In this blog, I will explain the possible approach to take, extend the runtime statistics in the APIM to DAS. Custom event publishing is important when you want to publish a custom event which is not provided apim by default. Also, it will help to handle more advanced business requirements like message body based analytics which is also not proved by the APIM by default.

Class mediator[1] is another approach to extend the APIM runtime statistics as an event. You can create a java class with DAS data publisher which will publisher the event when Class mediator gets invoke. Here the sample java class for the class mediator. Before start implement makes sure to import all the required java dependencies to the project. For that please check the sample section for the source code.

package com.rukspot.sample.eventpublisher;

import org.apache.synapse.MessageContext;
import org.apache.synapse.mediators.AbstractMediator;
import org.apache.synapse.rest.RESTConstants;
import org.wso2.carbon.apimgt.gateway.APIMgtGatewayConstants;
import org.wso2.carbon.apimgt.gateway.handlers.security.APISecurityUtils;
import org.wso2.carbon.apimgt.gateway.handlers.security.AuthenticationContext;
import org.wso2.carbon.apimgt.impl.utils.APIUtil;
import org.wso2.carbon.databridge.agent.DataPublisher;

public class SimpleClassMediator extends AbstractMediator {


    public boolean mediate(MessageContext mc) {

        String context = (String) mc.getProperty(RESTConstants.REST_API_CONTEXT);
        String apiPublisher = (String) mc.getProperty(APIMgtGatewayConstants.API_PUBLISHER);
        String apiVersion = (String) mc.getProperty(RESTConstants.SYNAPSE_REST_API);
        String api = APIUtil.getAPINamefromRESTAPI(apiVersion);

        AuthenticationContext authContext = APISecurityUtils.getAuthenticationContext(mc);
        String username = "";
        String applicationName = "";
        if (authContext != null) {
            username = authContext.getUsername();
            applicationName = authContext.getApplicationName();
        }
        System.out.println(api);
        try {
            DataPublisher publisher = EventPublisher.getPublisher();
            String id = "org.wso2.apimgt.statistics.custom:1.0.0";
            Object[] payload= new Object[]{api,applicationName,username};
            publisher.publish(id, null, null, payload);
        } catch (Exception e) {
            System.out.println("error Sending event " + e.getMessage());
        }
        return true;
    }
}

Another way is to implement the data publisher in a synapse handler[2]. It is similar to the class mediator but it is implemented as a handler and place in the handler section in the API synapse. Here the sample handler class.

package com.rukspot.sample.eventpublisher;

import org.apache.synapse.MessageContext;
import org.apache.synapse.rest.AbstractHandler;
import org.apache.synapse.rest.RESTConstants;
import org.wso2.carbon.apimgt.gateway.APIMgtGatewayConstants;
import org.wso2.carbon.apimgt.gateway.handlers.security.APISecurityUtils;
import org.wso2.carbon.apimgt.gateway.handlers.security.AuthenticationContext;
import org.wso2.carbon.apimgt.impl.utils.APIUtil;
import org.wso2.carbon.databridge.agent.DataPublisher;

public class SimpleEventPublisherHandler extends AbstractHandler {
    public boolean handleRequest(MessageContext mc) {
        String context = (String) mc.getProperty(RESTConstants.REST_API_CONTEXT);
        String apiPublisher = (String) mc.getProperty(APIMgtGatewayConstants.API_PUBLISHER);
        String apiVersion = (String) mc.getProperty(RESTConstants.SYNAPSE_REST_API);
        String api = APIUtil.getAPINamefromRESTAPI(apiVersion);

        AuthenticationContext authContext = APISecurityUtils.getAuthenticationContext(mc);
        String username = "";
        String applicationName = "";
        if (authContext != null) {
            username = authContext.getUsername();
            applicationName = authContext.getApplicationName();
        }
        System.out.println(api);
        try {
            DataPublisher publisher = EventPublisher.getPublisher();
            String id = "org.wso2.apimgt.statistics.custom:1.0.0";
            Object[] payload= new Object[]{api,applicationName,username};
            publisher.publish(id, null, null, payload);
        } catch (Exception e) {
            System.out.println("error Sending event " + e.getMessage());
        }
        return true;
    }

    public boolean handleResponse(MessageContext messageContext) {
        return true;
    }
}

