A distributed, reliable key-value store for the most critical data of a distributed system
Read and write values using standard HTTP tools, such as curl
Store data in hierarchically organized directories, as in a standard filesystem
Watch for changes
Watch specific keys or directories for changes and react to changes in values
Optional SSL client certificate authentication
Benchmarked at 1000s of writes/s per instance
Optional TTLs for keys expiration
Properly distributed via Raft protocol
What is etcd?
etcd is a strongly consistent, distributed key-value store that provides a reliable way to store data that needs to be accessed by a distributed system or cluster of machines. It gracefully handles leader elections during network partitions and can tolerate machine failure, even in the leader node.
Applications of any complexity, from a simple web app to Kubernetes, can read data from and write data into etcd.
Your applications can read from and write data into etcd. A simple use case is storing database connection details or feature flags in etcd as key-value pairs. These values can be watched, allowing your app to reconfigure itself when they change. Advanced uses take advantage of etcd’s consistency guarantees to implement database leader elections or perform distributed locking across a cluster of workers.
etcd is written in Go, which has excellent cross-platform support, small binaries and a great community behind it. Communication between etcd machines is handled via the Raft consensus algorithm.
Latency from the etcd leader is the most important metric to track and the built-in dashboard has a view dedicated to this. In our testing, severe latency will introduce instability within the cluster because Raft is only as fast as the slowest machine in the majority. You can mitigate this issue by properly tuning the cluster. etcd has been pre-tuned on cloud providers with highly variable networks.
A template for PostgreSQL HA with ZooKeeper, etcd, or Consul
A transparent, highly scalable and cryptographically verifiable data store, created by Google
etcd is a Cloud Native Computing Foundation project.