http://ayende.comAyende @ RahienCopyright (C) Ayende Rahien 2004 - 2021 (c) 202660I thought this scenario is ideal to be integrated with RhinoESB and messaging... http://ayende.com/4824/raven-situational-awareness#comment14http://ayende.com/4824/raven-situational-awareness#comment14Thu, 28 Apr 2011 06:23:56 GMTDaniel, Discovery & heartbeat have nothing to do with Rhino ESB http://ayende.com/4824/raven-situational-awareness#comment13http://ayende.com/4824/raven-situational-awareness#comment13Thu, 28 Apr 2011 05:25:53 GMTHy ayende Why are you using Udp with wcf. Isn't that scenario a typical one for rhino esb? Discovery, heartbeat etc. this all screams RhinoEsb ;) Daniel http://ayende.com/4824/raven-situational-awareness#comment12http://ayende.com/4824/raven-situational-awareness#comment12Thu, 28 Apr 2011 05:25:13 GMTHi Ayende, could you share with us how you tested it? I find it very interesting. http://ayende.com/4824/raven-situational-awareness#comment11http://ayende.com/4824/raven-situational-awareness#comment11Wed, 27 Apr 2011 17:45:26 GMTGoogle uses Paxos in its BigTable implementation. I came across this not by wikipedia, but in reading the BigTable pub. Pretty interesting http://ayende.com/4824/raven-situational-awareness#comment10http://ayende.com/4824/raven-situational-awareness#comment10Wed, 27 Apr 2011 15:14:47 GMT@hangy This is a standard trick. You cannot copyright common words but you can copyright misspelled ones :) http://ayende.com/4824/raven-situational-awareness#comment9http://ayende.com/4824/raven-situational-awareness#comment9Wed, 27 Apr 2011 13:20:05 GMTI know it's a breaking change, but you have a typo in the namespace and the the project files: Raven.SituationaAwareness misses an "l". http://ayende.com/4824/raven-situational-awareness#comment8http://ayende.com/4824/raven-situational-awareness#comment8Wed, 27 Apr 2011 12:23:25 GMTI cannot find anything concrete that is wrong with the code so it was probably a false alarm. http://ayende.com/4824/raven-situational-awareness#comment7http://ayende.com/4824/raven-situational-awareness#comment7Wed, 27 Apr 2011 10:58:31 GMTtopologyState is ConcurrentDictionary http://ayende.com/4824/raven-situational-awareness#comment6http://ayende.com/4824/raven-situational-awareness#comment6Wed, 27 Apr 2011 10:27:03 GMTIs topologyState accessed thread-safely? Is is being accessed and modified in the callback concurrently. I must say that I did not completely digest the code but this "smelled" of threading-bug. http://ayende.com/4824/raven-situational-awareness#comment5http://ayende.com/4824/raven-situational-awareness#comment5Wed, 27 Apr 2011 10:21:53 GMTTobi, Where is the bug? Are you talking about the usage of the Timer in there? There is no bug here, we might be running concurrently, but the code is safe for multi threading access. http://ayende.com/4824/raven-situational-awareness#comment4http://ayende.com/4824/raven-situational-awareness#comment4Wed, 27 Apr 2011 10:12:50 GMTThere is a threading bug here: The timer can fire on multiple threads at the same time (for example if your callback takes over 3 seconds to run). Your callback must be thread safe, probably by just ignoring concurrent timer events. Also after disposing the timer, events will still be delivered potentially infinitely many times because they might have queued up on the thread pool. I ran into this once and solved it with the following timer wrapper class which I license to you without restrictions: public class StoppableSequentialTimer : IDisposable { readonly Action callback; readonly System.Threading.Timer timer; bool disposed; bool running; public StoppableSequentialTimer(Action callback, TimeSpan dueTime, TimeSpan intervall) { if (callback == null) throw new ArgumentNullException("callback"); this.callback = callback; timer = new System.Threading.Timer(_ => TimerCallback(), null, dueTime, intervall); } void TimerCallback() { lock (timer) { if (disposed || running) return; running = true; } try { callback(); } finally { lock (timer) running = false; } } public void Dispose() { lock (timer) disposed = true; timer.Dispose(); } } The callback executes non-concurrently and stops firing once the Timer is disposed. After disposal only a single superfluous callback run can happen. http://ayende.com/4824/raven-situational-awareness#comment3http://ayende.com/4824/raven-situational-awareness#comment3Wed, 27 Apr 2011 10:04:27 GMTRoja, Nodes will be notified about the split and about the joining, masters will be assigned for each split, and when the split it merged, will be merged as well. What they do about it is outside the scope of RSA and in the realm of the actual server running it Paxos is implemented internally, solely for the purpose of master detection http://ayende.com/4824/raven-situational-awareness#comment2http://ayende.com/4824/raven-situational-awareness#comment2Wed, 27 Apr 2011 09:49:34 GMTHow is the split-brain ( [http://en.wikipedia.org/wiki/Split-brain_](http://en.wikipedia.org/wiki/Split-brain_)(Computing) ) problem dealt with by Raven.SituationalAwareness? Is the implementation of Paxos protocol internal to the framework or is it based on an external dependency? http://ayende.com/4824/raven-situational-awareness#comment1http://ayende.com/4824/raven-situational-awareness#comment1Wed, 27 Apr 2011 09:44:31 GMT