1 files changed, 284 insertions, 0 deletions
diff --git a/api/src/main/java/org/openslx/taskmanager/api/AbstractTask.java b/api/src/main/java/org/openslx/taskmanager/api/AbstractTask.java
new file mode 100644
index 0000000..cc837ba
--- /dev/null
+++ b/api/src/main/java/org/openslx/taskmanager/api/AbstractTask.java
@@ -0,0 +1,284 @@
+package org.openslx.taskmanager.api;
+
+import java.util.UUID;
+
+import org.apache.log4j.Logger;
+import org.openslx.taskmanager.api.TaskStatus.StatusCode;
+
+import com.google.gson.annotations.Expose;
+
+public abstract class AbstractTask implements Runnable
+{
+
+	private static final long RELEASE_DELAY = 5l * 60l * 1000l;
+	private static final Logger LOG = Logger.getLogger( AbstractTask.class );
+
+	/*
+	 * To be set from task invocation (json data)
+	 */
+
+	/**
+	 * The id of the task instance.
+	 */
+	@Expose
+	private String id = null;
+	/**
+	 * Parent task. This task won't be started as long as the parent task currently
+	 * waiting for execution or is being executed. Otherwise this task is available for execution.
+	 * Note that MAX_INSTANCES is still being taken into account. Set to null to ignore.
+	 */
+	@Expose
+	private String parentTask = null;
+	/**
+	 * If the parent task failed to execute, don't run this task and fail immediately.
+	 */
+	@Expose
+	private boolean failOnParentFail = true;
+
+	/*
+	 * Variables we're working with - these should never be set from incoming (json) data
+	 */
+
+	/**
+	 * Maximum age of a task, if it's not freed explicitly.
+	 */
+	private static final long MAX_TASK_AGE = 24l * 3600l * 1000l;
+	/**
+	 * timeMillis when this task will be removed. This will be set automatically to something
+	 * reasonable like 24 hours, once the job has finished. This is to prevent clogging the task
+	 * manager with finished jobs over time. Note that you can explicitly remove a job using the
+	 * "release" command.
+	 */
+	private volatile long removalDeadline = System.currentTimeMillis() + MAX_TASK_AGE;
+	/**
+	 * True if init() has been called. Task will not start if this is false.
+	 */
+	private volatile boolean initDone = false;
+	/**
+	 * Status of Task
+	 */
+	private TaskStatus status = TaskStatus.ts_waiting;
+	/**
+	 * Reference to parent task
+	 */
+	private AbstractTask parent = null;
+
+	/**
+	 * Default constructor which should not be overridden
+	 */
+	public AbstractTask()
+	{
+		this.id = UUID.randomUUID().toString();
+	}
+
+	/*
+	 * Overridable methods
+	 */
+
+	/**
+	 * Initialize the task; method used by the {@link Taskmanager}.
+	 * Put your own initialization code in initTask()
+	 */
+	public final boolean init( AbstractTask parent )
+	{
+		if ( this.initDone ) {
+			LOG.fatal( "init() called twice on " + this.getClass().getSimpleName() );
+			System.exit( 1 );
+		}
+		this.parent = parent;
+		this.status = new TaskStatus( StatusCode.TASK_WAITING, this.id );
+		this.initDone = true;
+		boolean ret;
+		try {
+			ret = this.initTask();
+		} catch ( Throwable t ) {
+			ret = false;
+		}
+		if ( !ret ) {
+			this.status.statusCode = StatusCode.TASK_ERROR;
+		}
+		return ret;
+	}
+
+	/**
+	 * Your own initialization code. This is run synchronously within the network
+	 * handling thread, so do NOT put anything here that might take longer than a few milliseconds!
+	 * You should usually only validate the input to the task here, and return false if it is
+	 * invalid.
+	 * 
+	 * @return - true if the task should be executed by the scheduler (ie init was successful)
+	 *         - false if init was not successful, or you don't need to do any more processing
+	 */
+	protected abstract boolean initTask();
+
+	/**
+	 * This is where you put your huge work stuff that takes ages.
+	 */
+	protected abstract boolean execute();
+
+	/*
+	 * Final methods
+	 */
+
+	/**
+	 * Get id of parent task.
+	 * 
+	 * @return id of parent task, null if no parent set
+	 * 
+	 */
+	public String getParentTaskId()
+	{
+		return this.parentTask;
+	}
+
+	/**
+	 * Set the custom status data object to be returned on status requests.
+	 * For simple tasks it should be sufficient to set this once before executing
+	 * the task starts, and then just update fields in that class while the
+	 * task is running. For cases where you have complicated data structures or
+	 * multiple values that need to stay in sync you could create a new instance
+	 * every time, fill it with values, and then call this method.
