Holds the ping times and a rolling calculated average. This class is thread-safe.
        // constructors
        /// <summary>
        /// Initializes a new instance of the <see cref="MongoServerInstance"/> class.
        /// </summary>
        /// <param name="settings">The settings.</param>
        /// <param name="address">The address.</param>
        internal MongoServerInstance(MongoServerSettings settings, MongoServerAddress address)
        {
            _settings = settings;
            _address = address;
            _sequentialId = Interlocked.Increment(ref __nextSequentialId);
            _state = MongoServerState.Disconnected;
            _serverInfo = new ServerInformation
            {
                MaxDocumentSize = MongoDefaults.MaxDocumentSize,
                MaxMessageLength = MongoDefaults.MaxMessageLength,
                InstanceType = MongoServerInstanceType.Unknown
            };
            _connectionPool = new MongoConnectionPool(this);
            _pingTimeAggregator = new PingTimeAggregator(5);
            _permanentlyDisconnected = false;
            // Console.WriteLine("MongoServerInstance[{0}]: {1}", sequentialId, address);

            _stateVerificationAcquireConnectionOptions = new MongoConnectionPool.AcquireConnectionOptions
            {
                OkToAvoidWaitingByCreatingNewConnection = false,
                OkToExceedMaxConnectionPoolSize = true,
                OkToExceedWaitQueueSize = true,
                WaitQueueTimeout = TimeSpan.FromSeconds(2)
            };
        }
 // constructors
 /// <summary>
 /// Initializes a new instance of the <see cref="MongoServerInstance"/> class.
 /// </summary>
 /// <param name="settings">The settings.</param>
 /// <param name="address">The address.</param>
 internal MongoServerInstance(MongoServerSettings settings, MongoServerAddress address)
 {
     _settings = settings;
     _address = address;
     _sequentialId = Interlocked.Increment(ref __nextSequentialId);
     _state = MongoServerState.Disconnected;
     _serverInfo = new ServerInformation
     {
         MaxDocumentSize = MongoDefaults.MaxDocumentSize,
         MaxMessageLength = MongoDefaults.MaxMessageLength,
         InstanceType = MongoServerInstanceType.Unknown
     };
     _connectionPool = new MongoConnectionPool(this);
     _pingTimeAggregator = new PingTimeAggregator(5);
     _permanentlyDisconnected = false;
     // Console.WriteLine("MongoServerInstance[{0}]: {1}", sequentialId, address);
 }
 // constructors
 /// <summary>
 /// Initializes a new instance of the <see cref="MongoServerInstance"/> class.
 /// </summary>
 /// <param name="server">The server.</param>
 /// <param name="address">The address.</param>
 internal MongoServerInstance(MongoServer server, MongoServerAddress address)
 {
     _server = server;
     _address = address;
     _sequentialId = Interlocked.Increment(ref __nextSequentialId);
     _maxDocumentSize = MongoDefaults.MaxDocumentSize;
     _maxMessageLength = MongoDefaults.MaxMessageLength;
     _state = MongoServerState.Disconnected;
     _instanceType = MongoServerInstanceType.Unknown;
     _connectionPool = new MongoConnectionPool(this);
     _pingTimeAggregator = new PingTimeAggregator(5);
     _stateVerificationTimer = new Timer(o => StateVerificationTimerCallback(), null, TimeSpan.Zero, TimeSpan.FromSeconds(10));
     // Console.WriteLine("MongoServerInstance[{0}]: {1}", sequentialId, address);
 }