SocketPool encapsulates the list of PooledSockets against one specific host, and contains methods for acquiring or returning PooledSockets. : Socket Connection « Network « C# / C Sharp

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C# / C Sharp » Network » Socket ConnectionScreenshots 
SocketPool encapsulates the list of PooledSockets against one specific host, and contains methods for acquiring or returning PooledSockets.
 

//Copyright (c) 2007-2008 Henrik Schröder, Oliver Kofoed Pedersen

//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 OR COPYRIGHT
//HOLDERS 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.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Net;
using System.Text;
using System.Net.Sockets;
using System.Threading;

namespace Apollo.Common.Cache
{
    /// <summary>
    /// The PooledSocket class encapsulates a socket connection to a specified memcached server.
    /// It contains a buffered stream for communication, and methods for sending and retrieving
    /// data from the memcached server, as well as general memcached error checking.
    /// </summary>


    internal delegate T UseSocket<T>(PooledSocket socket);
    internal delegate void UseSocket(PooledSocket socket);
    /// <summary>
    /// The PooledSocket class encapsulates a socket connection to a specified memcached server.
    /// It contains a buffered stream for communication, and methods for sending and retrieving
    /// data from the memcached server, as well as general memcached error checking.
    /// </summary>
    internal class PooledSocket : IDisposable
    {

        private SocketPool socketPool;
        private Socket socket;
        private Stream stream;
        public readonly DateTime Created;

        public PooledSocket(SocketPool socketPool, IPEndPoint endPoint, int sendReceiveTimeout)
        {
            this.socketPool = socketPool;
            Created = DateTime.Now;

            //Set up the socket.
            socket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
            socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.SendTimeout, sendReceiveTimeout);
            socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, sendReceiveTimeout);
            socket.ReceiveTimeout = sendReceiveTimeout;
            socket.SendTimeout = sendReceiveTimeout;

            //Do not use Nagle's Algorithm
            socket.NoDelay = true;

            //Establish connection
            socket.Connect(endPoint);

            //Wraps two layers of streams around the socket for communication.
            stream = new BufferedStream(new NetworkStream(socket, false));
        }

        /// <summary>
        /// Disposing of a PooledSocket object in any way causes it to be returned to its SocketPool.
        /// </summary>
        public void Dispose()
        {
            socketPool.Return(this);
        }

        /// <summary>
        /// This method closes the underlying stream and socket.
        /// </summary>
        public void Close()
        {
            if (stream != null)
            {
                try stream.Close()}
                catch (Exception e)
                {
                    Console.WriteLine("Error closing stream: " + socketPool.Host);
                }
                stream = null;
            }
            if (socket != null)
            {
                try socket.Shutdown(SocketShutdown.Both)}
                catch (Exception e)
                {
                    Console.WriteLine("Error shutting down socket: " + socketPool.Host);
                }
                try socket.Close()}
                catch (Exception e)
                {
                    Console.WriteLine("Error closing socket: " + socketPool.Host);
                }
                socket = null;
            }
        }

        /// <summary>
        /// Checks if the underlying socket and stream is connected and available.
        /// </summary>
        public bool IsAlive
        {
            get return socket != null && socket.Connected && stream.CanRead; }
        }

        /// <summary>
        /// Writes a string to the socket encoded in UTF8 format.
        /// </summary>
        public void Write(string str)
        {
            Write(Encoding.UTF8.GetBytes(str));
        }

        /// <summary>
        /// Writes an array of bytes to the socket and flushes the stream.
        /// </summary>
        public void Write(byte[] bytes)
        {
            stream.Write(bytes, 0, bytes.Length);
            stream.Flush();
        }

        /// <summary>
        /// Reads from the socket until the sequence '\r\n' is encountered, 
        /// and returns everything up to but not including that sequence as a UTF8-encoded string
        /// </summary>
        public string ReadLine()
        {
            MemoryStream buffer = new MemoryStream();
            int b;
            bool gotReturn = false;
            while ((b = stream.ReadByte()) != -1)
            {
                if (gotReturn)
                {
                    if (b == 10)
                    {
                        break;
                    }
                    else
                    {
                        buffer.WriteByte(13);
                        gotReturn = false;
                    }
                }
                if (b == 13)
                {
                    gotReturn = true;
                }
                else
                {
                    buffer.WriteByte((byte)b);
                }
            }
            return Encoding.UTF8.GetString(buffer.GetBuffer());
        }

