Bug 42042: Copy org.apache.log4j.scheduler to component project
git-svn-id: https://svn.apache.org/repos/asf/logging/sandbox/log4j/component@527664 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/main/java/org/apache/log4j/scheduler/Job.java b/src/main/java/org/apache/log4j/scheduler/Job.java
new file mode 100644
index 0000000..a0e9be4
--- /dev/null
+++ b/src/main/java/org/apache/log4j/scheduler/Job.java
@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.log4j.scheduler;
+
+
+/**
+ * Job is a very simple interface. It only has a single method {@link #execute}
+ * which is called by the {@link Scheduler} when a task is ready for execution.
+ * <p/>
+ * It is assumed that the execution context
+ * are contained within the implementing
+ * {@link Job} itself.
+ *
+ * @author Ceki Gülcü
+ */
+public interface Job {
+ /**
+ * Execute job.
+ */
+ void execute();
+}
diff --git a/src/main/java/org/apache/log4j/scheduler/Scheduler.java b/src/main/java/org/apache/log4j/scheduler/Scheduler.java
new file mode 100644
index 0000000..72809f7
--- /dev/null
+++ b/src/main/java/org/apache/log4j/scheduler/Scheduler.java
@@ -0,0 +1,307 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.log4j.scheduler;
+
+import java.util.List;
+import java.util.Vector;
+
+/**
+ * A simple but still useful implementation of a Scheduler (in memory only).
+ * <p/>
+ * This implementation will work very well when the number of scheduled job is
+ * small, say less than 100 jobs. If a larger number of events need to be
+ * scheduled, than a better adapted data structure for the jobList can give
+ * improved performance.
+ *
+ * @author Ceki
+ */
+public class Scheduler extends Thread {
+
+ /**
+ * Job list.
+ */
+ List jobList;
+ /**
+ * If set true, scheduler has or should shut down.
+ */
+ boolean shutdown = false;
+
+ /**
+ * Create new instance.
+ */
+ public Scheduler() {
+ super();
+ jobList = new Vector();
+ }
+
+ /**
+ * Find the index of a given job.
+ * @param job job
+ * @return -1 if the job could not be found.
+ */
+ int findIndex(final Job job) {
+ int size = jobList.size();
+ boolean found = false;
+
+ int i = 0;
+ for (; i < size; i++) {
+ ScheduledJobEntry se = (ScheduledJobEntry) jobList.get(i);
+ if (se.job == job) {
+ found = true;
+ break;
+ }
+ }
+ if (found) {
+ return i;
+ } else {
+ return -1;
+ }
+ }
+
+ /**
+ * Delete the given job.
+ * @param job job.
+ * @return true if the job could be deleted, and
+ * false if the job could not be found or if the Scheduler is about to
+ * shutdown in which case deletions are not permitted.
+ */
+ public synchronized boolean delete(final Job job) {
+ // if already shutdown in the process of shutdown, there is no
+ // need to remove Jobs as they will never be executed.
+ if (shutdown) {
+ return false;
+ }
+ int i = findIndex(job);
+ if (i != -1) {
+ ScheduledJobEntry se = (ScheduledJobEntry) jobList.remove(i);
+ if (se.job != job) { // this should never happen
+ new IllegalStateException("Internal programming error");
+ }
+ // if the job is the first on the list,
+ // then notify the scheduler thread to schedule a new job
+ if (i == 0) {
+ this.notifyAll();
+ }
+ return true;
+ } else {
+ return false;
+ }
+ }
+
+
+ /**
+ * Schedule a {@link Job} for execution at system time given by
+ * the <code>desiredTime</code> parameter.
+ * @param job job to schedule.
+ * @param desiredTime desired time of execution.
+ */
+ public synchronized void schedule(final Job job,
+ final long desiredTime) {
+ schedule(new ScheduledJobEntry(job, desiredTime));
+ }
+
+ /**
+ * Schedule a {@link Job} for execution at system time given by
+ * the <code>desiredTime</code> parameter.
+ * <p/>
+ * The job will be rescheduled. It will execute with a frequency determined
+ * by the period parameter.
+ * @param job job to schedule.
+ * @param desiredTime desired time of execution.
+ * @param period repeat period.
+ */
+ public synchronized void schedule(final Job job,
+ final long desiredTime,
+ final long period) {
+ schedule(new ScheduledJobEntry(job, desiredTime, period));
+ }
+
+ /**
+ * Change the period of a job. The original job must exist for its period
+ * to be changed.
