jobserv/src/main/java/JobServ/ProcessController.java

/*
 * ProcessController
 *
 * v1.0
 *
 * May 22, 2019
 */

package JobServ;

/*
 * ProcessController
 * This class wraps a java Process object with metadata
 * such as translated PID that exist for this specific API
 * as well as general metadata like IO streams.
 */
class ProcessController {
    // incremented in constructor
    private static int nextPid = 0;
    private int pid;

    // TODO: add an api endpoint for streaming client input into
    // interactive processes (out of scope for initial API)
    private OutputStream output;
    private InputStream input;
    private Scanner outputScanner;

    private Process process;

    /*
     * Constructor
     * Takes a command and spawns it in a new process
     * Redirects IO streams and assigns a fake PID
     */
    public ProcessController(String command) throws IOException {
        this.pid = ProcessController.nextPid;
        ProcessController.nextPid += 1;

        this.process = Runtime.exec(command);
        this.output = this.process.getOutputStream();
        this.input = this.process.getInputStream();
        this.outputScanner = new Scanner(this.input);
        this.outputScanner.useDelimieter("\\A");
    }

    /*
     * getPid()
     * returns translated pid of this process
     */
    public int getPid() {
        return this.pid;
    }

    /*
     * getStatus()
     * returns whether or not the process is running
     * this isnt a very direct way of getting the information
     * The alternative is to use reflection to get into the private UNIXProcess class
     * for the PID and to check that against 'ps' or a similar command
     *
     * TODO: (for future release) return thread state
     */
    public Boolean getStatus() {
        try {
            process.exitValue();
            return true;
        } catch (IllegalThreadStateException e) {
            return false;
        }
    }

    /*
     * getReturn()
     * returns the exit code of the process
     * or 256 if process is still running
     * (unix/posix defines an exit code as a uint8, so 256 is fair game)
     */
    public int getReturn() {
        try {
            return process.exitValue();
        } catch (IllegalThreadStateException e) {
            return 256;
        }
    }

    /*
     * getOutput()
     * gets output from process
     */
    public String getOutput() {
        String out = "";
        while(scanner.hasNext()) {
            out += scanner.next();
        }

        return out;
    }

    /*
     * kill()
     * Cleans up resources and destroys process
     */
    public void kill() {
        this.input.close();
        this.output.close();
        process.destroy();
    }
}