KafkaBundle

Configuration and use of KafkaBundle are based on the RdKafka extension. To consume messages, we decided to use the high level consumer., _(*1)

Kafka documentation, _(*2)

Installation

For Symfony

{
    "require": {
        "m6web/kafka-bundle": "~0.1",
    }
}

// app/AppKernel.php

public function registerBundles()
{
    $bundles = array(
        new M6Web\Bundle\KafkaBundle\M6WebKafkaBundle(),
    );
}

Install the bundle:, _(*4)

$ composer update m6web/kafka-bundle

Usage

Add the m6_web_kafka section in your configuration file., _(*5)

By default, the sf3 event dispatcher will throw an event on each command. To disable this feature:, _(*6)

m6_web_kafka:
   event_dispatcher: false

Here a configuration example:, _(*7)

Librdkafka global configuration properties, _(*8)

m6_web_kafka:
    event_dispatcher: true
    producers:
       producer1:
           configuration:
               timeout.ms: 1000
               queue.buffering.max.ms: 0 # Maximum time, in milliseconds, for buffering data on the producer queue. 1000ms by default. 
           brokers:
               - '127.0.0.1'
               - '10.05.05.19'
           log_level: 3
           events_poll_timeout: 2000 #ms
           topics:
               batman:
                   configuration:
                       retries: 3
                   strategy_partition: 2
               catwoman:
                   configuration:
                       retries: 3
                   strategy_partition: 2

    consumers:
        consumer1:
            configuration:
                metadata.broker.list: '127.0.0.1'
                group.id: 'myConsumerGroup'
                enable.auto.commit: 0
            topicConfiguration:
                auto.offset.reset: 'smallest'
            timeout_consuming_queue: 200
            topics:
                - batman
                - catwoman

Note that we decided to use the high level consumer. So you can set the "group.id" option in the consumer configuration., _(*9)

configuration:
  metadata.broker.list: '127.0.0.1'
  group.id: 'myConsumerGroup'

For the producers, we have one topic configuration for each topic:, _(*10)

 topics:
   batman:
       configuration:
           retries: 3
       strategy_partition: '2'
   catwoman:
       configuration:
           retries: 3
       strategy_partition: '2'
 ```

Whereas for the consumers, we have one topic configuration for all topics:
```yaml
topicConfiguration:
    auto.offset.reset: 'smallest'
timeout_consuming_queue: 200
topics:
    - batman
    - catwoman
 ```

### Producer

A producer will be used to send messages to the server.

In the Kafka Model, messages are sent to topics partitioned and stored on brokers.
This means that in the configuration for a producer you will have to specify the brokers and the topics.
You can optionnaly configure the log level and the strategy partitioner.

Because of RdKafka extension limitations, you cannot configure the partitions number or replication factor from the bundle. 
You must do that from the command line.

After setting your producers with their options, you will be able to produce a message using the `produce` method :

```php
$producer->produce('message', RD_KAFKA_PARTITION_UA, '12345');

The first argument is the message to send.
The second argument is the partition where to produce the message. By default, the value is RD_KAFKA_PARTITION_UA which means that the message will be sent to a random partition.
The third argument is a key if the strategy partitioner is by key.

The RD_KAFKA_PARTITION_UA constant is used according the strategy partitioner. - If the strategy partitioner is random (RD_KAFKA_MSG_PARTITIONER_RANDOM), messages are assigned to partitions randomly. - If the stratefy partitioner is consistent (RD_KAFKA_MSG_PARTITIONER_CONSISTENT) with a key defined, messages are assigned to the partition whose the id maps the hash of the key. If there is no key defined, messages are assigned to the same partition., _(*11)

Consumer

A consumer will be used to get a message from different topics. You can choose to set only one topic by consumer., _(*12)

In the Kafka Model, messages are consumed from topics partitioned and stored on brokers. This means that for a consumer you will have to specify the brokers and topics in the configuration., _(*13)

To consume messages, you will have to use the consume method to consume a message:, _(*14)

$consumer->consume();

The messages will be automatically committed except if there is an error. But you can choose not to do it by adding an argument as following:, _(*15)

$consumer->consume(false);

You can decide to commit manually your message with:, _(*16)

$consumer->commit();

It will commit the last consumed message., _(*17)

It will give you an object \RdKafka\Message with information about the message : payload, topic, or partition for instance. It is the \RdKafka\Message from the RdKafka extension., _(*18)

In case there is no more message, it will give you a No more message string. In case there is a time out, it will give you a Time out string., _(*19)