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Add the field to avoid creating missing topic. #873

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50 changes: 50 additions & 0 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -337,6 +337,7 @@ to use in most cases as it provides additional features:
- Synchronous or asynchronous writes of messages to Kafka.
- Asynchronous cancellation using contexts.
- Flushing of pending messages on close to support graceful shutdowns.
- Creation of a missing topic before publishing a message. *Note!* it was the default behaviour up to the version `v0.4.30`.

```go
// make a writer that produces to topic-A, using the least-bytes distribution
Expand Down Expand Up @@ -369,6 +370,55 @@ if err := w.Close(); err != nil {
}
```

### Missing topic creation before publication

```go
// Make a writer that publishes messages to topic-A.
// The topic will be created if it is missing.
w := &Writer{
Addr: TCP("localhost:9092"),
Topic: "topic-A",
AllowAutoTopicCreation: true,
}

messages := []kafka.Message{
{
Key: []byte("Key-A"),
Value: []byte("Hello World!"),
},
{
Key: []byte("Key-B"),
Value: []byte("One!"),
},
{
Key: []byte("Key-C"),
Value: []byte("Two!"),
},
}

var err error
const retries = 3
for i := 0; i < retries; i++ {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()

// attempt to create topic prior to publishing the message
err = w.WriteMessages(ctx, messages...)
if errors.Is(err, LeaderNotAvailable) || errors.Is(err, context.DeadlineExceeded) {
time.Sleep(time.Millisecond * 250)
continue
}

if err != nil {
log.Fatalf("unexpected error %v", err)
}
}

if err := w.Close(); err != nil {
log.Fatal("failed to close writer:", err)
}
```

### Writing to multiple topics

Normally, the `WriterConfig.Topic` is used to initialize a single-topic writer.
Expand Down
7 changes: 5 additions & 2 deletions writer.go
Original file line number Diff line number Diff line change
Expand Up @@ -185,6 +185,9 @@ type Writer struct {
// If nil, DefaultTransport is used.
Transport RoundTripper

// AllowAutoTopicCreation notifies writer to create topic is missing.
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While it's not a breaking change per-say since the code will continue to compile, the new behavior we introduce is the inverse of what the program used to do.

Do you think we could add a bit more documentation to reflect that fact?

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@kislerdm kislerdm Mar 27, 2022

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@achille-roussel hey! indeed, you are right wrt docu update. I update the test case as well.

AllowAutoTopicCreation bool
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Any reason to not introduce this in the writer config too?
#1278

If I am using WriterConfig to create the writer, is it safe to just set this config after calling NewWriter?

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@erikdw @achille-roussel Here's a PR in case 1278 is a desirable feature request: #1279 if


// Manages the current set of partition-topic writers.
group sync.WaitGroup
mutex sync.Mutex
Expand Down Expand Up @@ -733,7 +736,7 @@ func (w *Writer) partitions(ctx context.Context, topic string) (int, error) {
// caching recent results (the kafka.Transport types does).
r, err := client.transport().RoundTrip(ctx, client.Addr, &metadataAPI.Request{
TopicNames: []string{topic},
AllowAutoTopicCreation: true,
AllowAutoTopicCreation: w.AllowAutoTopicCreation,
})
if err != nil {
return 0, err
Expand Down Expand Up @@ -941,7 +944,7 @@ func newBatchQueue(initialSize int) batchQueue {
bq := batchQueue{
queue: make([]*writeBatch, 0, initialSize),
mutex: &sync.Mutex{},
cond: &sync.Cond{},
cond: &sync.Cond{},
}

bq.cond.L = bq.mutex
Expand Down
29 changes: 29 additions & 0 deletions writer_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -160,6 +160,10 @@ func TestWriter(t *testing.T) {
scenario: "writing a message to a non-existant topic creates the topic",
function: testWriterAutoCreateTopic,
},
{
scenario: "terminates on an attempt to write a message to a nonexistent topic",
function: testWriterTerminateMissingTopic,
},
}

for _, test := range tests {
Expand Down Expand Up @@ -712,6 +716,7 @@ func testWriterAutoCreateTopic(t *testing.T) {
Topic: topic,
Balancer: &RoundRobin{},
})
w.AllowAutoTopicCreation = true
defer w.Close()

msg := Message{Key: []byte("key"), Value: []byte("Hello World")}
Expand All @@ -737,6 +742,30 @@ func testWriterAutoCreateTopic(t *testing.T) {
}
}

func testWriterTerminateMissingTopic(t *testing.T) {
topic := makeTopic()

transport := &Transport{}
defer transport.CloseIdleConnections()

writer := &Writer{
Addr: TCP("localhost:9092"),
Topic: topic,
Balancer: &RoundRobin{},
RequiredAcks: RequireNone,
AllowAutoTopicCreation: false,
Transport: transport,
}
defer writer.Close()

msg := Message{Value: []byte("FooBar")}

if err := writer.WriteMessages(context.Background(), msg); err == nil {
t.Fatal("Kafka error [3] UNKNOWN_TOPIC_OR_PARTITION is expected")
return
}
}

type staticBalancer struct {
partition int
}
Expand Down