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Cluster version is the min major.minor of all members in the etcd cluster. Cluster version is set to the min version that a etcd member is compatible with when first bootstrapp. During a rolling upgrades, the cluster version will be updated automatically. For example: ``` Cluster [a:1, b:1 ,c:1] -> clusterVersion 1 update a -> 2, b -> 2 after a detection Cluster [a:2, b:2 ,c:1] -> clusterVersion 1, since c is still 1 update c -> 2 after a detection Cluster [a:2, b:2 ,c:2] -> clusterVersion 2 ``` The API/raft component can utilize clusterVersion to determine if it can accept a client request or a raft RPC. We choose polling rather than pushing since we want to use the same logic for cluster version detection and (TODO) cluster version checking. Before a member actually joins a etcd cluster, it should check the version of the cluster. Push does not work since the other members cannot push version info to it before it actually joins. Moreover, we do not want our raft RPC system (which is doing the heartbeat pushing) to coordinate cluster version.
etcd
etcd is a distributed, consistent key value store for shared configuration and service discovery with a focus on being:
- Simple: curl'able user facing API (HTTP+JSON)
- Secure: optional SSL client cert authentication
- Fast: benchmarked 1000s of writes/s per instance
- Reliable: properly distributed using Raft
etcd is written in Go and uses the Raft consensus algorithm to manage a highly-available replicated log.
See etcdctl for a simple command line client. Or feel free to just use curl, as in the examples below.
If you're considering etcd for production use, please see: production-ready.md
Getting Started
Getting etcd
The latest release and setup instructions are available at GitHub.
You can build a latest etcd from master branch. All development occurs on the master branch which includes new features and bug fixes.
Bug fixes should target the master branch and ported to the appropriate release branch as described in the branch management guide.
Running etcd
First start a single-member cluster of etcd:
./bin/etcd
This will bring up etcd listening on port 2379 for client communication and on port 2380 for server-to-server communication.
Next, let's set a single key, and then retrieve it:
curl -L http://127.0.0.1:2379/v2/keys/mykey -XPUT -d value="this is awesome"
curl -L http://127.0.0.1:2379/v2/keys/mykey
You have successfully started an etcd and written a key to the store.
Running local etcd cluster
First install goreman, which manages Procfile-based applications.
Our Procfile script will set up a local example cluster. You can start it with:
goreman start
This will bring up 3 etcd members infra1, infra2 and infra3 and etcd proxy proxy, which runs locally and composes a cluster.
You can write a key to the cluster and retrieve the value back from any member or proxy.
Next Steps
Now it's time to dig into the full etcd API and other guides.
- Explore the full API.
- Set up a multi-machine cluster.
- Learn the config format, env variables and flags.
- Find language bindings and tools.
- Use TLS to secure an etcd cluster.
- Tune etcd.
- Upgrade from 0.4.6 to 2.0.0.
Contact
- Mailing list: etcd-dev
- IRC: #coreos on freenode.org
- Planning/Roadmap: milestones
- Bugs: issues
Contributing
See CONTRIBUTING for details on submitting patches and the contribution workflow.
Project Details
Versioning
Service Versioning
etcd uses semantic versioning New minor versions may add additional features to the API.
You can get the version of etcd by issuing a request to /version:
curl -L http://127.0.0.1:2379/version
API Versioning
The v2 API responses should not change after the 2.0.0 release but new features will be added over time.
32-bit systems
etcd has known issues on 32-bit systems due to a bug in the Go runtime. See #358 for more information.
License
etcd is under the Apache 2.0 license. See the LICENSE file for details.