        /// <summary>
        /// Reads a response line from the socket, checks for general memcached errors, and returns the line.
        /// If an error is encountered, this method will throw an exception.
        /// </summary>
        public string ReadResponse()
        {
            string response = ReadLine();

            if (String.IsNullOrEmpty(response))
            {
                throw new Exception("Received empty response.");
            }

            if (response.StartsWith("ERROR")
                || response.StartsWith("CLIENT_ERROR")
                || response.StartsWith("SERVER_ERROR"))
            {
                throw new Exception("Server returned " + response);
            }

            return response;
        }

        /// <summary>
        /// Fills the given byte array with data from the socket.
        /// </summary>
        public void Read(byte[] bytes)
        {
            if (bytes == null)
            {
                return;
            }

            int readBytes = 0;
            while (readBytes < bytes.Length)
            {
                readBytes += stream.Read(bytes, readBytes, (bytes.Length - readBytes));
            }
        }

        /// <summary>
        /// Reads from the socket until the sequence '\r\n' is encountered.
        /// </summary>
        public void SkipUntilEndOfLine()
        {
            int b;
            bool gotReturn = false;
            while ((b = stream.ReadByte()) != -1)
            {
                if (gotReturn)
                {
                    if (b == 10)
                    {
                        break;
                    }
                    else
                    {
                        gotReturn = false;
                    }
                }
                if (b == 13)
                {
                    gotReturn = true;
                }
            }
        }

        /// <summary>
        /// Resets this PooledSocket by making sure the incoming buffer of the socket is empty.
        /// If there was any leftover data, this method return true.
        /// </summary>
        public bool Reset()
        {
            if (socket.Available > 0)
            {
                byte[] b = new byte[socket.Available];
                Read(b);
                return true;
            }
            return false;
        }
    }

    /// <summary>
    /// The ServerPool encapsulates a collection of memcached servers and the associated SocketPool objects.
    /// This class contains the server-selection logic, and contains methods for executing a block of code on 
    /// a socket from the server corresponding to a given key.
    /// </summary>
    internal class ServerPool
    {
        //Expose the socket pools.
        private SocketPool[] hostList;
        internal SocketPool[] HostList get return hostList; } }

        private Dictionary<uint, SocketPool> hostDictionary;
        private uint[] hostKeys;

        //Internal configuration properties
        private int sendReceiveTimeout = 2000;
        private uint maxPoolSize = 10;
        private uint minPoolSize = 5;
        private TimeSpan socketRecycleAge = TimeSpan.FromMinutes(30);
        internal int SendReceiveTimeout get return sendReceiveTimeout; set sendReceiveTimeout = value; } }
        internal uint MaxPoolSize get return maxPoolSize; set maxPoolSize = value; } }
        internal uint MinPoolSize get return minPoolSize; set minPoolSize = value; } }
        internal TimeSpan SocketRecycleAge get return socketRecycleAge; set socketRecycleAge = value; } }

        /// <summary>
        /// Internal constructor. This method takes the array of hosts and sets up an internal list of socketpools.
        /// </summary>
        internal ServerPool(string[] hosts)
        {
            hostDictionary = new Dictionary<uint, SocketPool>();
            List<SocketPool> pools = new List<SocketPool>();
            List<uint> keys = new List<uint>();
            foreach (string host in hosts)
            {
                //Create pool
                SocketPool pool = new SocketPool(this, host.Trim());

                //Create 250 keys for this pool, store each key in the hostDictionary, as well as in the list of keys.
                for (int i = 0; i < 250; i++)
                {
                    uint key = (uint)i;
                    if (!hostDictionary.ContainsKey(key))
                    {
                        hostDictionary[key= pool;
                        keys.Add(key);
                    }
                }

                pools.Add(pool);
            }

            //Hostlist should contain the list of all pools that has been created.
            hostList = pools.ToArray();

            //Hostkeys should contain the list of all key for all pools that have been created.
            //This array forms the server key continuum that we use to lookup which server a
            //given item key hash should be assigned to.
            keys.Sort();
            hostKeys = keys.ToArray();
        }

        /// <summary>
        /// Given an item key hash, this method returns the serverpool which is closest on the server key continuum.
        /// </summary>
        internal SocketPool GetSocketPool(uint hash)
        {
            //Quick return if we only have one host.
            if (hostList.Length == 1)
            {
                return hostList[0];
            }

            //New "ketama" host selection.
            int i = Array.BinarySearch(hostKeys, hash);

            //If not exact match...
            if (i < 0)
            {
                //Get the index of the first item bigger than the one searched for.
                i = ~i;

