What are the best use cases for Akka framework

Question

I have heard lots of raving about Akka framework  Java Scala service platform   but so far have not seen many actual examples of use cases it would be good for  So I would be interested in hearing about things developers have used it succesfully   Only one limitation  please do not include case of writing a chat server    why  since this has been overused as an example for lots of similar things

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We use Akka in several projects at work  the most interesting of which is related to vehicle crash repair   Primarily in the UK but now expanding to the US  Asia  Australasia and Europe  We use actors to ensure that crash repair information is provided realtime to enable the safe and cost effective repair of vehicles   The question with Akka is really more  what can t you do with Akka    Its ability to integrate with powerful frameworks  its powerful abstraction and all of the fault tolerance aspects make it a very comprehensive toolkit

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You can use Akka for several different kinds of things   I was working on a website  where I migrated the technology stack to Scala and Akka  We used it for pretty much everything that happened on the website  Even though you might think a Chat example is bad  all are basically the same    Live updates on the website  e g  views  likes       Showing live user comments Notification services Search and all other kinds of services   Especially the live updates are easy since they boil down to what a Chat example ist  The services part is another interesting topic because you can simply choose to use remote actors and even if your app is not clustered  you can deploy it to different machines with ease   I am also using Akka for a PCB autorouter application with the idea of being able to scale from a laptop to a data center  The more power you give it  the better the result will be  This is extremely hard to implement if you try to use usual concurrency because Akka gives you also location transparency   Currently as a free time project  I am building a web framework using only actors  Again the benefits are scalability from a single machine to an entire cluster of machines  Besides  using a message driven approach makes your software service oriented from the start  You have all those nice components  talking to each other but not necessarily knowing each other  living on the same machine  not even in the same data center   And since Google Reader shut down I started with a RSS reader  using Akka of course  It is all about encapsulated services for me  As a conclusion  The actor model itself is what you should adopt first and Akka is a very reliable framework helping you to implement it with a lot of benefits you will receive along the way

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An example of how we use it would be on a priority queue of debit credit card transactions  We have millions of these and the effort of the work depends on the input string type  If the transaction is of type CHECK we have very little processing but if it is a point of sale then there is lots to do such as merge with meta data  category  label  tags  etc  and provide services  email sms alerts  fraud detection  low funds balance  etc    Based on the input type we compose classes of various traits  called mixins  necessary to handle the job and then perform the work  All of these jobs come into the same queue in realtime mode from different financial institutions  Once the data is cleansed it is sent to different data stores for persistence  analytics  or pushed to a socket connection  or to Lift comet actor  Working actors are constantly self load balancing the work so that we can process the data as fast as possible  We can also snap in additional services  persistence models  and stm for critical decision points    The Erlang OTP style message passing on the JVM makes a great system for developing realtime systems on the shoulders of existing libraries and application servers    Akka allows you to do message passing like you would in a traditional esb but with speed  It also gives you tools in the framework to manage the vast amount of actor pools  remote nodes  and fault tolerance that you need for your solution

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We use Akka in spoken dialog systems  primetalk   Both internally and externally  In order to simultaneously run a lot of telephony channels on a single cluster node it is obviously necessary to have some multithreading framework  Akka works just perfect  We have previous nightmare with the java-concurrency  And with Akka it is just like a swing     it simply works  Robust and reliable  24 7  non-stop   Inside a channel we have real-time stream of events that are processed in parallel  In particular  - lengthy automatic speech recognition     is done with an actor  - audio output producer that mixes a few audio sources  including synthesized speech   - text-to-speech conversion is a separate set of actors shared between channels  - semantic and knowledge processing   To make interconnections of complex signal processing we use SynapseGrid  It has the benefit of compile-time checking of the DataFlow in the complex actor systems

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We are using Akka in a large scale Telco project  unfortunately I can t disclose a lot of details   Akka actors are deployed and accessed remotely by a web application  In this way  we have a simplified RPC model based on Google protobuffer and we achieve parallelism using Akka Futures  So far  this model has worked brilliantly  One note  we are using the Java API

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If you abstract the chat server up a level  then you get the answer   Akka provides a messaging system that is akin to Erlang s  let it crash  mentality   So examples are things that need varying levels of durability and reliability of messaging    Chat server Network layer for an MMO Financial data pump Notification system for an iPhone mobile whatever app REST Server Maybe something akin to WebMachine  guess    The nice things about Akka are the choices it affords for persistence  it s STM implementation  REST server and fault-tolerance   Don t get annoyed by the example of a chat server  think of it as an example of a certain class of solution   With all their excellent documentation  I feel like a gap is this exact question  use-cases and examples   Keeping in mind the examples are non-trivial     Written with only experience of watching videos and playing with the source  I have implemented nothing using akka

