Crate etcd

Expand description

Crate etcd provides a client for etcd, a distributed key-value store from CoreOS.

The client uses etcd’s v2 API. Support for the v3 API is planned, and will be added via separate types for backwards compatibility and to support both APIs simultaneously.

The client uses asynchronous I/O, backed by the futures and tokio crates, and requires both to be used alongside. Where possible, futures are returned using “impl Trait” instead of boxing.

The client is tested against etcd 2.3.8.

Usage

Client is an HTTP client required for all API calls. It can be constructed to use HTTP or HTTPS, and supports authenticating to the etcd cluster via HTTP basic authentication (username and password) and/or X.509 client certificates.

To get basic information about the health and versions of etcd running in a cluster, use the Client::health and Client::versions methods, respectively. All other API calls are made by passing a Client reference to the functions in the auth, kv, members, and stats modules. These modules contain functions for API calls to the authentication and authorization API, the primary key-value store API, the cluster membership API, and statistics API, respectively.

Examples

Basic usage:

use etcd::Client;
use etcd::kv::{self, Action};
use futures::Future;
use tokio::runtime::Runtime;

fn main() {
    // Create a client to access a single cluster member. Addresses of multiple cluster
    // members can be provided and the client will try each one in sequence until it
    // receives a successful response.
    let client = Client::new(&["http://etcd.example.com:2379"], None).unwrap();

    // Set the key "/foo" to the value "bar" with no expiration.
    let work = kv::set(&client, "/foo", "bar", None).and_then(move |_| {
        // Once the key has been set, ask for details about it.
        let get_request = kv::get(&client, "/foo", kv::GetOptions::default());

        get_request.and_then(|response| {
            // The information returned tells you what kind of operation was performed.
            assert_eq!(response.data.action, Action::Get);

            // The value of the key is what we set it to previously.
            assert_eq!(response.data.node.value, Some("bar".to_string()));

            // Each API call also returns information about the etcd cluster extracted from
            // HTTP response headers.
            assert!(response.cluster_info.etcd_index.is_some());

            Ok(())
        })
    });

    // Start the event loop, driving the asynchronous code to completion.
    assert!(Runtime::new().unwrap().block_on(work).is_ok());
}