+	 * 
+	 * @param obj the object containing you specific task data
+	 */
+	protected final void setStatusObject( Object obj )
+	{
+		status.setStatusObject( obj );
+	}
+
+	/**
+	 * Get current status of task.
+	 */
+	public final TaskStatus getStatus()
+	{
+		if ( this.initDone && this.parentTask != null ) {
+			final StatusCode parentStatus = parent.getStatusCode();
+			switch ( parentStatus ) {
+			case DUPLICATE_ID:
+			case NO_SUCH_INSTANCE:
+			case NO_SUCH_TASK:
+			case NO_SUCH_CONSTRUCTOR:
+			case PARENT_FAILED:
+			case TASK_ERROR:
+				if ( this.failOnParentFail )
+					this.status.statusCode = StatusCode.PARENT_FAILED;
+				this.parentTask = null;
+				break;
+			default:
+				break;
+			}
+		}
+		return this.status;
+	}
+
+	/**
+	 * Get status code if task.
+	 * 
+	 * @return
+	 */
+	public final StatusCode getStatusCode()
+	{
+		return getStatus().getStatusCode();
+	}
+
+	/**
+	 * Get id of task
+	 */
+	public final String getId()
+	{
+		return this.id;
+	}
+
+	/**
+	 * Getter for failOnParentTask
+	 */
+	public final boolean getFailOnParentFail()
+	{
+		return this.failOnParentFail;
+	}
+
+	/**
+	 * Release the task: If the task is still pending/running, it will be removed from the task
+	 * manager as soon as it finishes. So you can't query for its result later. If the task has
+	 * already finished (either successful or failed), it will be removed (almost) immediately.
+	 */
+	public final void release()
+	{
+		this.removalDeadline = Math.min( this.removalDeadline, System.currentTimeMillis() + RELEASE_DELAY );
+	}
+
+	/**
+	 * Can this task be started? This checks all the conditions:
+	 * - Has this task been initialized yet?
+	 * - Is it actually waiting for execution?
+	 * - Does it depend on a parent task?
+	 * -- If so, did the parent finish?
+	 * -- Or did it fail?
+	 * --- If so, should this task only run if it didn't fail?
+	 * 
+	 * @return true iff this task can be started
+	 */
+	public final boolean canStart()
+	{
+		if ( !this.initDone || this.id == null || this.getStatus().getStatusCode() != StatusCode.TASK_WAITING ) {
+			return false;
+		}
+		if ( this.parent == null )
+			return true;
+		return parent.getStatusCode() != StatusCode.TASK_WAITING && parent.getStatusCode() != StatusCode.TASK_PROCESSING;
+	}
+
+	/**
+	 * Checks whether this task can be removed from the task manager.
+	 * A task can be removed if it is not executing or waiting for execution, and
+	 * its removal deadline has been reached.
+	 * 
+	 * @return true if it can be released
+	 */
+	public final boolean canBeReleased()
+	{
+		if ( this.status.statusCode == StatusCode.TASK_WAITING || this.status.statusCode == StatusCode.TASK_PROCESSING )
+			return false;
+		return this.removalDeadline != 0 && System.currentTimeMillis() > this.removalDeadline;
+	}
+
+	/**
+	 * Execute the task, wrapped in some sanity checks.
+	 */
+	@Override
+	public final void run()
+	{
+		synchronized ( this ) {
+			if ( this.status.statusCode != StatusCode.TASK_WAITING )
+				throw new RuntimeException( "Tried to launch task " + this.getClass().getSimpleName() + " twice!" );
+			if ( !this.initDone )
+				throw new RuntimeException( "Tried to launch " + this.getClass().getSimpleName() + " without initializing it!" );
+			this.status.statusCode = StatusCode.TASK_PROCESSING;
+		}
+		boolean ret;
+		try {
+			ret = execute();
+		} catch ( Throwable t ) {
+			LOG.warn( "Task " + this.getClass().getSimpleName() + " failed with uncaught exception: " + t.toString() );
+			ret = false;
+		}
+		if ( ret ) {
+			this.status.statusCode = StatusCode.TASK_FINISHED;
+		} else {
+			this.status.statusCode = StatusCode.TASK_ERROR;
+		}
+	}
+
+	/**
+	 * This is called when a client requests the status of this task. In case you
+	 * want to return complex structures like Lists, which are not thread safe, you
+	 * might want to keep that list outside the status class you return, and only
+	 * create a copy of it for the status class in this function.
+	 * If you only return more or less atomic data, you don't need to override
+	 * this function
+	 */
+	protected void updateStatus()
+	{
+
+	}
+}