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ServerMonitor.cs
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/
ServerMonitor.cs
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/* Copyright 2016-present MongoDB Inc.
*
* Licensed 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.
*/
using System;
using System.Diagnostics;
using System.Net;
using System.Threading;
using System.Threading.Tasks;
using MongoDB.Bson;
using MongoDB.Bson.Serialization.Serializers;
using MongoDB.Driver.Core.Connections;
using MongoDB.Driver.Core.Events;
using MongoDB.Driver.Core.Misc;
using MongoDB.Driver.Core.WireProtocol;
namespace MongoDB.Driver.Core.Servers
{
internal sealed class ServerMonitor : IServerMonitor
{
private static readonly TimeSpan __minHeartbeatInterval = TimeSpan.FromMilliseconds(500);
private readonly ExponentiallyWeightedMovingAverage _averageRoundTripTimeCalculator = new ExponentiallyWeightedMovingAverage(0.2);
private readonly ServerDescription _baseDescription;
private readonly CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
private volatile IConnection _connection;
private readonly IConnectionFactory _connectionFactory;
private ServerDescription _currentDescription;
private readonly EndPoint _endPoint;
private HeartbeatDelay _heartbeatDelay;
private readonly TimeSpan _heartbeatInterval;
private readonly ServerId _serverId;
private readonly InterlockedInt32 _state;
private readonly TimeSpan _timeout;
private readonly Action<ServerHeartbeatStartedEvent> _heartbeatStartedEventHandler;
private readonly Action<ServerHeartbeatSucceededEvent> _heartbeatSucceededEventHandler;
private readonly Action<ServerHeartbeatFailedEvent> _heartbeatFailedEventHandler;
public event EventHandler<ServerDescriptionChangedEventArgs> DescriptionChanged;
public ServerMonitor(ServerId serverId, EndPoint endPoint, IConnectionFactory connectionFactory, TimeSpan heartbeatInterval, TimeSpan timeout, IEventSubscriber eventSubscriber)
{
_serverId = Ensure.IsNotNull(serverId, nameof(serverId));
_endPoint = Ensure.IsNotNull(endPoint, nameof(endPoint));
_connectionFactory = Ensure.IsNotNull(connectionFactory, nameof(connectionFactory));
Ensure.IsNotNull(eventSubscriber, nameof(eventSubscriber));
_baseDescription = _currentDescription = new ServerDescription(_serverId, endPoint, heartbeatInterval: heartbeatInterval);
_heartbeatInterval = heartbeatInterval;
_timeout = timeout;
_state = new InterlockedInt32(State.Initial);
eventSubscriber.TryGetEventHandler(out _heartbeatStartedEventHandler);
eventSubscriber.TryGetEventHandler(out _heartbeatSucceededEventHandler);
eventSubscriber.TryGetEventHandler(out _heartbeatFailedEventHandler);
}
public ServerDescription Description => Interlocked.CompareExchange(ref _currentDescription, null, null);
public void Dispose()
{
if (_state.TryChange(State.Disposed))
{
_cancellationTokenSource.Cancel();
_cancellationTokenSource.Dispose();
if (_connection != null)
{
_connection.Dispose();
}
}
}
public void Initialize()
{
if (_state.TryChange(State.Initial, State.Open))
{
MonitorServerAsync().ConfigureAwait(false);
}
}
public void Invalidate()
{
OnDescriptionChanged(_baseDescription);
RequestHeartbeat();
}
public void RequestHeartbeat()
{
ThrowIfNotOpen();
var heartbeatDelay = Interlocked.CompareExchange(ref _heartbeatDelay, null, null);
if (heartbeatDelay != null)
{
heartbeatDelay.RequestHeartbeat();
}
}
private async Task MonitorServerAsync()
{
var metronome = new Metronome(_heartbeatInterval);
var heartbeatCancellationToken = _cancellationTokenSource.Token;
while (!heartbeatCancellationToken.IsCancellationRequested)
{
try
{
await HeartbeatAsync(heartbeatCancellationToken).ConfigureAwait(false);
var newHeartbeatDelay = new HeartbeatDelay(metronome.GetNextTickDelay(), __minHeartbeatInterval);
var oldHeartbeatDelay = Interlocked.Exchange(ref _heartbeatDelay, newHeartbeatDelay);
if (oldHeartbeatDelay != null)
{
oldHeartbeatDelay.Dispose();
}
await newHeartbeatDelay.Task.ConfigureAwait(false);
}
catch
{
// ignore these exceptions
}
}
}
private async Task<bool> HeartbeatAsync(CancellationToken cancellationToken)
{
const int maxRetryCount = 2;
HeartbeatInfo heartbeatInfo = null;
Exception heartbeatException = null;
for (var attempt = 1; attempt <= maxRetryCount; attempt++)
{
var connection = _connection;
try
{
if (connection == null)
{
connection = _connectionFactory.CreateConnection(_serverId, _endPoint);
// if we are cancelling, it's because the server has
// been shut down and we really don't need to wait.
