How to get GC logs? - Tencent Cloud

To obtain GC (Garbage Collection) logs, you typically need to configure the Java Virtual Machine (JVM) to generate these logs when running your Java application. Here’s how you can do it:

Command Line Arguments: You can enable GC logging by adding specific JVM arguments when starting your Java application. The most commonly used arguments are:
- -Xloggc:<path-to-gc-log-file>: Specifies the file where GC logs will be written.
- -XX:+PrintGCDetails: Provides detailed information about each garbage collection event.
- -XX:+PrintGCDateStamps: Adds a timestamp to each GC event in the log.
- -XX:+UseGCLogFileRotation: Enables rotation of GC log files.
- -XX:NumberOfGCLogFiles=<number>: Sets the number of GC log files to keep.
- -XX:GCLogFileSize=<size>: Sets the maximum size of each GC log file.
Example:
```
java -Xloggc:/path/to/gc.log -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M -jar myapp.jar
```
Environment Variables: Some environments allow you to set these options through environment variables or configuration files.
Application Servers: If you are running your Java application on an application server like Apache Tomcat, you can configure these settings in the server’s startup script or configuration file.

For cloud-based deployments, if you are using a managed service, the process might be slightly different. For example, if you are deploying a Java application on Tencent Cloud’s Cloud Container Service (TKE), you can configure these JVM arguments in the container’s startup command or environment variables.

Example with Tencent Cloud:

In TKE, you can specify the JVM arguments in the command or args section of your container configuration in the Kubernetes deployment YAML file.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-java-app
spec:
  replicas: 1
  selector:
    matchLabels:
      app: my-java-app
  template:
    metadata:
      labels:
        app: my-java-app
    spec:
      containers:
      - name: my-java-app
        image: my-java-app-image
        command: ["java"]
        args: [
          "-Xloggc:/path/to/gc.log",
          "-XX:+PrintGCDetails",
          "-XX:+PrintGCDateStamps",
          "-XX:+UseGCLogFileRotation",
          "-XX:NumberOfGCLogFiles=5",
          "-XX:GCLogFileSize=2M",
          "-jar", "myapp.jar"
        ]

This configuration ensures that GC logs are generated and stored in the specified file, providing valuable insights into the garbage collection behavior of your Java application.