                //If i is bigger than the last index, it was bigger than the last item = use the first item.
                if (i >= hostKeys.Length)
                {
                    i = 0;
                }
            }
            return hostDictionary[hostKeys[i]];
        }

        internal SocketPool GetSocketPool(string host)
        {
            return Array.Find(HostList, delegate(SocketPool socketPool) { return socketPool.Host == host; });
        }

        /// <summary>
        /// This method executes the given delegate on a socket from the server that corresponds to the given hash.
        /// If anything causes an error, the given defaultValue will be returned instead.
        /// This method takes care of disposing the socket properly once the delegate has executed.
        /// </summary>
        internal T Execute<T>(uint hash, T defaultValue, UseSocket<T> use)
        {
            return Execute(GetSocketPool(hash), defaultValue, use);
        }

        internal T Execute<T>(SocketPool pool, T defaultValue, UseSocket<T> use)
        {
            PooledSocket sock = null;
            try
            {
                //Acquire a socket
                sock = pool.Acquire();

                //Use the socket as a parameter to the delegate and return its result.
                if (sock != null)
                {
                    return use(sock);
                }
            }
            catch (Exception e)
            {
                Console.WriteLine("Error in Execute<T>: " + pool.Host);

                //Socket is probably broken
                if (sock != null)
                {
                    sock.Close();
                }
            }
            finally
            {
                if (sock != null)
                {
                    sock.Dispose();
                }
            }
            return defaultValue;
        }

        internal void Execute(SocketPool pool, UseSocket use)
        {
            PooledSocket sock = null;
            try
            {
                //Acquire a socket
                sock = pool.Acquire();

                //Use the socket as a parameter to the delegate and return its result.
                if (sock != null)
                {
                    use(sock);
                }
            }
            catch (Exception e)
            {
                Console.WriteLine("Error in Execute: " + pool.Host);

                //Socket is probably broken
                if (sock != null)
                {
                    sock.Close();
                }
            }
            finally
            {
                if (sock != null)
                {
                    sock.Dispose();
                }
            }
        }

        /// <summary>
        /// This method executes the given delegate on all servers.
        /// </summary>
        internal void ExecuteAll(UseSocket use)
        {
            foreach (SocketPool socketPool in hostList)
            {
                Execute(socketPool, use);
            }
        }
    }
    /// <summary>
    /// The SocketPool encapsulates the list of PooledSockets against one specific host, and contains methods for 
    /// acquiring or returning PooledSockets.
    /// </summary>
    [DebuggerDisplay("[ Host: {Host} ]")]
    internal class SocketPool
    {
        /// <summary>
        /// If the host stops responding, we mark it as dead for this amount of seconds, 
        /// and we double this for each consecutive failed retry. If the host comes alive
        /// again, we reset this to 1 again.
        /// </summary>
        private int deadEndPointSecondsUntilRetry = 1;
        private const int maxDeadEndPointSecondsUntilRetry = 60 10//10 minutes
        private ServerPool owner;
        private IPEndPoint endPoint;
        private Queue<PooledSocket> queue;

        //Debug variables and properties
        private int newsockets = 0;
        private int failednewsockets = 0;
        private int reusedsockets = 0;
        private int deadsocketsinpool = 0;
        private int deadsocketsonreturn = 0;
        private int dirtysocketsonreturn = 0;
        private int acquired = 0;
        public int NewSockets get return newsockets; } }
        public int FailedNewSockets get return failednewsockets; } }
        public int ReusedSockets get return reusedsockets; } }
        public int DeadSocketsInPool get return deadsocketsinpool; } }
        public int DeadSocketsOnReturn get return deadsocketsonreturn; } }
        public int DirtySocketsOnReturn get return dirtysocketsonreturn; } }
        public int Acquired get return acquired; } }
        public int Poolsize get return queue.Count; } }

        //Public variables and properties
        public readonly string Host;

        private bool isEndPointDead = false;
        public bool IsEndPointDead get return isEndPointDead; } }

        private DateTime deadEndPointRetryTime;
        public DateTime DeadEndPointRetryTime get return deadEndPointRetryTime; } }

        internal SocketPool(ServerPool owner, string host)
        {
            Host = host;
            this.owner = owner;
            endPoint = getEndPoint(host);
            queue = new Queue<PooledSocket>();
        }

        /// <summary>
        /// This method parses the given string into an IPEndPoint.
        /// If the string is malformed in some way, or if the host cannot be resolved, this method will throw an exception.
        /// </summary>
        private static IPEndPoint getEndPoint(string host)
        {
            //Parse port, default to 11211.
            int port = 11211;
            if (host.Contains(":"))
            {
                string[] split = host.Split(new char[] { ':' });
                if (!Int32.TryParse(split[1], out port))
                {
                    throw new ArgumentException("Unable to parse host: " + host);
                }
                host = split[0];
            }

