Writing a load balance algorithm for WSO2 ESB - algorithm

Question

I'm facing up to the load balance algorithm implementation for customizing the load balance endpoint.
On this documentation page:
http://docs.wso2.org/display/ESB470/Load-balance+Endpoint
I read:
Algorithm - Either a default "Round-robin" or custom loaded algorithm of the group. See more information about this algorithm in the article.
Where "article" is a link point to this page:
http://supunk.blogspot.it/2010/02/writing-load-balance-algorithm-for-wso2.html
But the referred article is not complete and doesn't tell anything about the algorithm development. Could anyone give me a valid example?

Answer 1

You can use below sample to send multiple request to share between diffent endpoint using RoundRobin algo.
<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
name="TestLoadBalance"
transports="https,http"
statistics="disable"
trace="disable"
startOnLoad="true">
<target>
<endpoint>
<loadbalance algorithm="org.apache.synapse.endpoints.algorithms.RoundRobin">
<endpoint>
<address uri="http://localhost:9000/services/SimpleStockQuoteService/"/>
</endpoint>
<endpoint>
<address uri="http://localhost:9001/services/SimpleStockQuoteService/"/>
</endpoint>
<endpoint>
<address uri="http://localhost:9002/services/SimpleStockQuoteService/"/>
</endpoint>
</loadbalance>
</endpoint>
</target>
<description/>
</proxy>

Answer 2

As the documentation specifies, the algorithm should be an implementation of org.apache.synapse.endpoints.algorithms.LoadbalanceAlgorithm
You need to write a class implementing LoadbalanceAlgorithm interface. You can refer the existing implementations RoundRobin, WeightedRRLCAlgorithm and WeightedRoundRobin classes found in org.apache.synapse.endpoints.algorithms package.
Then create a jar file with your class and add it to <ESB_HOME>/repository/components/lib folder and restart the server.
Now when adding a Load Balance Endpoint, select Other... for the Algorithm and provide the full classname of your custom algorithm. For example: org.apache.synapse.endpoints.algorithms.WeightedRoundRobin

Answer 3

Looking at
LoadBalanceAlgortihm it's not possibile to simply give it a dynamic list of endpoint.
Concerning LoadBalanceMambershipHandler and its implementation (Axis2 and Service)...it uses object like:
org.apache.axis2.clustering.management.GroupManagementAgent
and
org.apache.axis2.clustering.ClusteringAgent
so you have to configure your nodes in cluster using the axi2.xml inside /repository/conf/axis2 folder of your ESB.
Use the ESB registry to save the loadbalance enpoint in and then access it by code for adding it a new list of address endpoint.