/*
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */
package org.apache.http.impl.conn;

import java.io.Closeable;
import java.io.IOException;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicBoolean;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.http.HttpClientConnection;
import org.apache.http.HttpHost;
import org.apache.http.annotation.Contract;
import org.apache.http.annotation.ThreadingBehavior;
import org.apache.http.config.ConnectionConfig;
import org.apache.http.config.Lookup;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.config.SocketConfig;
import org.apache.http.conn.ConnectionPoolTimeoutException;
import org.apache.http.conn.ConnectionRequest;
import org.apache.http.conn.DnsResolver;
import org.apache.http.conn.HttpClientConnectionManager;
import org.apache.http.conn.HttpClientConnectionOperator;
import org.apache.http.conn.HttpConnectionFactory;
import org.apache.http.conn.ManagedHttpClientConnection;
import org.apache.http.conn.SchemePortResolver;
import org.apache.http.conn.routing.HttpRoute;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.pool.ConnFactory;
import org.apache.http.pool.ConnPoolControl;
import org.apache.http.pool.PoolEntryCallback;
import org.apache.http.pool.PoolStats;
import org.apache.http.protocol.HttpContext;
import org.apache.http.util.Args;
import org.apache.http.util.Asserts;

ClientConnectionPoolManager maintains a pool of HttpClientConnections and is able to service connection requests from multiple execution threads. Connections are pooled on a per route basis. A request for a route which already the manager has persistent connections for available in the pool will be services by leasing a connection from the pool rather than creating a brand new connection. 
 ClientConnectionPoolManager maintains a maximum limit of connection on a per route basis and in total. Per default this implementation will create no more than than 2 concurrent connections per given route and no more 20 connections in total. For many real-world applications these limits may prove too constraining, especially if they use HTTP as a transport protocol for their services. Connection limits, however, can be adjusted using ConnPoolControl methods. 

Total time to live (TTL) set at construction time defines maximum life span
of persistent connections regardless of their expiration setting. No persistent
connection will be re-used past its TTL value.


The handling of stale connections was changed in version 4.4.
Previously, the code would check every connection by default before re-using it.
The code now only checks the connection if the elapsed time since
the last use of the connection exceeds the timeout that has been set.
The default timeout is set to 2000ms

Since:
4.3/**
 * {@code ClientConnectionPoolManager} maintains a pool of
 * {@link HttpClientConnection}s and is able to service connection requests
 * from multiple execution threads. Connections are pooled on a per route
 * basis. A request for a route which already the manager has persistent
 * connections for available in the pool will be services by leasing
 * a connection from the pool rather than creating a brand new connection.
 * <p>
 * {@code ClientConnectionPoolManager} maintains a maximum limit of connection
 * on a per route basis and in total. Per default this implementation will
 * create no more than than 2 concurrent connections per given route
 * and no more 20 connections in total. For many real-world applications
 * these limits may prove too constraining, especially if they use HTTP
 * as a transport protocol for their services. Connection limits, however,
 * can be adjusted using {@link ConnPoolControl} methods.
 * </p>
 * <p>
 * Total time to live (TTL) set at construction time defines maximum life span
 * of persistent connections regardless of their expiration setting. No persistent
 * connection will be re-used past its TTL value.
 * </p>
 * <p>
 * The handling of stale connections was changed in version 4.4.
 * Previously, the code would check every connection by default before re-using it.
 * The code now only checks the connection if the elapsed time since
 * the last use of the connection exceeds the timeout that has been set.
 * The default timeout is set to 2000ms
 * </p>
 *
 * @since 4.3
 */
@Contract(threading = ThreadingBehavior.SAFE_CONDITIONAL)
public class PoolingHttpClientConnectionManager
    implements HttpClientConnectionManager, ConnPoolControl<HttpRoute>, Closeable {

    private final Log log = LogFactory.getLog(getClass());

    private final ConfigData configData;
    private final CPool pool;
    private final HttpClientConnectionOperator connectionOperator;
    private final AtomicBoolean isShutDown;

    private static Registry<ConnectionSocketFactory> getDefaultRegistry() {
        return RegistryBuilder.<ConnectionSocketFactory>create()
                .register("http", PlainConnectionSocketFactory.getSocketFactory())
                .register("https", SSLConnectionSocketFactory.getSocketFactory())
                .build();
    }

    public PoolingHttpClientConnectionManager() {
        this(getDefaultRegistry());
    }

