Chapter 4. Debugging Eclipse Vert.x based application

Procedure

1. In a console, navigate to the directory with your application.

2. Launch your application and specify the debug port using the -Ddebug.port argument:

   $ mvn vertx:debug -Ddebug.port=$PORT_NUMBER

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   Here, $PORT_NUMBER is an unused port number of your choice. Remember this number for the remote debugger configuration.

   Use the -Ddebug.suspend=true argument to make the application wait until a debugger is attached to start.

Procedure

1. Using the oc command, list the available deployment configurations:

   $ oc get dc

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2. Set the JAVA_DEBUG environment variable in the deployment configuration of your application to true, which configures the JVM to open the port number 5005 for debugging. For example:

   $ oc set env dc/MY_APP_NAME JAVA_DEBUG=true

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3. Redeploy the application if it is not set to redeploy automatically on configuration change. For example:

   $ oc rollout latest dc/MY_APP_NAME

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4. Configure port forwarding from your local machine to the application pod:

   1. List the currently running pods and find one containing your application:

      $ oc get pod
      NAME                            READY     STATUS      RESTARTS   AGE
      MY_APP_NAME-3-1xrsp          0/1       Running     0          6s
      ...

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   2. Configure port forwarding:

      $ oc port-forward MY_APP_NAME-3-1xrsp $LOCAL_PORT_NUMBER:5005

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      Here, $LOCAL_PORT_NUMBER is an unused port number of your choice on your local machine. Remember this number for the remote debugger configuration.

5. When you are done debugging, unset the JAVA_DEBUG environment variable in your application pod. For example:

   $ oc set env dc/MY_APP_NAME JAVA_DEBUG-

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Procedure

1. Start Red Hat CodeReady Studio.

2. Create a new debug configuration for your application:

   1. Click Run→Debug Configurations.
   2. In the list of configurations, double-click Remote Java application. This creates a new remote debugging configuration.
   3. Enter a suitable name for the configuration in the Name field.
   4. Enter the path to the directory with your application into the Project field. You can use the Browse…​ button for convenience.
   5. Set the Connection Type field to Standard (Socket Attach) if it is not already.
   6. Set the Port field to the port number that your application is listening on for debugging.
   7. Click Apply.

3. Start debugging by clicking the Debug button in the Debug Configurations window.

   To quickly launch your debug configuration after the first time, click Run→Debug History and select the configuration from the list.

1. To add logging to your application, create a io.vertx.core.logging.Logger:

   Logger logger = LoggerFactory.getLogger(className);
   
   logger.info("something happened");
   logger.error("oops!", exception);
   logger.debug("debug message");
   logger.warn("warning");

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   Important

   Logging backends use different formats to represent replaceable tokens in parameterized messages. If you rely on parameterized logging methods, you will not be able to switch logging backends without changing your code.

1. Set the value of the vertx.logger-delegate-factory-class-name system property to the name of the class that implements the LogDelegateFactory interface. Eclipse Vert.x provides the pre-built implementations for the following libraries with their corresponding pre-defined classnames listed below:

   Expand

   Library	Class name
   Log4J v1	io.vertx.core.logging.Log4jLogDelegateFactory
   Log4J v2	io.vertx.core.logging.Log4j2LogDelegateFactory
   SLF4J	io.vertx.core.logging.SLF4JLogDelegateFactory

   Show more

   When implementing logging using a custom library, ensure that the relevant Log4J or SLF4J jars are included among the dependencies for your application.

   Important

   The Log4J v1 delegate provided with Eclipse Vert.x does not support parameterized messages. The delegates for Log4J v2 and SLF4J both use the {} syntax. The java.util.logging delegate relies on java.text.MessageFormat that uses the {n} syntax.

1. SLF4J
2. Log4J
3. java.util.logging as a fallback option

Procedure

1. Deploy your application to OpenShift:

   $ mvn clean oc:deploy -Popenshift

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2. View the logs:

   1. Get the name of the pod with your application:

      $ oc get pods

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   2. Start watching the log output:

      $ oc logs -f pod/MY_APP_NAME-2-aaaaa

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      Keep the terminal window displaying the log output open so that you can watch the log output.

3. Interact with your application:

   For example, the following command is based on an example REST API level 0 application where debug logging is set to log the message variable in the /api/greeting method:

   1. Get the route of your application:

      $ oc get routes

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   2. Make an HTTP request on the /api/greeting endpoint of your application:

      $ curl $APPLICATION_ROUTE/api/greeting?name=Sarah

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4. Return to the window with your pod logs and inspect debug logging messages in the logs.

   ...
   Feb 11, 2017 10:23:42 AM io.openshift.MY_APP_NAME
   INFO: Greeting: Hello, Sarah
   ...

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5. To disable debug logging, update your logging configuration file, for example src/main/resources/vertx-default-jul-logging.properties, remove the logging configuration for your class and redeploy your application.