• Event mediator[3] is one of the ways to integrate to your mediation flow as a mediator. A mediator is a simple way to add a custom event stream without touching any java level codes.
• APIM 2.0.0 is not shipped with Event mediator by default. But it is possible to install feature in APIM 2.0.0 and configure.
• To install feature first add the relevant feature repository to the APIM according to this[4].
• Then find the PublishEvent Mediator Aggregate:4.6.1 feature and restart after done.
• To configure event publishing you need to configure the EventSink configuration and EventPublisher mediator.
• EventSink[5] configuration is to define the DAS connection-related information and sample configuration is as follow. The configuration is need to deploy in the /home/rukshan/apim/2.0.0/test/wso2am-2.0.0/repository/deployment/server/event-sinks/ directory with name testSink.xml

<?xml version="1.0" encoding="UTF-8"?>
<eventSink>
    <receiverUrl>tcp://localhost:7612</receiverUrl>
    <authenticatorUrl/>
    <username>admin</username>
    <password>admin</password>
</eventSink>

• Next, we need to define the event mediator in the Synapse API as follow.

<?xml version="1.0" encoding="UTF-8"?>
<api xmlns="http://ws.apache.org/ns/synapse"
     name="admin--sample"
     context="/sample/1.0.0"
     version="1.0.0"
     version-type="context">
   <resource methods="GET" url-mapping="/one" faultSequence="fault">
      <inSequence>
         <property name="api.ut.backendRequestTime"
                   expression="get-property('SYSTEM_TIME')"/>
         <filter source="$ctx:AM_KEY_TYPE" regex="PRODUCTION">
            <then>

        <publishEvent>
            <eventSink>testSink</eventSink>
            <streamName>test</streamName>
            <streamVersion>1.0.0</streamVersion>
            <attributes>
               <meta/>
               <correlation/>
               <payload>
                  <attribute name="atr1" type="STRING" defaultValue="" value="testValue"/>
                  <attribute name="atr2" type="STRING" defaultValue="" value="Test Region"/>
               </payload>
               <arbitrary/>
            </attributes>
         </publishEvent>

               <send>
                  <endpoint name="admin--sample_APIproductionEndpoint_0">
                     <http uri-template="http://localhost:8080/simple-service-webapp/webapi/myresource"/>
                     <property name="ENDPOINT_ADDRESS"
                               value="http://localhost:8080/simple-service-webapp/webapi/myresource"/>
                  </endpoint>
               </send>
            </then>
            <else>
               <sequence key="_sandbox_key_error_"/>
            </else>
         </filter>
      </inSequence>
      <outSequence>
         <class name="org.wso2.carbon.apimgt.usage.publisher.APIMgtResponseHandler"/>
         <send/>
      </outSequence>
   </resource>
   <resource methods="GET" url-mapping="/two" faultSequence="fault">
      <inSequence>
         <property name="api.ut.backendRequestTime"
                   expression="get-property('SYSTEM_TIME')"/>
         <filter source="$ctx:AM_KEY_TYPE" regex="PRODUCTION">
            <then>
               <send>
                  <endpoint name="admin--sample_APIproductionEndpoint_1">
                     <http uri-template="http://localhost:8080/simple-service-webapp/webapi/myresource"/>
                     <property name="ENDPOINT_ADDRESS"
                               value="http://localhost:8080/simple-service-webapp/webapi/myresource"/>
                  </endpoint>
               </send>
            </then>
            <else>
               <sequence key="_sandbox_key_error_"/>
            </else>
         </filter>
      </inSequence>
      <outSequence>
         <class name="org.wso2.carbon.apimgt.usage.publisher.APIMgtResponseHandler"/>
         <send/>
      </outSequence>
   </resource>
   <handlers>
      <handler class="org.wso2.carbon.apimgt.gateway.handlers.common.APIMgtLatencyStatsHandler"/>
      <handler class="org.wso2.carbon.apimgt.gateway.handlers.security.CORSRequestHandler">
         <property name="apiImplementationType" value="ENDPOINT"/>
      </handler>
      <handler class="org.wso2.carbon.apimgt.gateway.handlers.security.APIAuthenticationHandler"/>
      <handler class="org.wso2.carbon.apimgt.gateway.handlers.throttling.ThrottleHandler">
         <property name="productionMaxCount" value="2"/>
      </handler>
      <handler class="org.wso2.carbon.apimgt.usage.publisher.APIMgtUsageHandler"/>
      <handler class="org.wso2.carbon.apimgt.usage.publisher.APIMgtGoogleAnalyticsTrackingHandler">
         <property name="configKey" value="gov:/apimgt/statistics/ga-config.xml"/>
      </handler>
      <handler class="org.wso2.carbon.apimgt.gateway.handlers.ext.APIManagerExtensionHandler"/>
   </handlers>
</api>

