Tutorial: Debug a Java application deployed on a local Service Fabric cluster

Article
08/22/2024

This tutorial is part two of a series. You learn how to attach a remote debugger using Eclipse for the Service Fabric application. Additionally, you learn how to redirect logs from the running applications to a location convenient for the developer.

In this tutorial series you learn how to:

Build a Java Service Fabric Reliable Services application
Deploy and debug the application on a local cluster
Deploy application to an Azure cluster
Set up monitoring and diagnostics for the application
Set up CI/CD

In part two of the series, you learn how to:

Debug Java application using Eclipse
Redirect logs to a configurable location

Prerequisites

Before you begin this tutorial:

Set up your development environment for Mac or Linux. Follow the instructions to install the Eclipse plug-in, Gradle, the Service Fabric SDK, and the Service Fabric CLI (sfctl).

Download the Voting sample application

If you did not build the Voting sample application in part one of this tutorial series, you can download it. In a command window, run the following command to clone the sample app repository to your local machine.

git clone https://github.com/Azure-Samples/service-fabric-java-quickstart

Build and deploy the application to the local development cluster.

Debug Java application using Eclipse

Open the Eclipse IDE on your machine and click on File -> Import....
In the popup window, select the General -> Existing Projects into Workspace option and press Next.
In the Import Projects window, choose the Select root directory option and pick the Voting directory. If you followed tutorial series one, the Voting directory is in the Eclipse-workspace directory.
Update entryPoint.sh of the service you wish to debug, so that it starts the Java process with remote debug parameters. For this tutorial the stateless front end is used: Voting/VotingApplication/VotingWebPkg/Code/entryPoint.sh. Port 8001 is set for debugging in this example.
```
java -Xdebug -Xrunjdwp:transport=dt_socket,address=8001,server=y,suspend=n -Djava.library.path=$LD_LIBRARY_PATH -jar VotingWeb.jar
```
Update the Application Manifest by setting the instance count or the replica count for the service that is being debugged to one. This setting avoids conflicts for the port that is used for debugging. For example, for stateless services, set InstanceCount="1" and for stateful services set the target and min replica set sizes to 1 as follows: TargetReplicaSetSize="1" MinReplicaSetSize="1".
In the Eclipse IDE, select Run -> Debug Configurations -> Remote Java Application, press the New button, set the properties as follows and click Apply.
```
Name: Voting
Project: Voting
Connection Type: Standard
Host: localhost
Port: 8001
```
Put a breakpoint on line 109 of the Voting/VotingWeb/src/statelessservice/HttpCommunicationListener.java file.
In the Package Explorer, right click on the Voting project and click Service Fabric -> Publish Application ...
In the Publish Application window, select Local.json from the dropdown, and click Publish.
In the Eclipse IDE, select Run -> Debug Configurations -> Remote Java Application, click on the Voting configuration you created and click Debug.
Go to your web browser and access localhost:8080. This will automatically hit the breakpoint and Eclipse will enter the Debug perspective.

Now you can apply these same steps to debug any Service Fabric application in Eclipse.

Redirect application logs to custom location

The following steps walk through how to redirect the application logs from the default /var/log/syslog location to a custom location.

Currently, applications running in Service Fabric Linux clusters only support picking up a single log file. To set up an application so that the logs always go to /tmp/mysfapp0.0.log, create a file named logging.properties in the following location Voting/VotingApplication/VotingWebPkg/Code/logging.properties and add the following content.

handlers = java.util.logging.FileHandler

java.util.logging.FileHandler.level = ALL
java.util.logging.FileHandler.formatter = java.util.logging.SimpleFormatter

# This value specifies your custom location.
# You will have to ensure this path has read and write access by the process running the SF Application
java.util.logging.FileHandler.pattern = /tmp/mysfapp0.0.log

Add the following parameter in the Voting/VotingApplication/VotingWebPkg/Code/entryPoint.sh for the Java execution command:
```
-Djava.util.logging.config.file=logging.properties
```
The following example shows a sample execution with the debugger attached, similar to the execution in the previous section.
```
java -Xdebug -Xrunjdwp:transport=dt_socket,address=8001,server=y,suspend=n -Djava.library.path=$LD_LIBRARY_PATH -Djava.util.logging.config.file=logging.properties -jar VotingWeb.jar
```

At this stage, you have learned how to debug and access your application logs while developing your Service Fabric Java applications.

Next steps

In this part of the tutorial, you learned how to:

Debug Java application using Eclipse
Redirect logs to a configurable location

Advance to the next tutorial:

Deploy application to Azure

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