// Copyright 2012 Citrix Systems, Inc. Licensed under the
// Apache License, Version 2.0 (the "License"); you may not use this
// file except in compliance with the License. Citrix Systems, Inc.
// reserves all rights not expressly granted by 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.
//
// Automatically generated by addcopyright.py at 04/03/2012
package com.cloud.vm;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import org.apache.log4j.Logger;
import com.cloud.cluster.StackMaid;
import com.cloud.utils.Pair;
import com.cloud.utils.concurrency.NamedThreadFactory;
import com.cloud.utils.db.GlobalLock;
import com.cloud.utils.db.Transaction;
//
// TODO: simple load scanner, to minimize code changes required in console proxy manager and SSVM, we still leave most of work at handler
//
public class SystemVmLoadScanner<T> {
public enum AfterScanAction { nop, expand, shrink }
private static final Logger s_logger = Logger.getLogger(SystemVmLoadScanner.class);
private static final int ACQUIRE_GLOBAL_LOCK_TIMEOUT_FOR_COOPERATION = 3; // 3 seconds
private final SystemVmLoadScanHandler<T> _scanHandler;
private final ScheduledExecutorService _capacityScanScheduler;
private final GlobalLock _capacityScanLock;
public SystemVmLoadScanner(SystemVmLoadScanHandler<T> scanHandler) {
_scanHandler = scanHandler;
_capacityScanScheduler = Executors.newScheduledThreadPool(1, new NamedThreadFactory(scanHandler.getScanHandlerName()));
_capacityScanLock = GlobalLock.getInternLock(scanHandler.getScanHandlerName() + ".scan.lock");
}
public void initScan(long startupDelayMs, long scanIntervalMs) {
_capacityScanScheduler.scheduleAtFixedRate(getCapacityScanTask(), startupDelayMs, scanIntervalMs, TimeUnit.MILLISECONDS);
}
public void stop() {
_capacityScanScheduler.shutdownNow();
try {
_capacityScanScheduler.awaitTermination(1000, TimeUnit.MILLISECONDS);
} catch (InterruptedException e) {
}
_capacityScanLock.releaseRef();
}
private Runnable getCapacityScanTask() {
return new Runnable() {
@Override
public void run() {
Transaction txn = Transaction.open(Transaction.CLOUD_DB);
try {
reallyRun();
} catch (Throwable e) {
s_logger.warn("Unexpected exception " + e.getMessage(), e);
} finally {
StackMaid.current().exitCleanup();
txn.close();
}
}
private void reallyRun() {
loadScan();
}
};
}
private void loadScan() {
if(!_scanHandler.canScan()) {
return;
}
if (!_capacityScanLock.lock(ACQUIRE_GLOBAL_LOCK_TIMEOUT_FOR_COOPERATION)) {
if (s_logger.isTraceEnabled()) {
s_logger.trace("Capacity scan lock is used by others, skip and wait for my turn");
}
return;
}
try {
_scanHandler.onScanStart();
T[] pools = _scanHandler.getScannablePools();
for(T p : pools) {
if(_scanHandler.isPoolReadyForScan(p)) {
Pair<AfterScanAction, Object> actionInfo = _scanHandler.scanPool(p);
switch(actionInfo.first()) {
case nop:
break;
case expand:
_scanHandler.expandPool(p, actionInfo.second());
break;
case shrink:
_scanHandler.shrinkPool(p, actionInfo.second());
break;
}
}
}
_scanHandler.onScanEnd();
} finally {
_capacityScanLock.unlock();
}
}
}