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.

See MessagingCapabilities, MessageEnvelope

abandon(message: pip_services3_messaging.queues.MessageEnvelope.MessageEnvelope)

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: Optional[str], receiver: <module 'pip_services3_messaging.queues.IMessageReceiver' from '/pip_services3_messaging/queues/IMessageReceiver.py'>)

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: pip_services3_messaging.queues.MessageEnvelope.MessageEnvelope)

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: Optional[str])

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() → <module ‘pip_services3_messaging.queues.MessagingCapabilities’ from ‘/pip_services3_messaging/queues/MessagingCapabilities.py’>

Gets the queue capabilities

Returns

the queue’s capabilities object.

get_name() → str

Gets the queue name

Returns

the queue name.

listen(correlation_id: Optional[str], receiver: <module 'pip_services3_messaging.queues.IMessageReceiver' from '/pip_services3_messaging/queues/IMessageReceiver.py'>)

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: pip_services3_messaging.queues.MessageEnvelope.MessageEnvelope)

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

Parameters

message – a message to be removed.

peek(correlation_id: Optional[str]) → pip_services3_messaging.queues.MessageEnvelope.MessageEnvelope

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: Optional[str], message_count: int) → List[pip_services3_messaging.queues.MessageEnvelope.MessageEnvelope]

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() → int

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

Returns

a number of messages

receive(correlation_id: Optional[str], wait_timeout: int) → pip_services3_messaging.queues.MessageEnvelope.MessageEnvelope

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: pip_services3_messaging.queues.MessageEnvelope.MessageEnvelope, lock_timeout: int)

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: Optional[str], envelop: pip_services3_messaging.queues.MessageEnvelope.MessageEnvelope)

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: Optional[str], message_type: str, message: Any)

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

Parameters

  • correlation_id – (optional) transaction id to trace execution through call chain.

  • message_type – a message type

  • message – an object value to be sent