pip_services3_messaging.queues.IMessageQueue module

pip_services3_messaging.queues.IMessageQeueue

Interface for message queues.

copyright:Conceptual Vision Consulting LLC 2018-2019, see AUTHORS for more details.
license:MIT, see LICENSE for more details.
class pip_services3_messaging.queues.IMessageQueue.IMessageQueue

Bases: pip_services3_commons.run.IOpenable.IOpenable, pip_services3_commons.run.IClosable.IClosable

Interface for asynchronous message queues.

Not all queues may implement all the methods. Attempt to call non-supported method will result in NotImplemented exception. To verify if specific method is supported consult with [[MessagingCapabilities]].

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.
begin_listen(correlation_id, receiver)

Listens for incoming messages without blocking the current thread.

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

Gets the queue capabilities

Returns:the queue’s capabilities object.
get_name()

Gets the queue name

Returns:the queue name.
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, envelop)

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.
send_as_object(correlation_id, message_type, message)

Sends an object into the queue. Before sending the object is converted into JSON string and wrapped in a [[MessageEnvelop]].

Parameters:
  • correlation_id – (optional) transaction id to trace execution through call chain.
  • message_type – a message type
  • message – an object value to be sent