io.cdap.cdap.api.messaging

Interface MessageFetcher

@Beta
public interface MessageFetcher

Provides message fetching functions of the Transactional Messaging System.

Method Summary

Modifier and Type	Method and Description
CloseableIterator<Message>	fetch(String namespace, String topic, int limit, long timestamp) Fetches messages from the given topic that were published on or after the given timestamp.
CloseableIterator<Message>	fetch(String namespace, String topic, int limit, String afterMessageId) Fetches messages from the given topic that were published after a message, identified by the given message id.

Method Detail

fetch

CloseableIterator<Message> fetch(String namespace,
                                 String topic,
                                 int limit,
                                 long timestamp)
                          throws TopicNotFoundException,
                                 IOException

Fetches messages from the given topic that were published on or after the given timestamp.

Parameters:

namespace - namespace of the topic

topic - name of the topic

limit - maximum number of messages to fetch

timestamp - timestamp in milliseconds; the publish timestamp of the first Message returned by the resulting CloseableIterator will be on or after the given timestamp. Use timestamp = 0 to poll from the first available message.

Returns:

a CloseableIterator of Message

Throws:

IllegalArgumentException - if the topic name is invalid. A valid id should only contain alphanumeric characters, _, or -.

IOException - if there was a failure to communicate with the messaging system

TopicNotFoundException - if the give topic doesn't exist

fetch

CloseableIterator<Message> fetch(String namespace,
                                 String topic,
                                 int limit,
                                 @Nullable
                                 String afterMessageId)
                          throws TopicNotFoundException,
                                 IOException

Fetches messages from the given topic that were published after a message, identified by the given message id.

Parameters:

namespace - namespace of the topic

topic - name of the topic

limit - maximum number of messages to fetch

afterMessageId - message id returned from the Message.getId() method from a prior call to one of the pollMessages methods. If it is null, it will fetch from the first available message.

Returns:

a CloseableIterator of Message

Throws:

IllegalArgumentException - if the topic name is invalid. A valid id should only contain alphanumeric characters, _, or -.

IOException - if there was a failure to communicate with the messaging system

TopicNotFoundException - if the give topic doesn't exist