etcd
Distributed reliable key-value store for the most critical data
...It gracefully handles leader elections during network partitions and can tolerate machine failure, even in the leader node. etcd is a consistent distributed key-value store. Mainly used as a separate coordination service, in distributed systems. And designed to hold small amounts of data that can fit entirely in memory. Read and write values using standard HTTP tools, such as curl. Store data in hierarchically organized directories, as in a standard filesystem. Watch specific keys or directories for changes and react to changes in values.