[][src]Module tokio::sync::mpsc

A multi-producer, single-consumer queue for sending values across asynchronous tasks.

Similar to std, channel creation provides Receiver and Sender handles. Receiver implements Stream and allows a task to read values out of the channel. If there is no message to read, the current task will be notified when a new value is sent. Sender implements the Sink trait and allows sending messages into the channel. If the channel is at capacity, the send is rejected and the task will be notified when additional capacity is available. In other words, the channel provides backpressure.

Unbounded channels are also available using the unbounded_channel constructor.


When all Sender handles have been dropped, it is no longer possible to send values into the channel. This is considered the termination event of the stream. As such, Receiver::poll returns Ok(Ready(None)).

If the Receiver handle is dropped, then messages can no longer be read out of the channel. In this case, all further attempts to send will result in an error.

Clean Shutdown

When the Receiver is dropped, it is possible for unprocessed messages to remain in the channel. Instead, it is usually desirable to perform a "clean" shutdown. To do this, the receiver first calls close, which will prevent any further messages to be sent into the channel. Then, the receiver consumes the channel to completion, at which point the receiver can be dropped.



Channel error types



Receive values from the associated Sender.


Send values to the associated Receiver.


Receive values from the associated UnboundedSender.


Send values to the associated UnboundedReceiver.



Create a bounded mpsc channel for communicating between asynchronous tasks, returning the sender/receiver halves.


Create an unbounded mpsc channel for communicating between asynchronous tasks.