9bc01ae265
The idea is to filter the sources, replacing @<var>@ occurrences with the mapping for <var> (which is currently hard-coded). @@ -> @. In order to make this work, I had to move the doc sources one directory down (into akka-docs/rst) so that the filtered result could be in a sibling directory so that relative links (to _sphinx plugins or real code) would continue to work. While I was at it I also changed it so that WARNINGs and ERRORs are not swallowed into the debug dump anymore but printed at [warn] level (minimum). One piece of fallout is that the (online) html build is now run after the normal one, not in parallel.
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ReStructuredText
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.. _howto-scala:
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######################
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HowTo: Common Patterns
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######################
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This section lists common actor patterns which have been found to be useful,
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elegant or instructive. Anything is welcome, example topics being message
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routing strategies, supervision patterns, restart handling, etc. As a special
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bonus, additions to this section are marked with the contributor’s name, and it
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would be nice if every Akka user who finds a recurring pattern in his or her
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code could share it for the profit of all. Where applicable it might also make
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sense to add to the ``akka.pattern`` package for creating an `OTP-like library
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<http://www.erlang.org/doc/man_index.html>`_.
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Throttling Messages
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===================
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Contributed by: Kaspar Fischer
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"A message throttler that ensures that messages are not sent out at too high a rate."
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The pattern is described in `Throttling Messages in Akka 2 <http://letitcrash.com/post/28901663062/throttling-messages-in-akka-2>`_.
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Balancing Workload Across Nodes
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===============================
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Contributed by: Derek Wyatt
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"Often times, people want the functionality of the BalancingDispatcher with the
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stipulation that the Actors doing the work have distinct Mailboxes on remote
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nodes. In this post we’ll explore the implementation of such a concept."
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The pattern is described `Balancing Workload across Nodes with Akka 2 <http://letitcrash.com/post/29044669086/balancing-workload-across-nodes-with-akka-2>`_.
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Ordered Termination
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===================
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Contributed by: Derek Wyatt
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"When an Actor stops, its children stop in an undefined order. Child termination is
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asynchronous and thus non-deterministic.
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If an Actor has children that have order dependencies, then you might need to ensure
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a particular shutdown order of those children so that their postStop() methods get
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called in the right order."
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The pattern is described `An Akka 2 Terminator <http://letitcrash.com/post/29773618510/an-akka-2-terminator>`_.
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Akka AMQP Proxies
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=================
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Contributed by: Fabrice Drouin
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"“AMQP proxies” is a simple way of integrating AMQP with Akka to distribute jobs across a network of computing nodes.
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You still write “local” code, have very little to configure, and end up with a distributed, elastic,
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fault-tolerant grid where computing nodes can be written in nearly every programming language."
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The pattern is described `Akka AMQP Proxies <http://letitcrash.com/post/29988753572/akka-amqp-proxies>`_.
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Shutdown Patterns in Akka 2
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===========================
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Contributed by: Derek Wyatt
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“How do you tell Akka to shut down the ActorSystem when everything’s finished?
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It turns out that there’s no magical flag for this, no configuration setting, no special callback you can register for,
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and neither will the illustrious shutdown fairy grace your application with her glorious presence at that perfect moment.
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She’s just plain mean.
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In this post, we’ll discuss why this is the case and provide you with a simple option for shutting down “at the right time”,
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as well as a not-so-simple-option for doing the exact same thing."
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The pattern is described `Shutdown Patterns in Akka 2 <http://letitcrash.com/post/30165507578/shutdown-patterns-in-akka-2>`_.
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Distributed (in-memory) graph processing with Akka
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==================================================
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Contributed by: Adelbert Chang
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"Graphs have always been an interesting structure to study in both mathematics and computer science (among other fields),
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and have become even more interesting in the context of online social networks such as Facebook and Twitter,
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whose underlying network structures are nicely represented by graphs."
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The pattern is described `Distributed In-Memory Graph Processing with Akka <http://letitcrash.com/post/30257014291/distributed-in-memory-graph-processing-with-akka>`_.
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Case Study: An Auto-Updating Cache Using Actors
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===============================================
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Contributed by: Eric Pederson
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"We recently needed to build a caching system in front of a slow backend system with the following requirements:
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The data in the backend system is constantly being updated so the caches need to be updated every N minutes.
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Requests to the backend system need to be throttled.
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The caching system we built used Akka actors and Scala’s support for functions as first class objects."
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The pattern is described `Case Study: An Auto-Updating Cache using Actors <http://letitcrash.com/post/30509298968/case-study-an-auto-updating-cache-using-actors>`_.
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Discovering message flows in actor systems with the Spider Pattern
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==================================================================
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Contributed by: Raymond Roestenburg
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"Building actor systems is fun but debugging them can be difficult, you mostly end up browsing through many log files
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on several machines to find out what’s going on. I’m sure you have browsed through logs and thought,
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“Hey, where did that message go?”, “Why did this message cause that effect” or “Why did this actor never get a message?”
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This is where the Spider pattern comes in."
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The pattern is described `Discovering Message Flows in Actor System with the Spider Pattern <http://letitcrash.com/post/30585282971/discovering-message-flows-in-actor-systems-with-the>`_.
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Template Pattern
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================
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*Contributed by: N. N.*
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This is an especially nice pattern, since it does even come with some empty example code:
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.. includecode:: code/docs/pattern/ScalaTemplate.scala
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:include: all-of-it
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:exclude: uninteresting-stuff
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.. note::
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Spread the word: this is the easiest way to get famous!
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Please keep this pattern at the end of this file.
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