    public PoolingHttpClientConnectionManager(final long timeToLive, final TimeUnit timeUnit) {
        this(getDefaultRegistry(), null, null ,null, timeToLive, timeUnit);
    }

    public PoolingHttpClientConnectionManager(
            final Registry<ConnectionSocketFactory> socketFactoryRegistry) {
        this(socketFactoryRegistry, null, null);
    }

    public PoolingHttpClientConnectionManager(
            final Registry<ConnectionSocketFactory> socketFactoryRegistry,
            final DnsResolver dnsResolver) {
        this(socketFactoryRegistry, null, dnsResolver);
    }

    public PoolingHttpClientConnectionManager(
            final Registry<ConnectionSocketFactory> socketFactoryRegistry,
            final HttpConnectionFactory<HttpRoute, ManagedHttpClientConnection> connFactory) {
        this(socketFactoryRegistry, connFactory, null);
    }

    public PoolingHttpClientConnectionManager(
            final HttpConnectionFactory<HttpRoute, ManagedHttpClientConnection> connFactory) {
        this(getDefaultRegistry(), connFactory, null);
    }

    public PoolingHttpClientConnectionManager(
            final Registry<ConnectionSocketFactory> socketFactoryRegistry,
            final HttpConnectionFactory<HttpRoute, ManagedHttpClientConnection> connFactory,
            final DnsResolver dnsResolver) {
        this(socketFactoryRegistry, connFactory, null, dnsResolver, -1, TimeUnit.MILLISECONDS);
    }

    public PoolingHttpClientConnectionManager(
            final Registry<ConnectionSocketFactory> socketFactoryRegistry,
            final HttpConnectionFactory<HttpRoute, ManagedHttpClientConnection> connFactory,
            final SchemePortResolver schemePortResolver,
            final DnsResolver dnsResolver,
            final long timeToLive, final TimeUnit timeUnit) {
        this(
            new DefaultHttpClientConnectionOperator(socketFactoryRegistry, schemePortResolver, dnsResolver),
            connFactory,
            timeToLive, timeUnit
        );
    }

    
Since:
4.4/**
     * @since 4.4
     */
    public PoolingHttpClientConnectionManager(
        final HttpClientConnectionOperator httpClientConnectionOperator,
        final HttpConnectionFactory<HttpRoute, ManagedHttpClientConnection> connFactory,
        final long timeToLive, final TimeUnit timeUnit) {
        super();
        this.configData = new ConfigData();
        this.pool = new CPool(new InternalConnectionFactory(
                this.configData, connFactory), 2, 20, timeToLive, timeUnit);
        this.pool.setValidateAfterInactivity(2000);
        this.connectionOperator = Args.notNull(httpClientConnectionOperator, "HttpClientConnectionOperator");
        this.isShutDown = new AtomicBoolean(false);
    }

    
Visible for test.
/**
     * Visible for test.
     */
    PoolingHttpClientConnectionManager(
            final CPool pool,
            final Lookup<ConnectionSocketFactory> socketFactoryRegistry,
            final SchemePortResolver schemePortResolver,
            final DnsResolver dnsResolver) {
        super();
        this.configData = new ConfigData();
        this.pool = pool;
        this.connectionOperator = new DefaultHttpClientConnectionOperator(
                socketFactoryRegistry, schemePortResolver, dnsResolver);
        this.isShutDown = new AtomicBoolean(false);
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            shutdown();
        } finally {
            super.finalize();
        }
    }

    @Override
    public void close() {
        shutdown();
    }

    private String format(final HttpRoute route, final Object state) {
        final StringBuilder buf = new StringBuilder();
        buf.append("[route: ").append(route).append("]");
        if (state != null) {
            buf.append("[state: ").append(state).append("]");
        }
        return buf.toString();
    }

    private String formatStats(final HttpRoute route) {
        final StringBuilder buf = new StringBuilder();
        final PoolStats totals = this.pool.getTotalStats();
        final PoolStats stats = this.pool.getStats(route);
        buf.append("[total kept alive: ").append(totals.getAvailable()).append("; ");
        buf.append("route allocated: ").append(stats.getLeased() + stats.getAvailable());
        buf.append(" of ").append(stats.getMax()).append("; ");
        buf.append("total allocated: ").append(totals.getLeased() + totals.getAvailable());
        buf.append(" of ").append(totals.getMax()).append("]");
        return buf.toString();
    }