            //Parse host string.
            IPAddress address;
            if (IPAddress.TryParse(host, out address))
            {
                //host string successfully resolved as an IP address.
            }
            else
            {
                //See if we can resolve it as a hostname
                try
                {
                    address = Dns.GetHostEntry(host).AddressList[0];
                }
                catch (Exception e)
                {
                    Console.WriteLine("Unable to resolve host: " + host);
                    return null;
                }
            }

            return new IPEndPoint(address, port);
        }

        /// <summary>
        /// Gets a socket from the pool.
        /// If there are no free sockets, a new one will be created. If something goes
        /// wrong while creating the new socket, this pool's endpoint will be marked as dead
        /// and all subsequent calls to this method will return null until the retry interval
        /// has passed.
        /// </summary>
        internal PooledSocket Acquire()
        {
            //Do we have free sockets in the pool?
            //if so - return the first working one.
            //if not - create a new one.
            Interlocked.Increment(ref acquired);
            lock (queue)
            {
                while (queue.Count > 0)
                {
                    PooledSocket socket = queue.Dequeue();
                    if (socket != null && socket.IsAlive)
                    {
                        Interlocked.Increment(ref reusedsockets);
                        return socket;
                    }
                    Interlocked.Increment(ref deadsocketsinpool);
                }
            }

            Interlocked.Increment(ref newsockets);
            //If we know the endpoint is dead, check if it is time for a retry, otherwise return null.
            if (isEndPointDead)
            {
                if (DateTime.Now > deadEndPointRetryTime)
                {
                    //Retry
                    isEndPointDead = false;
                }
                else
                {
                    //Still dead
                    return null;
                }
            }

            //Try to create a new socket. On failure, mark endpoint as dead and return null.
            try
            {
                PooledSocket socket = new PooledSocket(this, endPoint, owner.SendReceiveTimeout);
                //Reset retry timer on success.
                deadEndPointSecondsUntilRetry = 1;
                return socket;
            }
            catch (Exception e)
            {
                Interlocked.Increment(ref failednewsockets);
                Console.WriteLine("Error connecting to: " + endPoint.Address);
                //Mark endpoint as dead
                isEndPointDead = true;
                //Retry in 2 minutes
                deadEndPointRetryTime = DateTime.Now.AddSeconds(deadEndPointSecondsUntilRetry);
                if (deadEndPointSecondsUntilRetry < maxDeadEndPointSecondsUntilRetry)
                {
                    deadEndPointSecondsUntilRetry = deadEndPointSecondsUntilRetry * 2//Double retry interval until next time
                }
                return null;
            }
        }

        /// <summary>
        /// Returns a socket to the pool.
        /// If the socket is dead, it will be destroyed.
        /// If there are more than MaxPoolSize sockets in the pool, it will be destroyed.
        /// If there are less than MinPoolSize sockets in the pool, it will always be put back.
        /// If there are something inbetween those values, the age of the socket is checked. 
        /// If it is older than the SocketRrecycleAge, it is destroyed, otherwise it will be 
        /// put back in the pool.
        /// </summary>
        internal void Return(PooledSocket socket)
        {
            //If the socket is dead, destroy it.
            if (!socket.IsAlive)
            {
                Interlocked.Increment(ref deadsocketsonreturn);
                socket.Close();
            }
            else
            {
                //Clean up socket
                if (socket.Reset())
                {
                    Interlocked.Increment(ref dirtysocketsonreturn);
                }

                //Check pool size.
                if (queue.Count >= owner.MaxPoolSize)
                {
                    //If the pool is full, destroy the socket.
                    socket.Close();
                }
                else if (queue.Count > owner.MinPoolSize && DateTime.Now - socket.Created > owner.SocketRecycleAge)
                {
                    //If we have more than the minimum amount of sockets, but less than the max, and the socket is older than the recycle age, we destroy it.
                    socket.Close();
                }
                else
                {
                    //Put the socket back in the pool.
                    lock (queue)
                    {
                        queue.Enqueue(socket);
                    }
                }
            }
        }
    }
}

   
  
Related examples in the same category
1.new Socket
2.Socket Connect, Send
3.Socket Exception
4.Socket property
5.Creating Socket Connections
6.Thread and socketThread and socket
7.New Multi Send
8.Multi Send
9.Multi Receive
10.Server Pool
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