pip_services3_messaging.queues.MemoryMessageQueue module

pip_services3_messaging.queues.MemoryMessageQueue

Memory message queue implementation.

copyright:Conceptual Vision Consulting LLC 2018-2019, see AUTHORS for more details.
license:MIT, see LICENSE for more details.
class pip_services3_messaging.queues.MemoryMessageQueue.MemoryMessageQueue(name=None)

Bases: pip_services3_messaging.queues.MessageQueue.MessageQueue, pip_services3_commons.run.ICleanable.ICleanable

Message queue that sends and receives messages within the same process by using shared memory. This queue is typically used for testing to mock real queues.

### Configuration parameters ###

  • name: name of the message queue

### References ###

  • :logger::*:1.0 (optional) ILogger components to pass log messages
  • :counters::*:1.0 (optional) ICounters components to pass collected measurements
Example:

queue = MessageQueue(“myqueue”) queue.send(“123”, MessageEnvelop(None, “mymessage”, “ABC”))

message = queue.receive(“123”, 0) if message != None:

… queue.complete(“123”, message)
class LockedMessage

Bases: object

lock_expiration = None
abandon(message)

Returnes message into the queue and makes it available for all subscribers to receive it again. This method is usually used to return a message which could not be processed at the moment to repeat the attempt. Messages that cause unrecoverable errors shall be removed permanently or/and send to dead letter queue.

Parameters:message – a message to return.
clear(correlation_id)

Clears component state.

Parameters:correlation_id – (optional) transaction id to trace execution through call chain.
close(correlation_id)

Closes component and frees used resources.

Parameters:correlation_id – (optional) transaction id to trace execution through call chain.
complete(message)

Permanently removes a message from the queue. This method is usually used to remove the message after successful processing.

Parameters:message – a message to remove.
end_listen(correlation_id)

Ends listening for incoming messages. When this method is call [[listen]] unblocks the thread and execution continues.

Parameters:correlation_id – (optional) transaction id to trace execution through call chain.
is_opened()

Checks if the component is opened.

Returns:true if the component has been opened and false otherwise.
listen(correlation_id, receiver)

Listens for incoming messages and blocks the current thread until queue is closed.

Parameters:
  • correlation_id – (optional) transaction id to trace execution through call chain.
  • receiver – a receiver to receive incoming messages.
move_to_dead_letter(message)

Permanently removes a message from the queue and sends it to dead letter queue.

Parameters:message – a message to be removed.
peek(correlation_id)

Peeks a single incoming message from the queue without removing it. If there are no messages available in the queue it returns null.

Parameters:correlation_id – (optional) transaction id to trace execution through call chain.
Returns:a message object.
peek_batch(correlation_id, message_count)

Peeks multiple incoming messages from the queue without removing them. If there are no messages available in the queue it returns an empty list.

Parameters:
  • correlation_id – (optional) transaction id to trace execution through call chain.
  • message_count – a maximum number of messages to peek.
Returns:

a list of message objects.
read_message_count()

Reads the current number of messages in the queue to be delivered.

Returns:a number of messages
receive(correlation_id, wait_timeout)

Receives an incoming message and removes it from the queue.

Parameters:
  • correlation_id – (optional) transaction id to trace execution through call chain.
  • wait_timeout – a timeout in milliseconds to wait for a message to come.
Returns:

a message object.
renew_lock(message, lock_timeout)

Renews a lock on a message that makes it invisible from other receivers in the queue. This method is usually used to extend the message processing time.

Parameters:
  • message – a message to extend its lock.
  • lock_timeout – a locking timeout in milliseconds.
send(correlation_id, message)

Sends a message into the queue.

Parameters:
  • correlation_id – (optional) transaction id to trace execution through call chain.
  • envelop – a message envelop to be sent.