org.taverna.server.master.notification.RateLimitedDispatcher.java Source code

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Here is the source code for org.taverna.server.master.notification.RateLimitedDispatcher.java

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/*
 * Copyright (C) 2011 The University of Manchester
 * 
 * See the file "LICENSE.txt" for license terms.
 */
package org.taverna.server.master.notification;

import java.util.HashMap;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.joda.time.DateTime;
import org.taverna.server.master.interfaces.MessageDispatcher;
import org.taverna.server.master.interfaces.TavernaRun;

/**
 * Rate-limiting support. Some message fabrics simply should not be used to send
 * a lot of messages.
 * 
 * @author Donal Fellows
 */
public abstract class RateLimitedDispatcher implements MessageDispatcher {
    /** Pre-configured logger. */
    protected Log log = LogFactory.getLog("Taverna.Server.Notification");
    private int cooldownSeconds;
    private Map<String, DateTime> lastSend = new HashMap<String, DateTime>();

    String valid(String value, String def) {
        if (value == null || value.trim().isEmpty() || value.trim().startsWith("${"))
            return def;
        else
            return value.trim();
    }

    /**
     * Set how long must elapse between updates to the status of any particular
     * user. Calls before that time are just silently dropped.
     * 
     * @param cooldownSeconds
     *            Time to elapse, in seconds.
     */
    public void setCooldownSeconds(int cooldownSeconds) {
        this.cooldownSeconds = cooldownSeconds;
    }

    /**
     * Test whether the rate limiter allows the given user to send a message.
     * 
     * @param who
     *            Who wants to send the message?
     * @return <tt>true</tt> iff they are permitted.
     */
    protected boolean isSendAllowed(String who) {
        DateTime now = new DateTime();
        synchronized (lastSend) {
            DateTime last = lastSend.get(who);
            if (last != null) {
                if (!now.isAfter(last.plusSeconds(cooldownSeconds)))
                    return false;
            }
            lastSend.put(who, now);
        }
        return true;
    }

    @Override
    public void dispatch(TavernaRun ignored, String messageSubject, String messageContent, String target)
            throws Exception {
        if (isSendAllowed(target))
            dispatch(messageSubject, messageContent, target);
    }

    /**
     * Dispatch a message to a recipient that doesn't care what produced it.
     * 
     * @param messageSubject
     *            The subject of the message to send.
     * @param messageContent
     *            The plain-text content of the message to send.
     * @param target
     *            A description of where it is to go.
     * @throws Exception
     *             If anything goes wrong.
     */
    public abstract void dispatch(String messageSubject, String messageContent, String target) throws Exception;
}