pkg/kgo: inject fake fetches on metadata load errors

A consumer should be notified when it cannot make progress due to
metadata load errors. We now
* unconditionally inject a fake fetch if a load error is not retryable
* inject a fake fetch if the user has configured KeepRetryableFetchErrors

pkg/kgo/consumer.go

@@ -354,7 +354,7 @@ func NewErrFetch(err error) Fetches {
 		Topics: []FetchTopic{{
 			Topic: "",
 			Partitions: []FetchPartition{{
-				Partition: 0,
+				Partition: -1,
 				Err:       err,
 			}},
 		}},
@@ -384,11 +384,11 @@ func (cl *Client) PollFetches(ctx context.Context) Fetches {
 }
 
 // PollRecords waits for records to be available, returning as soon as any
-// broker returns records in a fetch. If the context is nil, this function
-// will return immediately with any currently buffered records.
+// broker returns records in a fetch. If the context is nil, this function will
+// return immediately with any currently buffered records.
 //
 // If the client is closed, a fake fetch will be injected that has no topic, a
-// partition of 0, and a partition error of ErrClientClosed. If the context is
+// partition of -1, and a partition error of ErrClientClosed. If the context is
 // canceled, a fake fetch will be injected with ctx.Err. These injected errors
 // can be used to break out of a poll loop.
 //

pkg/kgo/consumer_direct_test.go

@@ -9,6 +9,8 @@ import (
 	"sync/atomic"
 	"testing"
 	"time"
+
+	"github.com/twmb/franz-go/pkg/kerr"
 )
 
 // Allow adding a topic to consume after the client is initialized with nothing
@@ -541,3 +543,29 @@ func TestSetOffsetsForNewTopic(t *testing.T) {
 		cl.Close()
 	}
 }
+
+func TestIssue648(t *testing.T) {
+	t.Parallel()
+	cl, _ := newTestClient(
+		MetadataMinAge(100*time.Millisecond),
+		ConsumeTopics("bizbazbuz"),
+		FetchMaxWait(time.Second),
+		KeepRetryableFetchErrors(),
+	)
+	defer cl.Close()
+	ctx, cancel := context.WithTimeout(context.Background(), 4*time.Second)
+	fs := cl.PollFetches(ctx)
+	cancel()
+
+	var found bool
+	fs.EachError(func(_ string, _ int32, err error) {
+		if !errors.Is(err, kerr.UnknownTopicOrPartition) {
+			t.Errorf("expected ErrUnknownTopicOrPartition, got %v", err)
+		} else {
+			found = true
+		}
+	})
+	if !found {
+		t.Errorf("did not see ErrUnknownTopicOrPartition")
+	}
+}

pkg/kgo/metadata.go

@@ -695,6 +695,10 @@ func (cl *Client) mergeTopicPartitions(
 			for _, topicPartition := range lv.partitions {
 				topicPartition.records.bumpRepeatedLoadErr(lv.loadErr)
 			}
+		} else {
+			if !kerr.IsRetriable(r.loadErr) || cl.cfg.keepRetryableFetchErrors {
+				cl.consumer.addFakeReadyForDraining(topic, -1, r.loadErr, "metadata refresh has a load error on this entire topic")
+			}
 		}
 		retryWhy.add(topic, -1, r.loadErr)
 		return
@@ -753,7 +757,7 @@ func (cl *Client) mergeTopicPartitions(
 		}
 		newTP := r.partitions[part]
 
-		// Like above for the entire topic, an individual partittion
+		// Like above for the entire topic, an individual partition
 		// can have a load error. Unlike for the topic, individual
 		// partition errors are always retryable.
 		//
@@ -765,6 +769,10 @@ func (cl *Client) mergeTopicPartitions(
 			newTP.loadErr = err
 			if isProduce {
 				newTP.records.bumpRepeatedLoadErr(newTP.loadErr)
+			} else {
+				if !kerr.IsRetriable(newTP.loadErr) || cl.cfg.keepRetryableFetchErrors {
+					cl.consumer.addFakeReadyForDraining(topic, int32(part), newTP.loadErr, "metadata refresh has a load error on this partition")
+				}
 			}
 			retryWhy.add(topic, int32(part), newTP.loadErr)
 			continue