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Added Consumer.OffsetsStore() #72

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merged 4 commits into from
Aug 8, 2017
Merged

Added Consumer.OffsetsStore() #72

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ccda146
Added Consumer.OffsetsStore()
ctrochalakis Jul 10, 2017
72f0b93
fixup! Added Consumer.OffsetsStore()
ctrochalakis Aug 8, 2017
dceec2d
fixup! Added Consumer.OffsetsStore()
ctrochalakis Aug 8, 2017
4c37670
fixup! Added Consumer.OffsetsStore()
ctrochalakis Aug 8, 2017
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23 changes: 23 additions & 0 deletions kafka/consumer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -194,6 +194,29 @@ func (c *Consumer) CommitOffsets(offsets []TopicPartition) ([]TopicPartition, er
return c.commit(offsets)
}

// OffsetsStore stores the provided list of offsets that will be committed
// to the offset store according to `auto.commit.interval.ms` or manual
// offset-less Commit().
//
// Returns the stored offsets on success. If at least one offset couldn't be stored,
// an error and a list of offsets is returned. Each offset can be checked for
// specific errors via its `.Error` member.
func (c *Consumer) OffsetsStore(offsets []TopicPartition) (storedOffsets []TopicPartition, err error) {
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Should probably be called StoreOffsets to be consistent with CommitOffsets (even though it makes it inconsistent with librdkafka, but that's a hidden gem).

coffsets := newCPartsFromTopicPartitions(offsets)
defer C.rd_kafka_topic_partition_list_destroy(coffsets)

cErr := C.rd_kafka_offsets_store(c.handle.rk, coffsets)

// coffsets might be annotated with an error
storedOffsets = newTopicPartitionsFromCparts(coffsets)

if cErr != C.RD_KAFKA_RESP_ERR_NO_ERROR {
return storedOffsets, newError(cErr)
}

return storedOffsets, nil
}

// Seek seeks the given topic partitions using the offset from the TopicPartition.
//
// If timeoutMs is not 0 the call will wait this long for the
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15 changes: 14 additions & 1 deletion kafka/consumer_test.go
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Expand Up @@ -54,7 +54,6 @@ func TestConsumerAPIs(t *testing.T) {
if err != nil {
t.Errorf("SubscribeTopics failed: %s", err)
}

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Remove whitespace diff

_, err = c.Commit()
if err != nil && err.(Error).Code() != ErrNoOffset {
t.Errorf("Commit() failed: %s", err)
Expand All @@ -65,6 +64,20 @@ func TestConsumerAPIs(t *testing.T) {
t.Errorf("Unsubscribe failed: %s", err)
}

topic := "gotest"
stored, err := c.OffsetsStore([]TopicPartition{{Topic: &topic, Partition: 0, Offset: 1}})
if err != nil && err.(Error).Code() != ErrUnknownPartition {
t.Errorf("OffsetsStore() failed: %s", err)
toppar := stored[0]
if toppar.Error.(Error).Code() == ErrUnknownPartition {
t.Errorf("OffsetsStore() TopicPartition error: %s", toppar.Error)
}
}
stored, err = c.OffsetsStore(nil)
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Is there a use for accepting a nil partition set?

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nil is a valid value for a slice, in fact it is the default value. I wanted to make sure it is explicitly handled. In the fixup I changed that to an uninitialized (default) slice.

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Right, the data type allows it, but is there a point for the StoreOffsets API to allow it? Passing a nil slice should be considered a usage error and not something we need to explicitly handle (I do agree that error handling is necessary, but parameter checking in APIs is not as fruitful as it seems IMHO unless there is a security concern to it).

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@ctrochalakis ctrochalakis Aug 8, 2017 •
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Let's call it an empty slice. I think that the API should allow passing an empty slice, whatever that means in Go. If someone chooses to pass an empty slice no error is returned. We don't explicitly handle it (as in consumer.go code) but we explicitly test that an empty []TopicPartition is properly treated.

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note that this part of the diff is now changed to:

        var empty []TopicPartition
        stored, err = c.StoreOffsets(empty)

which seems like a valid usage scenario.

if err != nil {
t.Errorf("OffsetsStore(nil) failed: %s", err)
}

topic1 := "gotest1"
topic2 := "gotest2"
err = c.Assign([]TopicPartition{{Topic: &topic1, Partition: 2},
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