[−][src]Crate tower

async fn(Request) -> Result<Response, Error>

Overview

Tower is a library of modular and reusable components for building robust networking clients and servers.

Tower provides a simple core abstraction, the Service trait, which represents an asynchronous function taking a request and returning either a response or an error. This abstraction can be used to model both clients and servers.

Generic components, like timeouts, rate limiting, and load balancing, can be modeled as Services that wrap some inner service and apply additional behavior before or after the inner service is called. This allows implementing these components in a protocol-agnostic, composable way. Typically, such services are referred to as middleware.

An additional abstraction, the Layer trait, is used to compose middleware with Services. If a Service can be thought of as an asynchronous function from a request type to a response type, a Layer is a function taking a Service of one type and returning a Service of a different type. The ServiceBuilder type is used to add middleware to a service by composing it with multiple multiple Layers.

The Tower Ecosystem

Tower is made up of the following crates:

Since the Service and Layer traits are important integration points for all libraries using Tower, they are kept as stable as possible, and breaking changes are made rarely. Therefore, they are defined in separate crates, tower-service and tower-layer. This crate contains re-exports of those core traits, implementations of commonly-used middleware, and utilities for working with Services and Layers. Finally, the tower-test crate provides tools for testing programs using Tower.

Usage

The various middleware implementations provided by this crate are feature flagged, so that users can only compile the parts of Tower they need. By default, all the optional middleware are disabled.

To get started using all of Tower's optional middleware, add this to your Cargo.toml:

tower = { version = "0.4", features = ["full"] }

Alternatively, you can only enable some features. For example, to enable only the retry and timeout middleware, write:

tower = { version = "0.4", features = ["retry", "timeout"] }

See here for a complete list of all middleware provided by Tower.

Modules

balance	`balance` Middleware that allows balancing load among multiple services.
buffer	`buffer` Middleware that provides a buffered mpsc channel to a service.
builder	Builder types to compose layers and services
discover	`discover` Service discovery
filter	`filter` Conditionally dispatch requests to the inner service based on the result of a predicate.
hedge	`hedge` Pre-emptively retry requests which have been outstanding for longer than a given latency percentile.
layer	A collection of `Layer` based tower services
limit	`limit` Tower middleware for limiting requests.
load	`load` Service load measurement
load_shed	`load-shed` Middleware for shedding load when inner services aren't ready.
make	`make` Trait aliases for Services that produce specific types of Responses.
ready_cache	`ready-cache` A cache of services
reconnect	`reconnect` Reconnect services when they fail.
retry	`retry` Middleware for retrying "failed" requests.
spawn_ready	`spawn-ready` When an underlying service is not ready, drive it to readiness on a background task.
steer	`steer` This module provides functionality to aid managing routing requests between `Service`s.
timeout	`timeout` Middleware that applies a timeout to requests.
util	`util` Various utility types and functions that are generally with Tower.

Structs

ServiceBuilder

Declaratively construct Service values.

Traits

Layer	Decorates a `Service`, transforming either the request or the response.
MakeService	Creates new `Service` values.
Service	An asynchronous function from a `Request` to a `Response`.
ServiceExt	An extension trait for `Service`s that provides a variety of convenient adapters

Functions

service_fn

Returns a new ServiceFn with the given closure.

Type Definitions

BoxError

Alias for a type-erased error type.