pkg/kgo: add Client.CommitMarkedOffsets

examples/goroutine_per_partition_consuming/autocommit_marks/main.go

@@ -75,7 +75,7 @@ func (s *splitConsume) assigned(_ context.Context, cl *kgo.Client, assigned map[
 
 func (s *splitConsume) revoked(ctx context.Context, cl *kgo.Client, revoked map[string][]int32) {
 	s.killConsumers(revoked)
-	if err := cl.CommitUncommittedOffsets(ctx); err != nil {
+	if err := cl.CommitMarkedOffsets(ctx); err != nil {
 		fmt.Printf("Revoke commit failed: %v\n", err)
 	}
 }

pkg/kgo/consumer_group.go

@@ -2352,8 +2352,42 @@ func (cl *Client) MarkCommitRecords(rs ...*Record) {
 // processing records, you can call this function in a goroutine.
 func (cl *Client) CommitUncommittedOffsets(ctx context.Context) error {
 	// This function is just the tail end of CommitRecords just above.
+	return cl.commitOffsets(ctx, cl.UncommittedOffsets())
+}
+
+// CommitMarkedOffsets issues a synchronous offset commit for any
+// partition that has been consumed from that has marked offsets.
+// Retriable errors are retried up to the configured retry limit, and any
+// unretriable error is returned.
+//
+// This function is useful as a simple way to commit offsets if you have
+// marked offsets with MarkCommitRecords when using AutoCommitMarks. As an
+// alternative if you want to commit specific records, see CommitRecords.
+//
+// Simple usage of this function may lead to duplicate records if a consumer
+// group rebalance occurs before or while this function is being executed. You
+// can avoid this scenario by calling CommitRecords in a custom
+// OnPartitionsRevoked, but for most workloads, a small bit of potential
+// duplicate processing is fine. See the documentation on DisableAutoCommit
+// for more details. You can also avoid this problem by using
+// BlockRebalanceOnCommit, but that option comes with its own tradeoffs (refer
+// to its documentation).
+//
+// The recommended pattern for using this function is to have a poll / process
+// / commit loop. First PollFetches, then process every record,
+// call MarkCommitRecords for the records you wish the commit and then call
+// CommitMarkedOffsets.
+//
+// If you do not want to wait for this function to complete before continuing
+// processing records, you can call this function in a goroutine.
+func (cl *Client) CommitMarkedOffsets(ctx context.Context) error {
+	// This function is just the tail end of CommitRecords just above.
+	return cl.commitOffsets(ctx, cl.MarkedOffsets())
+}
+
+func (cl *Client) commitOffsets(ctx context.Context, offsets map[string]map[int32]EpochOffset) error {
 	var rerr error
-	cl.CommitOffsetsSync(ctx, cl.UncommittedOffsets(), func(_ *Client, _ *kmsg.OffsetCommitRequest, resp *kmsg.OffsetCommitResponse, err error) {
+	cl.CommitOffsetsSync(ctx, offsets, func(_ *Client, _ *kmsg.OffsetCommitRequest, resp *kmsg.OffsetCommitResponse, err error) {
 		if err != nil {
 			rerr = err
 			return