    private String format(final CPoolEntry entry) {
        final StringBuilder buf = new StringBuilder();
        buf.append("[id: ").append(entry.getId()).append("]");
        buf.append("[route: ").append(entry.getRoute()).append("]");
        final Object state = entry.getState();
        if (state != null) {
            buf.append("[state: ").append(state).append("]");
        }
        return buf.toString();
    }

    private SocketConfig resolveSocketConfig(final HttpHost host) {
        SocketConfig socketConfig = this.configData.getSocketConfig(host);
        if (socketConfig == null) {
            socketConfig = this.configData.getDefaultSocketConfig();
        }
        if (socketConfig == null) {
            socketConfig = SocketConfig.DEFAULT;
        }
        return socketConfig;
    }

    @Override
    public ConnectionRequest requestConnection(
            final HttpRoute route,
            final Object state) {
        Args.notNull(route, "HTTP route");
        if (this.log.isDebugEnabled()) {
            this.log.debug("Connection request: " + format(route, state) + formatStats(route));
        }
        final Future<CPoolEntry> future = this.pool.lease(route, state, null);
        return new ConnectionRequest() {

            @Override
            public boolean cancel() {
                return future.cancel(true);
            }

            @Override
            public HttpClientConnection get(
                    final long timeout,
                    final TimeUnit timeUnit) throws InterruptedException, ExecutionException, ConnectionPoolTimeoutException {
                final HttpClientConnection conn = leaseConnection(future, timeout, timeUnit);
                if (conn.isOpen()) {
                    final HttpHost host;
                    if (route.getProxyHost() != null) {
                        host = route.getProxyHost();
                    } else {
                        host = route.getTargetHost();
                    }
                    final SocketConfig socketConfig = resolveSocketConfig(host);
                    conn.setSocketTimeout(socketConfig.getSoTimeout());
                }
                return conn;
            }

        };

    }

    protected HttpClientConnection leaseConnection(
            final Future<CPoolEntry> future,
            final long timeout,
            final TimeUnit timeUnit) throws InterruptedException, ExecutionException, ConnectionPoolTimeoutException {
        final CPoolEntry entry;
        try {
            entry = future.get(timeout, timeUnit);
            if (entry == null || future.isCancelled()) {
                throw new ExecutionException(new CancellationException("Operation cancelled"));
            }
            Asserts.check(entry.getConnection() != null, "Pool entry with no connection");
            if (this.log.isDebugEnabled()) {
                this.log.debug("Connection leased: " + format(entry) + formatStats(entry.getRoute()));
            }
            return CPoolProxy.newProxy(entry);
        } catch (final TimeoutException ex) {
            throw new ConnectionPoolTimeoutException("Timeout waiting for connection from pool");
        }
    }

    @Override
    public void releaseConnection(
            final HttpClientConnection managedConn,
            final Object state,
            final long keepalive, final TimeUnit timeUnit) {
        Args.notNull(managedConn, "Managed connection");
        synchronized (managedConn) {
            final CPoolEntry entry = CPoolProxy.detach(managedConn);
            if (entry == null) {
                return;
            }
            final ManagedHttpClientConnection conn = entry.getConnection();
            try {
                if (conn.isOpen()) {
                    final TimeUnit effectiveUnit = timeUnit != null ? timeUnit : TimeUnit.MILLISECONDS;
                    entry.setState(state);
                    entry.updateExpiry(keepalive, effectiveUnit);
                    if (this.log.isDebugEnabled()) {
                        final String s;
                        if (keepalive > 0) {
                            s = "for " + (double) effectiveUnit.toMillis(keepalive) / 1000 + " seconds";
                        } else {
                            s = "indefinitely";
                        }
                        this.log.debug("Connection " + format(entry) + " can be kept alive " + s);
                    }
                    conn.setSocketTimeout(0);
                }
            } finally {
                this.pool.release(entry, conn.isOpen() && entry.isRouteComplete());
                if (this.log.isDebugEnabled()) {
                    this.log.debug("Connection released: " + format(entry) + formatStats(entry.getRoute()));
                }
            }
        }
    }