await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
}
heartbeatInfo = await GetHeartbeatInfoAsync(connection, cancellationToken).ConfigureAwait(false);
heartbeatException = null;
_connection = connection;
break;
}
catch (Exception ex)
{
heartbeatException = ex;
_connection = null;
if (connection != null)
{
connection.Dispose();
}
}
}
ServerDescription newDescription;
if (heartbeatInfo != null)
{
var averageRoundTripTime = _averageRoundTripTimeCalculator.AddSample(heartbeatInfo.RoundTripTime);
var averageRoundTripTimeRounded = TimeSpan.FromMilliseconds(Math.Round(averageRoundTripTime.TotalMilliseconds));
var isMasterResult = heartbeatInfo.IsMasterResult;
var buildInfoResult = heartbeatInfo.BuildInfoResult;
newDescription = _baseDescription.With(
averageRoundTripTime: averageRoundTripTimeRounded,
canonicalEndPoint: isMasterResult.Me,
electionId: isMasterResult.ElectionId,
lastWriteTimestamp: isMasterResult.LastWriteTimestamp,
logicalSessionTimeout: isMasterResult.LogicalSessionTimeout,
maxBatchCount: isMasterResult.MaxBatchCount,
maxDocumentSize: isMasterResult.MaxDocumentSize,
maxMessageSize: isMasterResult.MaxMessageSize,
replicaSetConfig: isMasterResult.GetReplicaSetConfig(),
state: ServerState.Connected,
tags: isMasterResult.Tags,
type: isMasterResult.ServerType,
version: buildInfoResult.ServerVersion,
wireVersionRange: new Range<int>(isMasterResult.MinWireVersion, isMasterResult.MaxWireVersion));
}
else
{
newDescription = _baseDescription;
}
if (heartbeatException != null)
{
newDescription = newDescription.With(heartbeatException: heartbeatException);
}
OnDescriptionChanged(newDescription);
return true;
}
private async Task<HeartbeatInfo> GetHeartbeatInfoAsync(IConnection connection, CancellationToken cancellationToken)
{
cancellationToken.ThrowIfCancellationRequested();
if (_heartbeatStartedEventHandler != null)
{
_heartbeatStartedEventHandler(new ServerHeartbeatStartedEvent(connection.ConnectionId));
}
try
{
var isMasterCommand = new CommandWireProtocol<BsonDocument>(
DatabaseNamespace.Admin,
new BsonDocument("isMaster", 1),
true,
BsonDocumentSerializer.Instance,
null);
var stopwatch = Stopwatch.StartNew();
var isMasterResultDocument = await isMasterCommand.ExecuteAsync(connection, cancellationToken).ConfigureAwait(false);
stopwatch.Stop();
var isMasterResult = new IsMasterResult(isMasterResultDocument);
var buildInfoCommand = new CommandWireProtocol<BsonDocument>(
DatabaseNamespace.Admin,
new BsonDocument("buildInfo", 1),
true,
BsonDocumentSerializer.Instance,
null);
var buildInfoResultRocument = await buildInfoCommand.ExecuteAsync(connection, cancellationToken).ConfigureAwait(false);
var buildInfoResult = new BuildInfoResult(buildInfoResultRocument);
if (_heartbeatSucceededEventHandler != null)
{
_heartbeatSucceededEventHandler(new ServerHeartbeatSucceededEvent(connection.ConnectionId, stopwatch.Elapsed));
}
return new HeartbeatInfo
{
RoundTripTime = stopwatch.Elapsed,
IsMasterResult = isMasterResult,
BuildInfoResult = buildInfoResult
};
}
catch (Exception ex)
{
if (_heartbeatFailedEventHandler != null)
{
_heartbeatFailedEventHandler(new ServerHeartbeatFailedEvent(connection.ConnectionId, ex));
}
throw;
}
}
private void OnDescriptionChanged(ServerDescription newDescription)
{
var oldDescription = Interlocked.CompareExchange(ref _currentDescription, null, null);
if (oldDescription.Equals(newDescription))
{
return;
}
Interlocked.Exchange(ref _currentDescription, newDescription);
var handler = DescriptionChanged;
if (handler != null)
{
var args = new ServerDescriptionChangedEventArgs(oldDescription, newDescription);
try { handler(this, args); }
catch { } // ignore exceptions
}
}
private void ThrowIfDisposed()
{
if (_state.Value == State.Disposed)
{
throw new ObjectDisposedException(GetType().Name);
}
}
private void ThrowIfNotOpen()
{
if (_state.Value != State.Open)
{
ThrowIfDisposed();
throw new InvalidOperationException("Server monitor must be initialized.");
}
}
// nested types
private static class State
{
public const int Initial = 0;
public const int Open = 1;
public const int Disposed = 2;
}
private class HeartbeatInfo
{
public TimeSpan RoundTripTime;
public IsMasterResult IsMasterResult;
public BuildInfoResult BuildInfoResult;
}
}
}