package com.netflix.astyanax.connectionpool.impl;
import java.util.Iterator;
import java.util.List;
import com.google.common.collect.Lists;
import com.netflix.astyanax.connectionpool.Connection;
import com.netflix.astyanax.connectionpool.ConnectionPoolConfiguration;
import com.netflix.astyanax.connectionpool.ConnectionPoolMonitor;
import com.netflix.astyanax.connectionpool.HostConnectionPool;
import com.netflix.astyanax.connectionpool.Operation;
import com.netflix.astyanax.connectionpool.exceptions.ConnectionException;
import com.netflix.astyanax.connectionpool.exceptions.NoAvailableHostsException;
/**
* Finds the {@link HostConnectionPool} with the max idle connections when borrowing a connection from the pool.
* This execute with failover impl is used within the {@link TokenAwareConnectionPoolImpl} class depending on the configured
* {@link HostSelectorStrategy}
*
* @author elandau
*
* @param <CL>
* @param <R>
*
* @see {@link TokenAwareConnectionPoolImpl#executeWithFailover(Operation, com.netflix.astyanax.retry.RetryPolicy)} for details on where this class is referenced
*/
public class LeastOutstandingExecuteWithFailover<CL, R> extends AbstractExecuteWithFailoverImpl<CL, R> {
protected HostConnectionPool<CL> pool;
private int retryCountdown;
protected final List<HostConnectionPool<CL>> pools;
protected int waitDelta;
protected int waitMultiplier = 1;
public LeastOutstandingExecuteWithFailover(ConnectionPoolConfiguration config, ConnectionPoolMonitor monitor,
List<HostConnectionPool<CL>> pools) throws ConnectionException {
super(config, monitor);
this.pools = Lists.newArrayList(pools);
if (this.pools == null || this.pools.isEmpty()) {
throw new NoAvailableHostsException("No hosts to borrow from");
}
int size = this.pools.size();
retryCountdown = Math.min(config.getMaxFailoverCount(), size);
if (retryCountdown < 0)
retryCountdown = size;
else if (retryCountdown == 0)
retryCountdown = 1;
waitDelta = config.getMaxTimeoutWhenExhausted() / retryCountdown;
}
public boolean canRetry() {
return --retryCountdown > 0;
}
@Override
public HostConnectionPool<CL> getCurrentHostConnectionPool() {
return pool;
}
@Override
public Connection<CL> borrowConnection(Operation<CL, R> operation) throws ConnectionException {
// find the pool with the least outstanding (i.e most idle) active connections
Iterator<HostConnectionPool<CL>> iterator = this.pools.iterator();
HostConnectionPool eligible = iterator.next();
while (iterator.hasNext()) {
HostConnectionPool<CL> candidate = iterator.next();
if (candidate.getIdleConnectionCount() > eligible.getIdleConnectionCount()) {
eligible = candidate;
}
}
return eligible.borrowConnection(waitDelta * waitMultiplier);
}
}