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 Layers.

The Tower Ecosystem

Tower is made up of the following crates:

• tower (this crate)
• tower-service
• tower-layer
• tower-test

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	Middleware that allows balancing load among multiple services.
buffer	Middleware that provides a buffered mpsc channel to a service.
builder	Builder types to compose layers and services
discover	Service discovery
layer	A collection of Layer based tower services
limit	Tower middleware for limiting requests.
load	Service load measurement
make	Trait aliases for Services that produce specific types of Responses.
ready_cache	A cache of services
timeout	Middleware that applies a timeout to requests.
util	Various utility types and functions that are generally used 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 Services 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.