Hi, Here is an alternative approach for service discovery with out using Zookeeper and has better synergy with AKKA clustering; Consul[0].
Consul is based on the Raft protocol[1] for consensus. But Consul also makes uses of Serf’s[2] gossip protocol for LAN and WAN membership status and leader election. Like etcd and others, Consul's features include service discovery and a similar key-value store, but also provides health checking functionality and the ability to span multiple data-centers out-of-the-box. The multiple data-center support comes from Consul's use of its eventually consistent gossip protocol. I find this first class support for multiple datacenters to be an interesting leap ahead of other solutions that leave it up to the implementer to figure out. Perhaps the integration can best be achieved with an akka extension that acts as a client to Consul potentially leveraging either the HTTP API [3] or the roc protocol [4]. With this I believe you could address the different consistency levels expressed (CP + AP) by all participants in this thread so far. In addition, it can scale to support the situations Brian has described. If nothing else I think it at least provides some good ideas for service discovery. Regards, Todd [0] http://www.consul.io/ [1] https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf [2] http://www.serfdom.io/ [3] http://www.consul.io/docs/agent/http.html [4] http://www.consul.io/docs/agent/rpc.html On Monday, June 2, 2014 11:51:06 AM UTC-4, Evan Chan wrote: > > Hey guys, > > I would like to run an idea by the fine Akka community - which is to > discuss what it would take to turn Akka into a platform for building a > network of "microservices": each one independently redeployable and easy to > change, yet through a common platform, take advantage of the distributed > supervision, messaging and other goodies from Akka. > > Here are some characteristics of such a platform: > > > - > > Service discovery > - > > Supporting different kinds of data flow topologies - request response, > as well as streaming data; pub-sub, etc. > - > > Provide common abstractions for efficient data serialization > - > > Support backpressure and flow control, to rate limit requests > - > > Support easy scaling of each component, including routing of messages > or requests to multiple instances > - > > Enable easy testing of multiple services (for example, see Akka’s > sbt-multi-jvm plugin) > - > > A common platform for application metrics > - > > Distributed message or request tracing, to help with visibility and > debugging > - > > Support polyglot development - it should be possible to develop > services in different languages > > > I think many of these are already provided by Akka, but I wanted to run > through each one in more detail: > > *Service Discovery* > Right now every actor talks to another actor location-transparently; > however, when looking up an external ActorRef, one does have to know the > mechanism, ie is it looking up in cluster, or remote, etc.... is it > another actorsystem etc... (this could have changed in 2.2 and 2.3, but > I'm not up to date :-p) What I'm looking for is a > mechanism-independent way of looking up actors, remote or not. IE, I > should just need to do this: > > val downstreamActorRef = System.lookupByName(service = "tradingSystem", > actor = "masterTrader", ....) > > Under the hood this looks up the actorRef using one of configurable > mechanisms: > - Akka Cluster is certainly one way to go, with nodes > - At work we use Zookeeper and Curator. It would be great to make this > platform support multiple discovery types > > *Data Flow Topology* > - Akka is pretty good at this already, supporting many types of data > flow. The only concern I see is that you have to define the flow via the > like of routers and such, which are defined in the code on each node, > rather than externally via say a message queue (see ZMQ, NSQ etc). This > can be mitigated through DI and configuration and things like that, of > course. > > *Data Serialization* > If we are using native Akka protocol to talk over the wire, this is > already really good. One defines case classes, and Akka transparently > serializes them over the network if the actor is remote. This is one thing > about Akka that really appeals to me. > > So the question is can we make this work for Play / Akka HTTP > transparently as well? > > *Related - Polyglot support* > How would a Ruby/Python/etc process talk to an Akka network? My thoughts: > - Easiest way would be to have a way to automagically generate HTTP > endpoints that includes case class serialization to/from JSON. Type > classes to handle special data types. > - Did you guys define the Akka binary protocol and keep it stable? > Client libraries could then be written for different langauges, but this > doesn't solve the problem of message format -- Java serialization and > Chill/Kryo won't work. > > *Backpressure and Flow Control* > Reactive streams looks really promising here. How it ties into routing, > topologies, etc. I'd like to find out more about. > Also, reactive streams won't work for request/response protocols. > > *Application Metrics and Tracing* > Microservices means it becomes more and more important to figure out > what's going on across many services. Fortunately there's a lot of work > in this area; multiple third party libs to provide automatic metrics; > somebody wrote an Akka integration with Twitter's Dapper-like tracing > system, and I have written a tracing/graphing system as well. > > *Hot Reloads* > I didn't include this in the list above, because the assumption is that > with lots of independent small services, they will be naturally easier to > redeploy. Some will argue that the JVM is heavyweight (actually I think a > lightly loaded JVM app is under 50MB, which is very reasonable), and will > want Erlang-style hot reloads of individual actors. This is really tricky > area though. > > Anyways, I'd love to get the thoughts of the community about this idea of > using Akka as a "microservice" platform. > > Thanks! > Evan > > > -- >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>> Check the FAQ: >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user --- You received this message because you are subscribed to the Google Groups "Akka User List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/akka-user. For more options, visit https://groups.google.com/d/optout.
