JVM 9+ No Way to Enable Remote Debugging

[edeesis]

Expected Behavior

In JDK 9, the agentlib options for address changed from requiring simply a port number to allowing a full address (host and port) to be specified.

This change caused the following debug string:

-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005

to only bind to 127.0.0.1 in JDK 9, compared to JDK 8 which would bind to 0.0.0.0.

The correct format to keep this behavior is

-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005

Sources (couldn't find an official source):

https://www.baeldung.com/java-application-remote-debugging#from-java9
https://www.jetbrains.com/help/idea/debug-a-java-application-using-a-dockerfile.html#create-remote-debug-config

While most people are debugging locally, this becomes a problem especially when using Docker - which needs 0.0.0.0 to be bound to allow the host to communicate over the internal docker network.

Current Behavior

Using the --jvm-debug parameter sets

-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005

and only the server, suspend, and port can be overriden, instead of the whole address. In addition, port is an Integer, so you can't specify *:5005

Context

Workaround:

tasks {
    run {
        jvmArgs = ["-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005"]
    }
}

Suggested solution:

Add a new property to https://docs.gradle.org/current/javadoc/org/gradle/process/JavaDebugOptions.html to specify the address.

gradle/subprojects/core/src/main/java/org/gradle/process/internal/JvmOptions.java

Line 153 in 5ec3f67

args.add("-agentlib:jdwp=transport=dt_socket,server=" + (server ? 'y' : 'n') + ",suspend=" + (suspend ? 'y' : 'n') + ",address=" + port);

        if (debugOptions.getEnabled().get()) {
            boolean server = debugOptions.getServer().get();
            boolean suspend = debugOptions.getSuspend().get();
            int port = debugOptions.getPort().get();
            String address = debugOptions.getAddress().get()
            args.add("-agentlib:jdwp=transport=dt_socket,server=" + (server ? 'y' : 'n') + ",suspend=" + (suspend ? 'y' : 'n') + ",address=" + (address != null ? address + ":" : "") + port);
        }

Alternatively, the address could take priority over the port.

        if (debugOptions.getEnabled().get()) {
            boolean server = debugOptions.getServer().get();
            boolean suspend = debugOptions.getSuspend().get();
            int port = debugOptions.getPort().get();
            String address = debugOptions.getAddress().get()
            args.add("-agentlib:jdwp=transport=dt_socket,server=" + (server ? 'y' : 'n') + ",suspend=" + (suspend ? 'y' : 'n') + ",address=" + (address != null ? address : port));
        }

[h0tk3y]

The suggested fix is:

• Add a property to JavaDebugOptions:

  /**
   * The address of the debugger server.
   * If the value is not set, then only the port will be passed in the debugger options.
   *
   * @since 7.6
   */
  @Incubating
  @Optional
  @Input Property<String> getHost();

  It won't have any value by default, and the absence of the value will lead to the current behavior – no host name passed to JDWP → loopback only on Java 9+, and all interfaces on older versions.

  If present, the string will be passed in the JDWP arguments address= part, always followed by :$port (so the host name should not include the port). It will be possible to use the value "*" for host, meaning that the server should bind on all interfaces.

• Similarly, support debugging the Gradle build remotely by introducing the property org.gradle.debug.host with the same semantics as the one described above.