ func (t *TopicApplier) applyExistingTopic(
 	}
 
 	if err := t.updatePartitions(ctx, topicInfo); err != nil {
+		if isFewerPartitionsError(err) && t.config.IgnoreFewerPartitionsError {
+			log.Warnf("UpdatePartitions failure ignored. topic: %v, error: %v", t.topicName, err)
+			return nil
+		}
+
 		return err
 	}