    @Override
    public void connect(
            final HttpClientConnection managedConn,
            final HttpRoute route,
            final int connectTimeout,
            final HttpContext context) throws IOException {
        Args.notNull(managedConn, "Managed Connection");
        Args.notNull(route, "HTTP route");
        final ManagedHttpClientConnection conn;
        synchronized (managedConn) {
            final CPoolEntry entry = CPoolProxy.getPoolEntry(managedConn);
            conn = entry.getConnection();
        }
        final HttpHost host;
        if (route.getProxyHost() != null) {
            host = route.getProxyHost();
        } else {
            host = route.getTargetHost();
        }
        this.connectionOperator.connect(
                conn, host, route.getLocalSocketAddress(), connectTimeout, resolveSocketConfig(host), context);
    }

    @Override
    public void upgrade(
            final HttpClientConnection managedConn,
            final HttpRoute route,
            final HttpContext context) throws IOException {
        Args.notNull(managedConn, "Managed Connection");
        Args.notNull(route, "HTTP route");
        final ManagedHttpClientConnection conn;
        synchronized (managedConn) {
            final CPoolEntry entry = CPoolProxy.getPoolEntry(managedConn);
            conn = entry.getConnection();
        }
        this.connectionOperator.upgrade(conn, route.getTargetHost(), context);
    }

    @Override
    public void routeComplete(
            final HttpClientConnection managedConn,
            final HttpRoute route,
            final HttpContext context) throws IOException {
        Args.notNull(managedConn, "Managed Connection");
        Args.notNull(route, "HTTP route");
        synchronized (managedConn) {
            final CPoolEntry entry = CPoolProxy.getPoolEntry(managedConn);
            entry.markRouteComplete();
        }
    }

    @Override
    public void shutdown() {
        if (this.isShutDown.compareAndSet(false, true)) {
            this.log.debug("Connection manager is shutting down");
            try {
                this.pool.shutdown();
            } catch (final IOException ex) {
                this.log.debug("I/O exception shutting down connection manager", ex);
            }
            this.log.debug("Connection manager shut down");
        }
    }

    @Override
    public void closeIdleConnections(final long idleTimeout, final TimeUnit timeUnit) {
        if (this.log.isDebugEnabled()) {
            this.log.debug("Closing connections idle longer than " + idleTimeout + " " + timeUnit);
        }
        this.pool.closeIdle(idleTimeout, timeUnit);
    }

    @Override
    public void closeExpiredConnections() {
        this.log.debug("Closing expired connections");
        this.pool.closeExpired();
    }

    protected void enumAvailable(final PoolEntryCallback<HttpRoute, ManagedHttpClientConnection> callback) {
        this.pool.enumAvailable(callback);
    }

    protected void enumLeased(final PoolEntryCallback<HttpRoute, ManagedHttpClientConnection> callback) {
        this.pool.enumLeased(callback);
    }

    @Override
    public int getMaxTotal() {
        return this.pool.getMaxTotal();
    }

    @Override
    public void setMaxTotal(final int max) {
        this.pool.setMaxTotal(max);
    }

    @Override
    public int getDefaultMaxPerRoute() {
        return this.pool.getDefaultMaxPerRoute();
    }

    @Override
    public void setDefaultMaxPerRoute(final int max) {
        this.pool.setDefaultMaxPerRoute(max);
    }

    @Override
    public int getMaxPerRoute(final HttpRoute route) {
        return this.pool.getMaxPerRoute(route);
    }

    @Override
    public void setMaxPerRoute(final HttpRoute route, final int max) {
        this.pool.setMaxPerRoute(route, max);
    }

    @Override
    public PoolStats getTotalStats() {
        return this.pool.getTotalStats();
    }

    @Override
    public PoolStats getStats(final HttpRoute route) {
        return this.pool.getStats(route);
    }

    
Since:
4.4/**
     * @since 4.4
     */
    public Set<HttpRoute> getRoutes() {
        return this.pool.getRoutes();
    }

    public SocketConfig getDefaultSocketConfig() {
        return this.configData.getDefaultSocketConfig();
    }

    public void setDefaultSocketConfig(final SocketConfig defaultSocketConfig) {
        this.configData.setDefaultSocketConfig(defaultSocketConfig);
    }

    public ConnectionConfig getDefaultConnectionConfig() {
        return this.configData.getDefaultConnectionConfig();
    }

    public void setDefaultConnectionConfig(final ConnectionConfig defaultConnectionConfig) {
        this.configData.setDefaultConnectionConfig(defaultConnectionConfig);
    }

    public SocketConfig getSocketConfig(final HttpHost host) {
        return this.configData.getSocketConfig(host);
    }

    public void setSocketConfig(final HttpHost host, final SocketConfig socketConfig) {
        this.configData.setSocketConfig(host, socketConfig);
    }

    public ConnectionConfig getConnectionConfig(final HttpHost host) {
        return this.configData.getConnectionConfig(host);
    }

    public void setConnectionConfig(final HttpHost host, final ConnectionConfig connectionConfig) {
        this.configData.setConnectionConfig(host, connectionConfig);
    }

