Extra whitespaces in debug opts in alluxio-env.sh causes processes to fail to start

[dbw9580]

Alluxio Version:
Current main

Describe the bug

Alluxio processes fail to start if ALLUXIO_*_ATTACH_OPTS is set and contains a leading or trailing whitespace.

logs/worker.out says Error: Could not find or load main class. No class name is included in this error message.

To Reproduce

1. Enable the Java debugger to attach to Alluxio processes e.g. the worker, by setting ALLUXIO_WORKER_ATTACH_OPTS to -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=60003, with a leading whitespace, in conf/alluxio-env.sh.
2. Start the worker process by running bin/alluxio process start worker
3. Wait for the worker to start.

Expected behavior

The worker process should start normally, with the debugging port open.

Urgency
Normal

Are you planning to fix it
No

Additional context

alluxio/cli/src/alluxio.org/cli/processes/worker.go

Lines 73 to 77 in 8329244

	func (p *WorkerProcess) Start(cmd *env.StartProcessCommand) error {
	cmdArgs := []string{env.Env.EnvVar.GetString(env.ConfJava.EnvVar)}
	if attachOpts := env.Env.EnvVar.GetString(confAlluxioWorkerAttachOpts.EnvVar); attachOpts != "" {
	cmdArgs = append(cmdArgs, strings.Split(attachOpts, " ")...)
	}

The launcher prepends the attach opts to the command, by first splitting the opts with a whitespace as the delimiter. In the case where the opts string contains a leading whitespace, there is a empty string after the split. This empty string is then passed to the java command as a positional argument, which interprets it as the name of a main class.

Since alluxio-env.sh is a shell script, a user can reasonably expect to set the options with a leading whitespace as they are usually concatenated to form a longer command line. Not respecting this convention may be surprising.

[dbw9580]

@Xenorith FYI.

[Xenorith]

fixed by #18252