Message mediation mode is one of the operational modes of WSO2 ESB where ESB functions as an intermediate message router. When operating in this mode, it can filter, transform, drop or forward messages to an endpoint based on the given parameters. A unit of the mediation flow is a mediator. Sequences define the message mediation behavior of the ESB. A sequence is a series of mediators, where each mediator is a unit entity that can input a message, carry out a predefined processing task on the message, and output the message for further processing.
What is debugging with respect to mediation
Debugging is where you want to know if these units, which function as separate entities are operating as intended, or if a combination of these units are operating as a whole as intended. WSO2 ESB packs the ESB Mediation debugger that enables you to debug the ESB message mediation flow in the server. Tooling support for the ESB Mediation debugger is provided by the WSO2 ESB Tooling Plugin.
Creating the ESB artifact
Follow the steps below to create a sample ESB artifact, to which you apply mediation.
- Install the WSO2 ESB Tooling Plugin and run it. For instructions, see Installing WSO2 ESB Tooling.
- Create the ESB artifact using the WSO2 ESB Tooling Plugin. For instructions, see Working with ESB Artifacts.
- Deploy the artifact you created on WSO2 ESB. For instructions, go to Deploying the ESB Config project.
Enabling mediation debugging
Follow the steps below to enable debugging with respect to mediation.
- Click Run in the top menu of the WSO2 ESB Tooling Plugin, and then click Debug Configurations.
- Double click ESB Mediation Debugger as shown below.
- Enter the details to create a new configuration as shown in the example below. You need to define two port numbers and a hostname t o connect the ESB server with the WSO2 ESB Tooling Plugin in the mediation debug mode.
- Execute the following command to s tart WSO2 ESB server in the debug mode by passing a system variable at start up:
sh wso2server.sh -Desb.debug=true
Click Debug in the WSO2 ESB Tooling Plugin when the WSO2 ESB Console indicates the following.
You have approximately a one-minute time span to connect the WSO2 ESB Tooling Plugin with the ESB server for the execution of the above created debug configuration. Otherwise, the ESB server will stop listening and start without connecting with the debugger tool.
In the WSO2 ESB Tooling Plugin, right click and add breakpoints or skip points on the desired mediators to start debugging as shown in the example below.
You can add the following debugging options on the mediators using the right click context menu.
- Toggle Breakpoint: Adds a breakpoint to the selected mediator
- Toggle Skip Point: Adds a skip point to the selected mediator
- Resend ESB Debug Points: If you re-start the ESB server, or if you re-deploy the proxy service after changing its Synapse configuration, you need to re-send the information on breakpoints to the WSO2 ESB server. This re-sends all registered debugging points to the ESB Server.
- Delete All ESB Debug Points: Deletes all registered debug points from the ESB Server and the WSO2 ESB Tooling Plugin
Information provided by the Debugger Tool
When your target artifact gets a request message and when the mediation flow reaches a mediator marked as a breakpoint, the message mediation process suspends at that point. A tool tip message of the suspended mediator displays the message envelope of the message payload at that point as shown in the example below.
You can view the message payload at that point of the message flow also in the Message Envelope tab as shown below.
Also, you can view the message mediation properties in the Variables view as shown in the example below.
The Variable view contains properties of the following property scopes.
Axis2-Client Scope Properties
Axis2 Scope Properties
Operation Scope Properties
Synapse Scope Properties
Transport Scope Properties
You can have a list of selected properties out of the above, in the properties table of the Message Envelope tab, and view information on the property keys and values of them as shown below.
Click Add Property, specify the context and name of the property, and then click OK, to add that propert to the properties table in the Message Envelope tab as shown below.
Click Clear Property, to remove a property from the properties table.
Changing the property values
There are three operations that you can perform on message mediation property values as described below.
Injecting new properties
Follow the steps below to inject new properties to the ESB server while debugging.
- Right click on the Variable view, click Inject/Clear Property, and then click Inject Property as shown below.
- Enter the details about the property you prefer to add as shown in the example below.
- Click OK.
Clearing a property
Follow the steps below to clear an existing property from the ESB server.
- Right click on the Variable view, click Inject/Clear Property, and then click Clear Property as shown below.
- Enter the details about the property you want to clear as shown in the example below.
- Click OK.
Modifying a property
Click on the value section of the preferred property and change the value in the Variable view as shown in the example below, to modify it.
Viewing wire logs
While debugging a Synapse flow, you can view the the actual HTTP messages at the entry point of the ESB via wire logs. For example, you can view wire logs of the incoming flow and the final response of a proxy service. Also, you can view wire logs for points, where it goes out from the ESB. For example, you can see the outgoing and incoming wire logs for specific mediators (i.e. Call mediator, Send mediator etc.). Wire logs are useful to troubleshoot unexpected issues, which occurr while integrating miscallaneous systems. You can use wire logs to verify whether the message payload is properly going out from the server, whether the HTTP headers such as the content-type is properly set in the outgoing message etc.
Enabling wire logs
The passthrough HTTP transport is the main transport, which handles HTTP/HTTPS messages in WSO2 ESB. Un-comment the following entry in the
<ESB_HOME/repository/conf/log4j.properties file to enable wire logs for the passthrough HTTP transport:
The above entry is available only in WSO2 ESB 4.7.0 or later versions.
-If you are using WSO2 ESB 4.5.1 or below: Un-comment the following entry in the
Callout mediator uses the Axis2
CommonsHTTPSenderto invoke services. It does not leverage the non-blocking NHTTP/passthrough transports. Therefore, you need to add the following entries to the
<ESB_HOME/repository/conf/log4j.propertiesfile to enable wire logs for the callout mediator.
Following is a sample wirelog.
DEBUG - wire >>- This represents a message, which is coming into WSO2 ESB from the wire
DEBUG - wire <<- This represents a message, which goes to the wire from WSO2 ESB
Viewing wire logs of a specific mediator
You need to put a debug point to the mediator, to view wire logs of it. When debugging is finished (or while debugging), right click on the mediator, and click Show WireLogs, to view wire logs for a specific mediator.
You can only view wire logs for a whole proxy service, call mediator, send mediator, or other API resources. However, you cannot view a wire log of a Synapse config (e.g. sequences), because there would not be anything written to wire, when the flow comes to the sequence etc. Hence, you can only view them in wire entry points.
Viewing wire logs while debugging
If you view wire logs while debugging, you view only the wire logs of mediators, whose execution is already completed as shown in the example below.
Viewing wire logs of a mediator after debugging execution of it
When you view wire logs of a mediator (e.g. send mediator) after debugging, you can view the request and response wire logs as shown in the example below.
Viewing wire logs of a proxy service after debugging
If you view wire logs of a proxy service after debugging finished, you view the request wire log and final response wire log of that proxy as shown in the example below.