Document Details

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# [Windows](#tab/windows)

To show the current Java version, run the following command in [Azure Cloud Shell](https://shell.azure.com):

Execute the following command to start a 30-second recording of the JVM. It profiles the JVM and creates a Java Flight Recorder (JFR) file named `jfr_example.jfr` in the home directory. Replace `116` with the PID of your Java app.

# [Windows](#tab/windows)

#### Timed recording

To take a timed recording, you need the process ID (PID) of the Java application. To find the PID, open your service in the Azure portal. Select **Development Tools** > **Advanced Tools**, then select **Go**. In Kudu, select **Process explorer**. This page shows the running processes in your web app. Find the process named "java" in the table and copy the corresponding PID.

Next, open the **Debug Console** in the top toolbar of the SCM site and run the following command. Replace `<pid>` with the PID you copied earlier. This command starts a 30-second profiler recording of your Java application and generates a file named `timed_recording_example.jfr` in the `C:\home` directory.

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### Precompile JSP files

To improve performance of Tomcat applications, you can compile your JSP files before deploying to App Service. You can use the [Maven plugin](https://sling.apache.org/components/jspc-maven-plugin/plugin-info.html) provided by Apache Sling, or use [this Ant build file](https://tomcat.apache.org/tomcat-9.0-doc/jasper-howto.html#Web_Application_Compilation).

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[!INCLUDE [robots933456](../../includes/app-service-web-configure-robots933456.md)]

## <a name = "choosing-a-java-runtime-version"></a> Choose a Java runtime version

App Service allows users to choose the major version of the JVM, such as Java 8 or Java 11, and the patch version, like 1.8.0_232 or 11.0.5. You can also choose to have the patch version update automatically as new minor versions become available. In most cases, production apps should use pinned patch JVM versions, which prevent unanticipated outages during a patch version autoupdate. All Java web apps use 64-bit JVMs, and it's not configurable.

::: zone pivot="java-tomcat"

If you're using Tomcat, you can choose to pin the patch version of Tomcat. On Windows, you can pin the patch versions of the JVM and Tomcat independently. On Linux, you can pin the patch version of Tomcat. The patch version of the JVM is also pinned but isn't separately configurable.

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If you choose to pin the minor version, you need to periodically update the JVM minor version on the app. To ensure that your application runs on the newer minor version, create a staging slot and increment the minor version on the staging slot. After you confirm that the application runs correctly on the new minor version, you can swap the staging and production slots.

::: zone pivot="java-jboss"

## Run the JBoss CLI

In your JBoss EAP app's SSH session, you can run the JBoss CLI with the following command:

* `directory` is set to `AZURE_LOGGING_DIR`, which defaults to `home\logFiles`.
* `maxDays` is set to `WEBSITE_HTTPLOGGING_RETENTION_DAYS`, which defaults to `7`. This value aligns with the application-logging platform default.
 
On Linux, it has all of the same customization, and it adds some error and reporting pages to the valve: