Collector.java

/*
 * Collector.java
 * Copyright (C) 2011,2012 Wannes De Smet
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.xenmaster.monitoring.engine;

import com.lmax.disruptor.EventHandler;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.PriorityQueue;
import org.apache.log4j.Logger;
import org.xenmaster.api.entity.Host;
import org.xenmaster.controller.BadAPICallException;
import org.xenmaster.monitoring.data.RRD;
import org.xenmaster.monitoring.data.RRDUpdates;
import org.xenmaster.monitoring.data.Record;

/**
 *
 * @created Oct 14, 2011
 *
 * @author double-u
 */
public class Collector implements EventHandler<Record> {

    protected long lastUpdate;
    protected static PriorityQueue<Slot> slots = new PriorityQueue<>();

    public void boot() {
        createConnections();
    }

    /**
     * Do not, under *any* circumstance, put this into the ctor. It will
     * recursively create CachingFacilities
     */
    private void createConnections() {
        ArrayList<Slot> newSlots = new ArrayList<>();
        Slot[] current = slots.toArray(new Slot[slots.size()]);
        try {
            for (Host h : Host.getAll()) {
                newSlots.add(new Slot(h));
            }
        } catch (BadAPICallException ex) {
            Logger.getLogger(getClass()).error("Failed to get all hosts", ex);
        }

        slots.clear();

        // We want to retain existing connections, remove all that aren't present in the newSlots
        for (Slot ns : newSlots) {
            boolean newSlot = true;

            for (int i = 0; i < current.length; i++) {
                if (current[i].equals(ns)) {

                    // If it matches, re-add the current one
                    newSlot = false;
                    slots.add(current[i]);
                    break;
                }
            }

            if (newSlot) {
                slots.add(ns);
            }
        }
    }

    public static abstract class TimingProvider implements Runnable {

        private int loopCount;
        private static int TIMESPAN = 2000;
        private long lastTime;

        protected final Slot getNextSlot() {
            boolean gotWorkToDo = false;
            Slot slot = null;

            while (!gotWorkToDo) {
                if (loopCount > 200 && System.currentTimeMillis() - lastTime < TIMESPAN) {
                    // We've spun over 200 times in less then 2 seconds, indicating slot handling has crashed
                    throw new IllegalStateException("Slot handling is defective");
                } else if (System.currentTimeMillis() - lastTime >= TIMESPAN) {
                    loopCount = 0;
                }
                
                lastTime = System.currentTimeMillis();
                slot = slots.peek();
                if (slot == null) {
                    Logger.getLogger(getClass()).warn("No server slots available. Exiting ...");
                    return null;
                }

                // Wait until 5 seconds have passed
                long delta = System.currentTimeMillis() - slot.lastPolled;
                // Sleep when all slots have been updated in less then 5 seconds,
                // or if they are being processed or unstable
                if (delta < 5000 || slot.isBeingProcessed() || !slot.isStable()) {
                    try {
                        long sleepyTime = 5000 - delta;

                        if (Math.signum(sleepyTime) != 1.0) {
                            Thread.sleep(5000);
                        } else {
                            Thread.sleep(sleepyTime);
                        }


                    } catch (InterruptedException ex) {
                        Logger.getLogger(getClass()).error("Failed to catch a shut-eye", ex);
                    }
                }

                if (!slot.isBeingProcessed() && slot.startProcessing()) {
                    gotWorkToDo = true;
                }

                loopCount++;
            }
            return slot;
        }
    }

    @Override
    public void onEvent(Record t, long l, boolean bln) throws Exception {
        Slot slot = slots.peek();
        if (slot == null || !slot.isBeingProcessed()) {
            return;
        }

        if (slot.isUpdate()) {
            URLConnection connection = slot.getConnection();
            if (connection == null) {
                slot.errorOccurred();
            } else {
                RRDUpdates updates = RRDUpdates.parse(connection.getInputStream());

                if (updates != null) {
                    t.addLatestData(updates);
                } else {
                    slot.errorOccurred();
                }
            }

        } else {
            t.setInitialData(RRD.parse(slot.getConnection().getInputStream()));
        }
        slot.processingDone();
    }
}