• Bam mediator[6] is similar to the Event Mediator but it is now deprecated. But it will be useful if you are using an older version of APIM. An older version of APIM supports BAM mediator by default.
• To configure event publisher here also there is two component to configure. First, we need to define the bam server profile[7].In server profile, we define the connection setting as well as stream definition. Once you define these definitions we can directly refer them in the mediator to send the event

• To configure mediator, open your synapse API file and define the mediator in a proper place.

<bam xmlns="http://ws.apache.org/ns/synapse">
   <serverProfile name="test-bam-profile">
      <streamConfig name="org.wso2.apimgt.statistics.custom" version="1.0.0"></streamConfig>
   </serverProfile>
</bam>>

• And complete synapse file would be like this.

<?xml version="1.0" encoding="UTF-8"?>
<api xmlns="http://ws.apache.org/ns/synapse"
     name="admin--sample"
     context="/sample/1.0.0"
     version="1.0.0"
     version-type="context">
   <resource methods="GET" url-mapping="/*" faultSequence="fault">
      <inSequence>
         <filter source="$ctx:AM_KEY_TYPE" regex="PRODUCTION">
            <then>
               <property name="api.ut.backendRequestTime"
                         expression="get-property('SYSTEM_TIME')"/>

<bam xmlns="http://ws.apache.org/ns/synapse">
   <serverProfile name="test-bam-profile">
      <streamConfig name="org.wso2.apimgt.statistics.custom" version="1.0.0"></streamConfig>
   </serverProfile>
</bam>

               <send>
                  <endpoint name="admin--sample_APIproductionEndpoint_0">
                     <http uri-template="http://localhost:8080/simple-service-webapp/webapi/myresource"/>
                  </endpoint>
               </send>
            </then>
            <else>
               <sequence key="_sandbox_key_error_"/>
            </else>
         </filter>
      </inSequence>
      <outSequence>
         <class name="org.wso2.carbon.apimgt.usage.publisher.APIMgtResponseHandler"/>
         <send/>
      </outSequence>
   </resource>
   <handlers>
      <handler class="org.wso2.carbon.apimgt.gateway.handlers.security.CORSRequestHandler">
         <property name="apiImplementationType" value="ENDPOINT"/>
      </handler>
      <handler class="org.wso2.carbon.apimgt.gateway.handlers.security.APIAuthenticationHandler"/>
      <handler class="org.wso2.carbon.apimgt.gateway.handlers.throttling.APIThrottleHandler">
         <property name="id" value="A"/>
         <property name="policyKeyResource"
                   value="gov:/apimgt/applicationdata/res-tiers.xml"/>
         <property name="policyKey" value="gov:/apimgt/applicationdata/tiers.xml"/>
         <property name="policyKeyApplication"
                   value="gov:/apimgt/applicationdata/app-tiers.xml"/>
      </handler>
      <handler class="org.wso2.carbon.apimgt.usage.publisher.APIMgtUsageHandler"/>
      <handler class="org.wso2.carbon.apimgt.usage.publisher.APIMgtGoogleAnalyticsTrackingHandler">
         <property name="configKey" value="gov:/apimgt/statistics/ga-config.xml"/>
      </handler>
      <handler class="org.wso2.carbon.apimgt.gateway.handlers.ext.APIManagerExtensionHandler"/>
   </handlers>
</api>

Here you can find the above-mentioned sample. Class mediator and Handler implementation can be found on the jar inside the zip. Download the sample from here. Please find the readme for more about the configuration.

1. https://docs.wso2.com/display/ESB490/Class+Mediator
2. https://docs.wso2.com/display/ESB490/Writing+a+Synapse+Handler
3. https://docs.wso2.com/display/ESB490/Publish+Event+Mediator
4. https://docs.wso2.com/display/ADMIN44x/Installing+Features+via+the+UI
5. https://docs.wso2.com/display/ESB490/Working+with+Event+Sinks
6. https://docs.wso2.com/display/ESB481/BAM+Mediator
7. https://docs.wso2.com/display/ESB481/Configuring+a+Server+Profile