/* This file is part of VoltDB.
* Copyright (C) 2008-2014 VoltDB Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
package txnIdSelfCheck;
import java.util.HashMap;
import java.util.Map.Entry;
import java.util.concurrent.Semaphore;
/**
* A very naive rate limiter for txnId-selfcheck2.
*
* The rate limiter creates a semaphore for each type of transactions. The
* semaphore is initialized with permits proportional to the given ratio of the
* total permits. Each second, the owner can call resetPermits() to reset the
* permits of each type back to the initial values.
*/
public class TxnId2RateLimiter {
private final HashMap<Integer, Semaphore> m_permits =
new HashMap<Integer, Semaphore>();
private final HashMap<Integer, Integer> m_initialPermits =
new HashMap<Integer, Integer>();
private final long m_totalPermits;
// last time permits were reset
private long m_lastPermitResetTs = System.currentTimeMillis();
public TxnId2RateLimiter(long totalPermits) {
m_totalPermits = totalPermits;
}
/**
* @param type type of invocation.
* @param ratio ratio of permits in total permits for this type. 0 <= ratio <= 1.
*/
public Semaphore addType(int type, double ratio) {
Semaphore permits = new Semaphore((int) (m_totalPermits * ratio));
m_permits.put(type, permits);
m_initialPermits.put(type, permits.availablePermits());
return permits;
}
public void resetPermits() {
for (Entry<Integer, Semaphore> e : m_permits.entrySet()) {
int type = e.getKey();
Semaphore permits = e.getValue();
permits.drainPermits();
permits.release(m_initialPermits.get(type));
}
}
/**
* Updates the permits every second.
*
* Caller can call this method many times in a second, it will only update
* the permits when a second has passed.
*/
public void updateActivePermits(final long ts) {
// Reset the permits roughly every second
if (ts - m_lastPermitResetTs > 1000) {
resetPermits();
m_lastPermitResetTs = ts;
}
}
}