+ * <p/>
+ * The method returns true if the period could be changed, and false
+ * otherwise.
+ * @param job job.
+ * @param newPeriod new repeat period.
+ * @return true if period could be changed.
+ */
+ public synchronized boolean changePeriod(final Job job,
+ final long newPeriod) {
+ if (newPeriod <= 0) {
+ throw new IllegalArgumentException(
+ "Period must be an integer langer than zero");
+ }
+
+ int i = findIndex(job);
+ if (i == -1) {
+ return false;
+ } else {
+ ScheduledJobEntry se = (ScheduledJobEntry) jobList.get(i);
+ se.period = newPeriod;
+ return true;
+ }
+ }
+
+ /**
+ * Schedule a job.
+ * @param newSJE new job entry.
+ */
+ private synchronized void schedule(final ScheduledJobEntry newSJE) {
+ // disallow new jobs after shutdown
+ if (shutdown) {
+ return;
+ }
+ int max = jobList.size();
+ long desiredExecutionTime = newSJE.desiredExecutionTime;
+
+ // find the index i such that timeInMillis < jobList[i]
+ int i = 0;
+ for (; i < max; i++) {
+
+ ScheduledJobEntry sje = (ScheduledJobEntry) jobList.get(i);
+
+ if (desiredExecutionTime < sje.desiredExecutionTime) {
+ break;
+ }
+ }
+ jobList.add(i, newSJE);
+ // if the jobList was empty, then notify the scheduler thread
+ if (i == 0) {
+ this.notifyAll();
+ }
+ }
+
+ /**
+ * Shut down scheduler.
+ */
+ public synchronized void shutdown() {
+ shutdown = true;
+ }
+
+ /**
+ * Run scheduler.
+ */
+ public synchronized void run() {
+ while (!shutdown) {
+ if (jobList.isEmpty()) {
+ linger();
+ } else {
+ ScheduledJobEntry sje = (ScheduledJobEntry) jobList.get(0);
+ long now = System.currentTimeMillis();
+ if (now >= sje.desiredExecutionTime) {
+ executeInABox(sje.job);
+ jobList.remove(0);
+ if (sje.period > 0) {
+ sje.desiredExecutionTime = now + sje.period;
+ schedule(sje);
+ }
+ } else {
+ linger(sje.desiredExecutionTime - now);
+ }
+ }
+ }
+ // clear out the job list to facilitate garbage collection
+ jobList.clear();
+ jobList = null;
+ System.out.println("Leaving scheduler run method");
+ }
+
+ /**
+ * We do not want a single failure to affect the whole scheduler.
+ * @param job job to execute.
+ */
+ void executeInABox(final Job job) {
+ try {
+ job.execute();
+ } catch (Exception e) {
+ System.err.println("The execution of the job threw an exception");
+ e.printStackTrace(System.err);
+ }
+ }
+
+ /**
+ * Wait for notification.
+ */
+ void linger() {
+ try {
+ while (jobList.isEmpty() && !shutdown) {
+ this.wait();
+ }
+ } catch (InterruptedException ie) {
+ shutdown = true;
+ }
+ }
+
+ /**
+ * Wait for notification or time to elapse.
+ * @param timeToLinger time to linger.
+ */
+ void linger(final long timeToLinger) {
+ try {
+ this.wait(timeToLinger);
+ } catch (InterruptedException ie) {
+ shutdown = true;
+ }
+ }
+
+ /**
+ * Represents an entry in job scheduler.
+ */
+ static final class ScheduledJobEntry {
+ /**
+ * Desired execution time.
+ */
+ long desiredExecutionTime;
+ /**
+ * Job to run.
+ */
+ Job job;
+ /**
+ * Repeat period.
+ */
+ long period = 0;
+
+ /**
+ * Create new instance.
+ * @param job job
+ * @param desiredTime desired time.
+ */
+ ScheduledJobEntry(final Job job, final long desiredTime) {
+ this(job, desiredTime, 0);
+ }
+
+ /**
+ * Create new instance.
+ * @param job job
+ * @param desiredTime desired time
+ * @param period repeat period
+ */
+ ScheduledJobEntry(final Job job,
+ final long desiredTime,
+ final long period) {
+ super();
+ this.desiredExecutionTime = desiredTime;
+ this.job = job;
+ this.period = period;
+ }
+ }
+
+}
+
+
