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LatencyLimitingServerSelector.cs
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LatencyLimitingServerSelector.cs
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/* Copyright 2013-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.Collections.Generic;
using System.Linq;
using System.Threading;
using MongoDB.Driver.Core.Misc;
using MongoDB.Driver.Core.Servers;
namespace MongoDB.Driver.Core.Clusters.ServerSelectors
{
/// <summary>
/// Represents a selector that selects servers within an acceptable latency range.
/// </summary>
public class LatencyLimitingServerSelector : IServerSelector
{
// fields
private readonly TimeSpan _allowedLatencyRange;
// constructors
/// <summary>
/// Initializes a new instance of the <see cref="LatencyLimitingServerSelector"/> class.
/// </summary>
public LatencyLimitingServerSelector()
: this(TimeSpan.FromMilliseconds(15))
{
}
/// <summary>
/// Initializes a new instance of the <see cref="LatencyLimitingServerSelector"/> class.
/// </summary>
/// <param name="allowedLatencyRange">The allowed latency range.</param>
public LatencyLimitingServerSelector(TimeSpan allowedLatencyRange)
{
_allowedLatencyRange = Ensure.IsInfiniteOrGreaterThanOrEqualToZero(allowedLatencyRange, nameof(allowedLatencyRange));
}
// methods
/// <inheritdoc/>
public IEnumerable<ServerDescription> SelectServers(ClusterDescription cluster, IEnumerable<ServerDescription> servers)
{
if (_allowedLatencyRange == Timeout.InfiniteTimeSpan)
{
return servers;
}
var list = servers.ToList();
switch (list.Count)
{
case 0:
case 1:
return list;
default:
var minAverageRoundTripTime = list.Min(s => s.AverageRoundTripTime);
var maxAverageRoundTripTime = minAverageRoundTripTime.Add(_allowedLatencyRange);
return list.Where(s => s.AverageRoundTripTime <= maxAverageRoundTripTime);
}
}
/// <inheritdoc/>
public override string ToString()
{
return string.Format("LatencyLimitingServerSelector{{ AllowedLatencyRange = {0} }}", _allowedLatencyRange);
}
}
}