com.github.ddth.queue

Interface IQueue

All Known Implementing Classes:

JdbcQueue

public interface IQueue

APIs to interact with queue.

Queue implementation flow:

1. take() message from queue.
2. Do something with the message.
   1. If done with the message, call finish(IQueueMessage).
   2. Otherwise, call requeue(IQueueMessage) or requeueSilent(IQueueMessage) to requeue the message.

Since:

0.1.0

Author:

Thanh Ba Nguyen

Method Summary

Methods

Modifier and Type	Method and Description
int	ephemeralSize() Gets ephemeral-storage's number of items.
void	finish(IQueueMessage msg) Called when finish processing the message to cleanup ephemeral storage.
Collection<IQueueMessage>	getOrphanMessages(long thresholdTimestampMs) Gets all orphan messages (messages that were left in ephemeral storage for a long time).
boolean	moveFromEphemeralToQueueStorage(IQueueMessage msg) Moves a message from ephemeral back to queue storage.
boolean	queue(IQueueMessage msg) Queues a message.
int	queueSize() Gets queue's number of items.
boolean	requeue(IQueueMessage msg) Re-queues a message.
boolean	requeueSilent(IQueueMessage msg) Silently re-queues a message.
IQueueMessage	take() Takes a message out of queue.

Method Detail

queue

boolean queue(IQueueMessage msg)

Queues a message.

Implementation flow:

• Put message to tail of queue storage.

Parameters:

msg -

Returns:

requeue

boolean requeue(IQueueMessage msg)

Re-queues a message.

Implementation flow:

• Put message to tail of queue storage; and increase message's re-queue & update message's queue timestamp. count.
• Remove message from ephemeral storage.

Note: ephemeral storage implementation is optional, depends on implementation.

Parameters:

msg -

Returns:

requeueSilent

boolean requeueSilent(IQueueMessage msg)

Silently re-queues a message.

Implementation flow:

• Put message to tail of queue storage; do NOT increase message's re-queue count or update message's queue timestamp.
• Remove message from ephemeral storage.

Note: ephemeral storage implementation is optional, depends on implementation.

Parameters:

msg -

Returns:

finish

void finish(IQueueMessage msg)

Called when finish processing the message to cleanup ephemeral storage.

Implementation flow:

• Remove message from ephemeral storage.

Note: ephemeral storage implementation is optional, depends on implementation.

Parameters:

msg -

take

IQueueMessage take()

Takes a message out of queue.

Implementation flow:

• Read message from head of queue storage.
• Write message to ephemeral storage.
• Remove message from queue storage.

Note: ephemeral storage implementation is optional, depends on implementation.

Returns:

getOrphanMessages

Collection<IQueueMessage> getOrphanMessages(long thresholdTimestampMs)

Gets all orphan messages (messages that were left in ephemeral storage for a long time).

Parameters:

thresholdTimestampMs - get all orphan messages that were queued before this timestamp

Returns:

Since:

0.2.0

moveFromEphemeralToQueueStorage

boolean moveFromEphemeralToQueueStorage(IQueueMessage msg)

Moves a message from ephemeral back to queue storage. Useful when dealing with orphan messages.

Implementation flow:

• Read message from the ephemeral storage.
• Re-queue the message.
• (message is removed from the ephemeral storage).

Parameters:

msg -

Returns:

true if a move has been made, false otherwise (e.g. the message didn't exist in ephemeral storage)

Since:

0.2.1

queueSize

int queueSize()

Gets queue's number of items.

Returns:

ephemeralSize

int ephemeralSize()

Gets ephemeral-storage's number of items.

Note: ephemeral storage implementation is optional, depends on implementation.

Returns: