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本文主要聊一下spring for kafka的retry

AbstractRetryingMessageListenerAdapter

spring-kafka-1.2.3.RELEASE-sources.jar!/org/springframework/kafka/listener/adapter/AbstractRetryingMessageListenerAdapter.java
主要有两个实现类RetryingAcknowledgingMessageListenerAdapter以及RetryingMessageListenerAdapter

RetryingAcknowledgingMessageListenerAdapter

public class RetryingAcknowledgingMessageListenerAdapter<K, V>
        extends AbstractRetryingMessageListenerAdapter<K, V, AcknowledgingMessageListener<K, V>>
        implements AcknowledgingMessageListener<K, V> {

    private final AcknowledgingMessageListener<K, V> delegate;

    /**
     * Construct an instance with the provided template and delegate. The exception will
     * be thrown to the container after retries are exhausted.
     * @param messageListener the listener delegate.
     * @param retryTemplate the template.
     */
    public RetryingAcknowledgingMessageListenerAdapter(AcknowledgingMessageListener<K, V> messageListener,
            RetryTemplate retryTemplate) {
        this(messageListener, retryTemplate, null);
    }

    /**
     * Construct an instance with the provided template, callback and delegate.
     * @param messageListener the listener delegate.
     * @param retryTemplate the template.
     * @param recoveryCallback the recovery callback; if null, the exception will be
     * thrown to the container after retries are exhausted.
     */
    public RetryingAcknowledgingMessageListenerAdapter(AcknowledgingMessageListener<K, V> messageListener,
            RetryTemplate retryTemplate, RecoveryCallback<? extends Object> recoveryCallback) {
        super(messageListener, retryTemplate, recoveryCallback);
        Assert.notNull(messageListener, "'messageListener' cannot be null");
        this.delegate = messageListener;
    }

    @SuppressWarnings("unchecked")
    @Override
    public void onMessage(final ConsumerRecord<K, V> record, final Acknowledgment acknowledgment) {
        getRetryTemplate().execute(new RetryCallback<Object, KafkaException>() {

            @Override
            public Void doWithRetry(RetryContext context) throws KafkaException {
                context.setAttribute(CONTEXT_RECORD, record);
                context.setAttribute(CONTEXT_ACKNOWLEDGMENT, acknowledgment);
                RetryingAcknowledgingMessageListenerAdapter.this.delegate.onMessage(record, acknowledgment);
                return null;
            }

        }, (RecoveryCallback<Object>) getRecoveryCallback());
    }

}

RetryingMessageListenerAdapter

spring-kafka-1.2.3.RELEASE-sources.jar!/org/springframework/kafka/listener/adapter/RetryingMessageListenerAdapter.java

public class RetryingMessageListenerAdapter<K, V>
        extends AbstractRetryingMessageListenerAdapter<K, V, MessageListener<K, V>>
        implements MessageListener<K, V> {

    /**
     * Construct an instance with the provided template and delegate. The exception will
     * be thrown to the container after retries are exhausted.
     * @param messageListener the delegate listener.
     * @param retryTemplate the template.
     */
    public RetryingMessageListenerAdapter(MessageListener<K, V> messageListener, RetryTemplate retryTemplate) {
        this(messageListener, retryTemplate, null);
    }

    /**
     * Construct an instance with the provided template, callback and delegate.
     * @param messageListener the delegate listener.
     * @param retryTemplate the template.
     * @param recoveryCallback the recovery callback; if null, the exception will be
     * thrown to the container after retries are exhausted.
     */
    public RetryingMessageListenerAdapter(MessageListener<K, V> messageListener, RetryTemplate retryTemplate,
            RecoveryCallback<? extends Object> recoveryCallback) {
        super(messageListener, retryTemplate, recoveryCallback);
        Assert.notNull(messageListener, "'messageListener' cannot be null");
    }

    @SuppressWarnings("unchecked")
    @Override
    public void onMessage(final ConsumerRecord<K, V> record) {
        getRetryTemplate().execute(new RetryCallback<Object, KafkaException>() {

