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0.4.0 Jan 31, 2021
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0.2.2 Jan 18, 2021
0.1.0 Jan 10, 2021

#223 in Asynchronous

Download history 33/week @ 2021-01-08 96/week @ 2021-01-15 31/week @ 2021-01-22 45/week @ 2021-01-29 499/week @ 2021-02-05 1545/week @ 2021-02-12 1463/week @ 2021-02-19

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Used in lifeline

MIT license

420KB
6K SLoC

The feature-rich, portable async channel library > crates.io > docs.rs

Why use Postage?

  • Includes a rich set of channels. | barrier | broadcast | dispatch | mpsc | oneshot | watch
  • Works with any executor.
    • Currently regressions are written for tokio and async-std.
    • With the futures-traits feature, channels implement the futures Sink/Stream traits.
  • Throughly tested.
    • Channels have full unit test coverage, and integration test coverage with multiple async executors.
  • Includes built-in Sink and Stream combinators.
    • Sinks can be chained and filtered.
    • Streams can be chained, filtered, mapped, and merged.
    • Sinks and streams can log their values, for easy app debugging.

Channels

postage::barrier

Barrier channels can be used to synchronize events, but do not transmit any data. When the sender is dropped (or tx.send(()) is called), the receiver is awoken. This can be used to asynchronously coordinate actions between tasks.

postage::broadcast

The broadcast channel provides reliable broadcast delivery between multiple senders and multiple receivers. The channel has a fixed capacity, and senders are suspended if the buffer is filled.

When a receiver is cloned, both receivers will be sent the same series of messages.

Senders also provide a subscribe() method which creates a receiver that will observe all messages sent after the call to subscribe.

postage::dispatch

The dispatch channel provides multi-sender, multi-receiver message dispatch. A message will be observed by at most one reciever. The channel has a fixed capacity, and senders are suspended if the buffer is filled.

Receivers can be created with rx.clone(), or tx.subscribe().

postage::mpsc

Postage includes a fixed-capacity multi-producer, single-consumer channel. The producer can be cloned, and the sender task is suspended if the channel becomes full.

postage::oneshot

Oneshot channels transmit a single value between a sender and a reciever. Neither can be cloned. If the sender drops, the receiver recieves a None value.

postage::watch

Watch channels can be used to asynchronously transmit state. When receivers are created, they immediately recieve an initial value. They will also recieve new values, but are not guaranteed to recieve every value.

Values transmitted over watch channels must implement Default. A simple way to achieve this is to transmit Option<T>.

Benchmarks

Benchmarks of postage channels, and comparable async-std/tokio channels.

  • send/recv measures the total time to send and receive an item.
  • send full measures the time to send an item and get a Poll::Pending value on a full channel.
  • recv empty measures the time to get a Poll::Pending value on an empty channel.

All benchmarks were taken with criterion and are in the benches directory.

Package Channel send/recv send full recv empty
broadcast postage 144ns 6ns 7ns
broadcast tokio 88ns (-38%) 49ns 39ns
-
dispatch postage 87ns 26ns 26ns
dispatch async_std 41ns (-52%) 10ns 10ns
-
mpsc postage 79ns 25ns 27ns
mpsc tokio 132ns (+67%) 1ns 31ns
-
watch postage 96ns - 7ns
watch tokio 74ns (-22%) - 75ns

Dependencies

~0.7–1.4MB
~29K SLoC