io.openmessaging.consumer

Interface StreamingConsumer

All Superinterfaces:

ServiceLifecycle

public interface StreamingConsumer
extends ServiceLifecycle

A StreamingConsumer provides low level APIs to open multiple streams from a specified queue and then retrieve messages from them through @{code StreamingIterator}. A Queue is consists of multiple streams, the Stream is an abstract concept and can be associated with partition in most messaging systems.

Since:

OMS 1.0.0

Version:

OMS 1.0.0

Method Summary

Modifier and Type	Method and Description
KeyValue	attributes() Returns the attributes of this StreamingConsumer instance.
StreamingIterator	seek(String streamName, String position) Creates a StreamingIterator from the fixed position of the specified stream.
StreamingIterator	seekToBeginning(String streamName) Creates a StreamingIterator from the begin position of the specified stream.
StreamingIterator	seekToEnd(String streamName) Creates a StreamingIterator from the end position of the specified stream.

Methods inherited from interface io.openmessaging.ServiceLifecycle

shutdown, startup

Method Detail

attributes

KeyValue attributes()

Returns the attributes of this StreamingConsumer instance. Changes to the return KeyValue are not reflected in physical StreamingConsumer.

There are some standard attributes defined by OMS for StreamingConsumer:

• OMSBuiltinKeys.CONSUMER_ID, the unique consumer id for a consumer instance.
• OMSBuiltinKeys.OPERATION_TIMEOUT, the default timeout period for operations of StreamingConsumer.

Returns:

the attributes

seekToEnd

StreamingIterator seekToEnd(String streamName)

Creates a StreamingIterator from the end position of the specified stream.

Parameters:

streamName - the specified stream

Returns:

a message iterator at the begin position.

seekToBeginning

StreamingIterator seekToBeginning(String streamName)

Creates a StreamingIterator from the begin position of the specified stream.

Parameters:

streamName - the specified stream

Returns:

a message iterator at the begin position.

seek

StreamingIterator seek(String streamName,
                       String position)

Creates a StreamingIterator from the fixed position of the specified stream.

Creates a StreamingIterator from the begin position if the given position is earlier than the first message's store position in this stream.

Creates a StreamingIterator from the end position, if the given position is later than the last message's store position in this stream.

The position is a String value, may represented by timestamp, offset, cursor, even a casual key.

Parameters:

streamName - the specified stream

position - the specified position

Returns:

a message iterator at the specified position