Master Shell Scheduling with DolphinScheduler and ProcessBuilder | HackerNoon

Learn how to execute and monitor Shell scripts efficiently with sudo support, working directories, and full logging control.

In this article, we’ll dive deep into how DolphinScheduler uses ProcessBuilder to execute shell commands. By default, DolphinScheduler wraps shell scripts using BashShellInterceptorBuilder, generating execution commands that support both standard and sudo modes.

We’ll also walk through a Spring Boot example showing how to configure working directories, merge output streams, monitor process execution, and output logs — helping you achieve efficient Shell task management and scheduling.

1. How DolphinScheduler Uses ProcessBuilder

1.1. Wrapping Shell Commands

In DolphinScheduler, the command wrapping happens inside:

org.apache.dolphinscheduler.plugin.task.api.shell.ShellInterceptorBuilderFactory

public class ShellInterceptorBuilderFactory {

    private final static String INTERCEPTOR_TYPE = PropertyUtils.getString("shell.interceptor.type", "bash");

    @SuppressWarnings("unchecked")
    public static IShellInterceptorBuilder newBuilder() {
        // Default logic
        if (INTERCEPTOR_TYPE.equalsIgnoreCase("bash")) {
            return new BashShellInterceptorBuilder();
        }
        if (INTERCEPTOR_TYPE.equalsIgnoreCase("sh")) {
            return new ShShellInterceptorBuilder();
        }
        if (INTERCEPTOR_TYPE.equalsIgnoreCase("cmd")) {
            return new CmdShellInterceptorBuilder();
        }
        throw new IllegalArgumentException("Unsupported shell type: " + INTERCEPTOR_TYPE);
    }
}

✅ By default, BashShellInterceptorBuilder is used.

Here’s the relevant part:

org.apache.dolphinscheduler.plugin.task.api.shell.bash.BashShellInterceptorBuilder

public class BashShellInterceptorBuilder
        extends BaseLinuxShellInterceptorBuilder<BashShellInterceptorBuilder, BashShellInterceptor> {

    @Override
    public BashShellInterceptorBuilder newBuilder() {
        return new BashShellInterceptorBuilder();
    }

    @Override
    public BashShellInterceptor build() throws FileOperateException, IOException {
        // Core part: Generate shell script
        generateShellScript();
        List<String> bootstrapCommand = generateBootstrapCommand();
        // Instantiate BashShellInterceptor
        return new BashShellInterceptor(bootstrapCommand, shellDirectory);
    }

    @Override
    protected String shellInterpreter() {
        return "bash";
    }

    @Override
    protected String shellExtension() {
        return ".sh";
    }

    @Override
    protected String shellHeader() {
        return "#!/bin/bash";
    }
}

Command generation happens here:

org.apache.dolphinscheduler.plugin.task.api.shell.BaseLinuxShellInterceptorBuilder#generateBootstrapCommand

protected List<String> generateBootstrapCommand() {
    if (sudoEnable) {
        // sudo -u tenant -i /opt/xx.sh
        return bootstrapCommandInSudoMode();
    }
    // bash /opt/xx.sh
    return bootstrapCommandInNormalMode();
}

Two paths:

• Normal Mode (bash /path/to/script.sh)
• Sudo Mode (sudo -u tenant -i /path/to/script.sh)

Example of sudo mode:

private List<String> bootstrapCommandInSudoMode() {
    List<String> bootstrapCommand = new ArrayList<>();
    bootstrapCommand.add("sudo");
    if (StringUtils.isNotBlank(runUser)) {
        bootstrapCommand.add("-u");
        bootstrapCommand.add(runUser);
    }
    bootstrapCommand.add("-i");
    bootstrapCommand.add(shellAbsolutePath().toString());
    return bootstrapCommand;
}

1.2. Executing the Shell Command

The real execution is handled here:

org.apache.dolphinscheduler.plugin.task.api.shell.BaseShellInterceptor

public abstract class BaseShellInterceptor implements IShellInterceptor {

    protected final String workingDirectory;
    protected final List<String> executeCommands;

    protected BaseShellInterceptor(List<String> executeCommands, String workingDirectory) {
        this.executeCommands = executeCommands;
        this.workingDirectory = workingDirectory;
    }

    @Override
    public Process execute() throws IOException {
        ProcessBuilder processBuilder = new ProcessBuilder();
        processBuilder.directory(new File(workingDirectory));  // Set working directory (important for loading JARs etc.)
        processBuilder.redirectErrorStream(true);              // Merge error stream into output stream
        processBuilder.command(executeCommands);
        log.info("Executing shell command: {}", String.join(" ", executeCommands));
        return processBuilder.start();
    }
}

2. Practical Example: Shell Scheduling Made Easy

Let’s build a simple Spring Boot application that launches a Shell script!

2.1. pom.xml Dependency

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter</artifactId>
  <version>2.6.1</version>
</dependency>

2.2. Spring Boot Application Code

@SpringBootApplication
public class Application {

    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class, args);

        List<String> executeCommands = new ArrayList<>();
        executeCommands.add("sudo");
        executeCommands.add("-u");
        executeCommands.add("qiaozhanwei");
        executeCommands.add("-i");
        executeCommands.add("/opt/test/my.sh");

        ProcessBuilder processBuilder = new ProcessBuilder();
        processBuilder.directory(new File("/opt/test"));  // Set working directory
        processBuilder.redirectErrorStream(true);         // Merge error output into standard output
        processBuilder.command(executeCommands);

        Process process = processBuilder.start();

        try (BufferedReader inReader = new BufferedReader(new InputStreamReader(process.getInputStream()))) {
            String line;
            while ((line = inReader.readLine()) != null) {
                // Print each line of output
                System.out.println(line);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        // Wait for 10 minutes maximum
        boolean status = process.waitFor(10, TimeUnit.MINUTES);
        System.out.println("Execution status -> " + status);
    }
}

2.3. Example Log Output

The logs show:

• The Shell script was executed successfully
• Standard and error outputs were captured
• The process finished within 10 minutes

Snippet:

Executing shell command : sudo -u qiaozhanwei -i /opt/test/my.sh
...
Job job_1694766249884_0931 completed successfully
status ->true

Process finished with exit code 0

Final Thoughts

Using DolphinScheduler + ProcessBuilder, you can flexibly handle Shell task execution with full control over:

• Working directories
• Error/standard output streams
• Sudo permissions
• Timeout monitoring

This approach is simple, robust, and easy to extend — a must-have skill if you’re managing Shell-based workflows in big data or DevOps scenarios!