    
See Also:
setValidateAfterInactivity(int)
Since:
4.4/**
     * @see #setValidateAfterInactivity(int)
     *
     * @since 4.4
     */
    public int getValidateAfterInactivity() {
        return pool.getValidateAfterInactivity();
    }

    
Defines period of inactivity in milliseconds after which persistent connections must be re-validated prior to being leased to the consumer. Non-positive value passed to this method disables connection validation. This check helps detect connections that have become stale (half-closed) while kept inactive in the pool. 
See Also:
leaseConnection(Future<CPoolEntry>, long, TimeUnit)
Since:
4.4/**
     * Defines period of inactivity in milliseconds after which persistent connections must
     * be re-validated prior to being {@link #leaseConnection(java.util.concurrent.Future,
     *   long, java.util.concurrent.TimeUnit) leased} to the consumer. Non-positive value passed
     * to this method disables connection validation. This check helps detect connections
     * that have become stale (half-closed) while kept inactive in the pool.
     *
     * @see #leaseConnection(java.util.concurrent.Future, long, java.util.concurrent.TimeUnit)
     *
     * @since 4.4
     */
    public void setValidateAfterInactivity(final int ms) {
        pool.setValidateAfterInactivity(ms);
    }

    static class ConfigData {

        private final Map<HttpHost, SocketConfig> socketConfigMap;
        private final Map<HttpHost, ConnectionConfig> connectionConfigMap;
        private volatile SocketConfig defaultSocketConfig;
        private volatile ConnectionConfig defaultConnectionConfig;

        ConfigData() {
            super();
            this.socketConfigMap = new ConcurrentHashMap<HttpHost, SocketConfig>();
            this.connectionConfigMap = new ConcurrentHashMap<HttpHost, ConnectionConfig>();
        }

        public SocketConfig getDefaultSocketConfig() {
            return this.defaultSocketConfig;
        }

        public void setDefaultSocketConfig(final SocketConfig defaultSocketConfig) {
            this.defaultSocketConfig = defaultSocketConfig;
        }

        public ConnectionConfig getDefaultConnectionConfig() {
            return this.defaultConnectionConfig;
        }

        public void setDefaultConnectionConfig(final ConnectionConfig defaultConnectionConfig) {
            this.defaultConnectionConfig = defaultConnectionConfig;
        }

        public SocketConfig getSocketConfig(final HttpHost host) {
            return this.socketConfigMap.get(host);
        }

        public void setSocketConfig(final HttpHost host, final SocketConfig socketConfig) {
            this.socketConfigMap.put(host, socketConfig);
        }

        public ConnectionConfig getConnectionConfig(final HttpHost host) {
            return this.connectionConfigMap.get(host);
        }

        public void setConnectionConfig(final HttpHost host, final ConnectionConfig connectionConfig) {
            this.connectionConfigMap.put(host, connectionConfig);
        }

    }

    static class InternalConnectionFactory implements ConnFactory<HttpRoute, ManagedHttpClientConnection> {

        private final ConfigData configData;
        private final HttpConnectionFactory<HttpRoute, ManagedHttpClientConnection> connFactory;

        InternalConnectionFactory(
                final ConfigData configData,
                final HttpConnectionFactory<HttpRoute, ManagedHttpClientConnection> connFactory) {
            super();
            this.configData = configData != null ? configData : new ConfigData();
            this.connFactory = connFactory != null ? connFactory :
                ManagedHttpClientConnectionFactory.INSTANCE;
        }

        @Override
        public ManagedHttpClientConnection create(final HttpRoute route) throws IOException {
            ConnectionConfig config = null;
            if (route.getProxyHost() != null) {
                config = this.configData.getConnectionConfig(route.getProxyHost());
            }
            if (config == null) {
                config = this.configData.getConnectionConfig(route.getTargetHost());
            }
            if (config == null) {
                config = this.configData.getDefaultConnectionConfig();
            }
            if (config == null) {
                config = ConnectionConfig.DEFAULT;
            }
            return this.connFactory.create(route, config);
        }

    }

}