Links for 2014-04-18

  • Consul

    Nice-looking new tool from Hashicorp; service discovery and configuration service, built on Raft for leader election, Serf for gossip-based messaging, and Go. Some features: * Gossip is performed over both TCP and UDP; * gossip messages are encrypted symmetrically and therefore secure from eavesdropping, tampering, spoofing and packet corruption (like the incident which brought down S3 for days: http://status.aws.amazon.com/s3-20080720.html ); * exposes both a HTTP interface and (even better) DNS; * includes explicit support for long-distance WAN operation as well as on LANs. It all looks very practical and usable. MPL-licensed. The only potential risk I can see is that expecting to receive config updates from a blocking poll of the HTTP interface needs some good “best practice” docs, to ensure that people don’t mishandle the scenario where there is a network partition between your calling code and the Consul server/agent. Without any heartbeating protocol behind the scenes, HTTP is vulnerable to “hung connections” which would result in a config change being silently missed by the client until the connection eventually is timed out, either by the calling code or the client-side kernel. This could potentially take minutes to occur, which in some usage scenarios could be a big, unforeseen problem.

    (tags: configuration service-discovery distcomp raft consensus-algorithms go mpl open-source dns http gossip-protocol hashicorp)

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