Akka Java Cluster Example with SBR

Akka Split Brain Resolver (SBR)

This project provides an example of running an Akka cluster with SBR enabled. The example code uses cluster sharding to run a collection of actors across an Akka cluster.

To see an example of SBR in action, follow the steps below to start up a cluster of 2 or more nodes. Once the cluster is up and running stop one of the nodes by killing the node JVM. On Linux systems or a Mac use the kill -9 <PID> command to terminate one of the cluster node JVMs.

With SBR, when one or more nodes abruptly leaves a cluster the remaining cluster nodes will down the unreachable node or nodes. SBR logs node downing events in the log file of the cluster leader node. Search the leader log file for the term "SBR".

See the SBR documentation for information on the mechanics of SBR and instructions for enabling it.

Installation and Running

git clone https://github.com/mckeeh3/akka-java-cluster-sharding.git
cd akka-java-cluster-sharding
mvn compile

The following Maven command runs a signle JVM with 3 Akka actor systems on ports 2551, 2552, and a radmonly selected port.

mvn exec:java

To run on specific ports use the following -D option for passing in command line arguements.

mvn exec:java -Dexec.args="2551"

The default no arguments is equilevalant to the following.

mvn exec:java -Dexec.args="2551 2552 0"

A common way to run tests is to start single JVMs in multiple command windows. This simulates running a multi-node Akka cluster. For example, run the following 4 commands in 4 command windows.

mvn exec:java -Dexec.args="2551" > /tmp/$(basename $PWD)-1.log

mvn exec:java -Dexec.args="2552" > /tmp/$(basename $PWD)-2.log

mvn exec:java -Dexec.args="0" > /tmp/$(basename $PWD)-3.log

mvn exec:java -Dexec.args="0" > /tmp/$(basename $PWD)-4.log

This runs a 4 node Akka cluster starting 2 nodes on ports 2551 and 2552, which are the cluster seed nodes as configured and the application.conf file. And 2 nodes on randomly selected port numbers. The optional redirect > /tmp/$(basename $PWD)-4.log is an example for pushing the log output to filenames based on the project direcctory name.

For convenience, in a Linux command shell define the following aliases.

alias p1='cd ~/akka-java/akka-java-cluster'
alias p2='cd ~/akka-java/akka-java-cluster-aware'
alias p3='cd ~/akka-java/akka-java-cluster-singleton'
alias p4='cd ~/akka-java/akka-java-cluster-sharding'
alias p5='cd ~/akka-java/akka-java-cluster-persistence'
alias p6='cd ~/akka-java/akka-java-cluster-persistence-query'

alias m1='clear ; mvn exec:java -Dexec.args="2551" > /tmp/$(basename $PWD)-1.log'
alias m2='clear ; mvn exec:java -Dexec.args="2552" > /tmp/$(basename $PWD)-2.log'
alias m3='clear ; mvn exec:java -Dexec.args="0" > /tmp/$(basename $PWD)-3.log'
alias m4='clear ; mvn exec:java -Dexec.args="0" > /tmp/$(basename $PWD)-4.log'

The p1-6 alias commands are shortcuts for cd'ing into one of the six project directories. The m1-4 alias commands start and Akka node with the appropriate port. Stdout is also redirected to the /tmp directory.

Description

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