            @Override
            public Void doWithRetry(RetryContext context) throws KafkaException {
                context.setAttribute(CONTEXT_RECORD, record);
                RetryingMessageListenerAdapter.this.delegate.onMessage(record);
                return null;
            }

        }, (RecoveryCallback<Object>) getRecoveryCallback());
    }

}

具体是哪种listener呢

spring-kafka-1.2.3.RELEASE-sources.jar!/org/springframework/kafka/config/AbstractKafkaListenerEndpoint.java

private void setupMessageListener(MessageListenerContainer container, MessageConverter messageConverter) {
        Object messageListener = createMessageListener(container, messageConverter);
        Assert.state(messageListener != null, "Endpoint [" + this + "] must provide a non null message listener");
        if (this.retryTemplate != null) {
            if (messageListener instanceof AcknowledgingMessageListener) {
                messageListener = new RetryingAcknowledgingMessageListenerAdapter<>(
                        (AcknowledgingMessageListener<K, V>) messageListener, this.retryTemplate,
                        this.recoveryCallback);
            }
            else {
                messageListener = new RetryingMessageListenerAdapter<>((MessageListener<K, V>) messageListener,
                        this.retryTemplate, (RecoveryCallback<Object>) this.recoveryCallback);
            }
        }
        if (this.recordFilterStrategy != null) {
            if (messageListener instanceof AcknowledgingMessageListener) {
                messageListener = new FilteringAcknowledgingMessageListenerAdapter<>(
                        (AcknowledgingMessageListener<K, V>) messageListener, this.recordFilterStrategy,
                        this.ackDiscarded);
            }
            else if (messageListener instanceof MessageListener) {
                messageListener = new FilteringMessageListenerAdapter<>((MessageListener<K, V>) messageListener,
                        this.recordFilterStrategy);
            }
            else if (messageListener instanceof BatchAcknowledgingMessageListener) {
                messageListener = new FilteringBatchAcknowledgingMessageListenerAdapter<>(
                        (BatchAcknowledgingMessageListener<K, V>) messageListener, this.recordFilterStrategy,
                        this.ackDiscarded);
            }
            else if (messageListener instanceof BatchMessageListener) {
                messageListener = new FilteringBatchMessageListenerAdapter<>(
                        (BatchMessageListener<K, V>) messageListener, this.recordFilterStrategy);
            }
        }
        container.setupMessageListener(messageListener);
    }

如果retryTemplate不为null的话，会先判断是不是AcknowledgingMessageListener的子类，如果是则创建RetryingAcknowledgingMessageListenerAdapter，如果不是则创建RetryingMessageListenerAdapter

spring-kafka-1.2.3.RELEASE-sources.jar!/org/springframework/kafka/config/MethodKafkaListenerEndpoint.java

protected MessagingMessageListenerAdapter<K, V> createMessageListenerInstance(MessageConverter messageConverter) {
        if (isBatchListener()) {
            BatchMessagingMessageListenerAdapter<K, V> messageListener = new BatchMessagingMessageListenerAdapter<K, V>(
                    this.bean, this.method);
            if (messageConverter instanceof BatchMessageConverter) {
                messageListener.setBatchMessageConverter((BatchMessageConverter) messageConverter);
            }
            return messageListener;
        }
        else {
            RecordMessagingMessageListenerAdapter<K, V> messageListener =
                    new RecordMessagingMessageListenerAdapter<K, V>(this.bean, this.method);
            if (messageConverter instanceof RecordMessageConverter) {
                messageListener.setMessageConverter((RecordMessageConverter) messageConverter);
            }
            return messageListener;
        }
    }

其中RecordMessagingMessageListenerAdapter实现了AcknowledgingMessageListener接口

public class RecordMessagingMessageListenerAdapter<K, V> extends MessagingMessageListenerAdapter<K, V>
        implements MessageListener<K, V>, AcknowledgingMessageListener<K, V> {
        //......
}