OneCache: A memcached compliant, best-effort, replicated KV store

Datetime:2016-08-23 01:29:09         Topic: Memcached          Share        Original >>
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OneCache is a distributed key/value store that is accessible via the memcached protocol. OneCache nodes natively support clustering and best effort replication. Adding nodes into the cluster effectively increases the in-memory storage capability of the cache. Replication of keys minimizes the impact of a single node failure as requests will transparently be forwarded to the new key leader.

OneCache's architecture is built around the concept of a one-hop distributed hash table. Many DHT algorithms are designed for a very large number of members, such as bitorrent DHTs, and trade lookup efficiency for per-node storage and communication. However, OneCache is built for a much smaller cluster size (<100) and as such, every node holds the full state of the underlying consistent hash ring. This is advantageous because every node is capable of forwarding requests to the correct node, which is why it receives the term one-hop.

OneCache's name then becomes a play on its one-hop DHT architecture and memcached protocol support.

Download pre-compiled binaries by browsing thereleases.

See a micro-benchmark comparing OneCache and memcachedhere.


Single Node

To start a single OneCache node listening on memcached's default port, simply run:

$> ./onecache


To start a cluster of OneCache nodes on a single machine (for ease of getting started) we must bind the nodes to non-default ports to avoid collision. If clustering on different machines, the default ports can be used.

Start the first node in one terminal:

$> ./onecache -gossip_port=7946 -port=11211

In another, start the second and have it join. The output will show it added a peer node.

$> ./onecache -gossip_port=7947 -port=11212 -join=""
2016/01/18 12:04:30 [INFO] onecache: added peer node &{c3f48bd0-4106-43d4-9044-15cf552037f0 11211}


Standard memcached libraries can be used, which make OneCache an easy drop in replacement for memcached as code doesn't have to be changed. OneCache is also accessible via the terminal:

$> telnet 11211
Connected to localhost.
Escape character is '^]'.
set foo 0 0 12
hello, world

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