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We are using akka with its camel plugin to distribute our analysis and trending processing for twimpact com  We have to process between 50 and 1000 messages per second  In addition to multi-node processing with camel it is also used to distribute work on a single processor to multiple workers for maximum performance  Works quite well  but requires some understanding of how to handle congestions

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We use Akka to process REST calls asynchronously - together with async web server  Netty-based  we can achieve 10 fold improvement on the number of users served per node server  comparing to traditional thread per user request model   Tell it to your boss that your AWS hosting bill is going to drop by the factor of 10 and it is a no-brainer  Shh    dont tell it to Amazon though

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I was trying out my hands on Akka  Java api   What I tried was to compare Akka s actor based concurrency model with that of plain Java concurrency model  java util concurrent classes    The use case was a simple canonical map reduce implementation of character count  The dataset was a collection of randomly generated strings  400 chars in length   and calculate the number of vowels in them   For Akka I used a BalancedDispatcher for load balancing amongst threads  and RoundRobinRouter  to keep a limit on my function actors   For Java  I used simple fork join technique  implemented without any work stealing algorithm  that would fork map reduce executions and join the results  Intermediate results were held in blocking queues to make even the joining as parallel as possible  Probably  if I am not wrong  that would mimic somehow the  mailbox  concept of Akka actors  where they receive messages   Observation  Till medium loads   50000 string input  the results were comparable  varying slightly in different iterations  However  as I increased my load to  100000 it would hang the Java solution  I configured the Java solution with 20-30 threads under this condition and it failed in all iterations    Increasing the load to 1000000  was fatal for Akka as well  I can share the code with anyone interested to have a cross check   So for me  it seems Akka scales out better than traditional Java multithreaded solution  And probably the reason is the under the hood magic of Scala   If I can model a problem domain as an event driven message passing one  I think Akka is a good choice for the JVM    Test performed on  Java version 1 6 IDE  Eclipse 3 7 Windows Vista 32 bit  3GB ram  Intel Core i5 processor  2 5 GHz clock speed  Please note  the problem domain used for the test can be debated and I tried to be as much fair as my Java knowledge allowed  -

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Disclaimer  I am the PO for Akka  Besides offering a concurrency smorgasbord that is much simpler to reason about and to get correct  actors  agents  dataflow concurrency  and with concurrency control in the form of STM   Here are some use-cases you might consider    Transaction processing  online gaming  finance  statistics  betting  social media  telecom        scale up  scale out  fault-tolerance   HA  Service backend  any industry  any app   service REST  SOAP  cometd etc act as message hub   integration layer scale up  scale out  fault-tolerance   HA  Snap-in concurrency parallelism   any app    Correct Simple to work with and understand Just add the jars to your existing JVM project  use Scala  Java  Groovy or JRuby   Batch processing   any industry    Camel integration to hook up with batch data sources Actors divide and conquer the batch workloads  Communications hub   telecom  web media  mobile media    scale up  scale out  fault-tolerance   HA  Game server  online gaming  betting   scale up  scale out  fault-tolerance   HA  BI datamining general purpose crunching  scale up  scale out  fault-tolerance   HA  insert other nice use cases here

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I have used it so far in two real projects very successfully  both are in the near real-time traffic information field  traffic as in cars on highways   distributed over several nodes  integrating messages between several parties  reliable backend systems  I m not at liberty to give specifics on clients yet  when I do get the OK maybe it can be added as a reference    Akka has really pulled through on those projects  even though we started when it was on version 0 7   we are using scala by the way   One of the big advantages is the ease at which you can compose a system out of actors and messages with almost no boilerplating  it scales extremely well without all the complexities of hand-rolled threading and you get asynchronous message passing between objects almost for free   It is very good in modeling any type of asynchronous message handling  I would prefer to write any type of  web  services system in this style than any other style   Have you ever tried to write an asynchronous web service  server side  with JAX-WS  that s a lot of plumbing   So I would say any system that does not want to hang on one of its components because everything is implicitly called using synchronous methods  and that one component is locking on something  It is very stable and the let-it-crash   supervisor solution to failure really works well  Everything is easy to setup programmatically and not hard to unit test   Then there are the excellent add-on modules  The Camel module really plugs in well into Akka and enables such easy development of asynchronous services with configurable endpoints    I m very happy with the framework and it is becoming a defacto standard for the connected systems that we build

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I ve recently implemented the canonical map-reduce example in Akka  Word count  So it s one use case of Akka  better performance  It was more of a experiment of JRuby and Akka s actors than anything else  but it also shows that Akka is not Scala or Java only  it works on all languages on top of JVM

[java] What are the best use cases for Akka framework

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