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## Sample 650: Introduction to Priority Based Mediation

<definitions xmlns="http://ws.apache.org/ns/synapse"> <priorityExecutor name="exec"> <queues> <queue size="100" priority="1"/> <queue size="100" priority="10"/> </queues> </priorityExecutor> <proxy name="StockQuoteProxy"> <target> <inSequence> <filter source="$trp:priority" regex="1"> <then> <enqueue priority="1" sequence="priority_sequence" executor="exec"/> </then> <else> <enqueue priority="10" sequence="priority_sequence" executor="exec"/> </else> </filter> </inSequence> <outSequence> <send/> </outSequence> </target> <publishWSDL uri="file:repository/conf/sample/resources/proxy/sample_proxy_1.wsdl"/> </proxy> <sequence name="priority_sequence"> <log level="full"/> <send> <endpoint> <address uri="http://localhost:9000/services/SimpleStockQuoteService"/> </endpoint> </send> </sequence> </definitions>

### Objective

Demonstrate the usage of priority executors in Synapse to assign priority levels to requests and mediate them based on the assigned priority

### Pre-requisites

- Deploy the SimpleStockQuoteService in the sample Axis2 server and start Axis2
- Start Synapse using the configuration numbered 650 (repository/conf/sample/synapse_sample_650.xml)
  Unix/Linux: sh synapse.sh -sample 650
  Windows: synapse.bat -sample 650

### Executing the Client

Priority is applied only when synapse is loaded with enough messages to consume all of its core worker threads. So to observe the priority based mediation, it is required to use a load testing tool like JMeter, SOAP UI or Apache bench.

In this sample, client should send a HTTP header that specifies the priority of the message.This header name is 'priority'. This header is retrieved in the synapse configuration using the $trp:priority XPath expression. Then it is matched against the value 1. If it has the value 1, message is executed with priority 1. Otherwise the message is executed with priority 10.

Messages with different priorities are put into different priority queues. Then they are mediated in a manner so that high priority messages are always processed first.

Here are two sample SOAP requests that can be used to invoke the service using a tool like JMeter, or Apache Bench. For SOAP UI, user can use the WSDL repository/conf/sample/resources/proxy/sample_proxy_1.wsdl to create the request. The only difference between the two requests shown here is the symbol. One has the symbol as IBM and other has MSFT. For one type of requests set the priority header to 1 and for the next set the priority header to 10. Then load Synapse with a large volume of traffic consisting of both types of requests using the load testing tool. Back end Axis2 server prints the symbol of the incoming requests. User should be able to see more of the high priority symbol.

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"> <soapenv:Header xmlns:wsa="http://www.w3.org/2005/08/addressing"> <wsa:To>http://localhost:8281/services/SimpleStockQuoteService</wsa:To> <wsa:MessageID>urn:uuid:1B57D0B0BF770678DE1261165228620</wsa:MessageID> <wsa:Action>urn:getQuote</wsa:Action> </soapenv:Header> <soapenv:Body> <m0:getQuote xmlns:m0="http://services.samples"> <m0:request> <m0:symbol>IBM</m0:symbol> </m0:request> </m0:getQuote> </soapenv:Body> </soapenv:Envelope>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"> <soapenv:Header xmlns:wsa="http://www.w3.org/2005/08/addressing"> <wsa:To>http://localhost:8281/services/SimpleStockQuoteService</wsa:To> <wsa:MessageID>urn:uuid:1B57D0B0BF770678DE1261165228620</wsa:MessageID> <wsa:Action>urn:getQuote</wsa:Action> </soapenv:Header> <soapenv:Body> <m0:getQuote xmlns:m0="http://services.samples"> <m0:request> <m0:symbol>MSFT</m0:symbol> </m0:request> </m0:getQuote> </soapenv:Body> </soapenv:Envelope>

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