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Experimental support for Akka Remoting and Cluster is now available!

31 Aug 2014

Dear users, we are really happy to announce that our efforts on bringing support for Akka remoting and cluster to Kamon have finally arrived to a point where we can share a working feature with you!

Initially our plans were to deliver support for remoting and cluster in two releases from now 0.2.6/0.3.6 but during the last few months we received requests for this feature from many of our users, so we decided to deliver a experimental version earlier than what we initially expected and, if possible, ship this at least as experimental in 0.2.5/0.3.5. Here is a brief summary of what is included in the snapshots detailed bellow:

  • First, it doesn’t blow up in your face anymore, previous to this snapshot users of remoting and cluster might experiment errors because some parts of Kamon were not Serializable, making it imposible for them to use Kamon in such projects. Now we did what was necessary to ensure that all messages flow without problems, keep reading for more on that.

  • TraceContext propagation for regular messages: TraceContexts are propagated when sending a message to remote actors in the same way it works with local actors. This also covers messages sent via ActorSelection and routers with remote routees.

  • TraceContex propagation for system messages: If a actor with a remote supervisor fails, the TraceContext is also propagated through system messages to remote actors, meaning that if one of your actors fails in node A and the supervisor lives in node B, the TraceContext will still be there. This also covers the create actor scenario: if you deploy a new remote Actor while a TraceContext is available (e.g. using a actor per request, deploying in a remote node), the TraceContext available in the local node when deploying the remote actor will be available in the remote node when creating the actor instance.

  • A Trace can start in one node and finish in another: As simple as it sounds, start a TraceContext in one node, let it propagate thorugh messages to remote nodes and finish it over there! Sounds simple, but comes with a couple things you need to know about:

    • There is little protection from closing a TraceContext more than once. One of the biggest challenges of providing this support comes from the fact that we use the TraceContext to measure how long did a request/feature execution take to complete, which is an relatively easy task when eveything is local but challenging when working with distributed systems. For now we decided not to provide full protection against finishing a remote TraceContext more than once because the efforts of keeping a consistent view on the state of all TraceContexts across the cluster seems prohibitive performance wise. We might reconsider this in the future based on feedback. If you understand how the TraceContext works and how it is propagated you will be just fine, and if in doubt just drop us a line on the mailing list.
    • Even while all of our timing measurements are taken and reported in nanoseconds for local TraceContexts, when finishing a remote TraceContext the we can’t rely on the relative System.nanoTime and have to resort back to System.currentTimeMillis. Please make sure that you keep your clocks synchronized across the cluter.

We would like to receive as much feedback as possible from our users in order to take this in the right direction and provide a solid support on which you can rely for production monitoring. The snapshots are available in our snapshots repo and the published versions are:

  • 0.2.5-4b999c39b6bd09d891de718fad10b795264755c6, compatible with Akka 2.2, Spray 1.2, Play 2.2 and Scala 2.10.x
  • 0.3.5-23785a41dc3a0e9651ba87bc9dc255932ea64bd6, compatible with Akka 2.3, Spray 1.3, Play 2.3 and Scala 2.10.x
  • 0.3.5-fde062f7e700925e30b60f366ddcd66a04f7c2c5, compatible with Akka 2.3, Spray 1.3, Play 2.3 and Scala 2.11.x

Have fun with it!



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