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ParentBasedSampler.cs
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ParentBasedSampler.cs
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// <copyright file="ParentBasedSampler.cs" company="OpenTelemetry Authors">
// Copyright The OpenTelemetry Authors
//
// 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.
// </copyright>
using System;
using System.Diagnostics;
namespace OpenTelemetry.Trace
{
/// <summary>
/// Sampler implementation which by default will take a sample if parent Activity is sampled.
/// Otherwise, samples root traces according to the specified root sampler.
/// </summary>
/// <remarks>
/// The default behavior can be customized by providing additional samplers to be invoked for different
/// combinations of local/remote parent and its sampling decision.
/// See <see cref="ParentBasedSampler(Sampler, Sampler, Sampler, Sampler, Sampler)"/>.
/// </remarks>
public sealed class ParentBasedSampler : Sampler
{
private readonly Sampler rootSampler;
private readonly Sampler remoteParentSampled;
private readonly Sampler remoteParentNotSampled;
private readonly Sampler localParentSampled;
private readonly Sampler localParentNotSampled;
/// <summary>
/// Initializes a new instance of the <see cref="ParentBasedSampler"/> class.
/// </summary>
/// <param name="rootSampler">The <see cref="Sampler"/> to be called for root span/activity.</param>
public ParentBasedSampler(Sampler rootSampler)
{
this.rootSampler = rootSampler ?? throw new ArgumentNullException(nameof(rootSampler));
this.Description = $"ParentBased{{{rootSampler.Description}}}";
this.remoteParentSampled = new AlwaysOnSampler();
this.remoteParentNotSampled = new AlwaysOffSampler();
this.localParentSampled = new AlwaysOnSampler();
this.localParentNotSampled = new AlwaysOffSampler();
}
/// <summary>
/// Initializes a new instance of the <see cref="ParentBasedSampler"/> class with ability to delegate
/// sampling decision to one of the inner samplers provided.
/// </summary>
/// <param name="rootSampler">The <see cref="Sampler"/> to be called for root span/activity.</param>
/// <param name="remoteParentSampled">
/// A <see cref="Sampler"/> to delegate sampling decision to in case of
/// remote parent (<see cref="ActivityContext.IsRemote"/> == true) with <see cref="ActivityTraceFlags.Recorded"/> flag == true.
/// Default: <see cref="AlwaysOnSampler"/>.
/// </param>
/// <param name="remoteParentNotSampled">
/// A <see cref="Sampler"/> to delegate sampling decision to in case of
/// remote parent (<see cref="ActivityContext.IsRemote"/> == true) with <see cref="ActivityTraceFlags.Recorded"/> flag == false.
/// Default: <see cref="AlwaysOffSampler"/>.
/// </param>
/// <param name="localParentSampled">
/// A <see cref="Sampler"/> to delegate sampling decision to in case of
/// local parent (<see cref="ActivityContext.IsRemote"/> == false) with <see cref="ActivityTraceFlags.Recorded"/> flag == true.
/// Default: <see cref="AlwaysOnSampler"/>.
/// </param>
/// <param name="localParentNotSampled">
/// A <see cref="Sampler"/> to delegate sampling decision to in case of
/// local parent (<see cref="ActivityContext.IsRemote"/> == false) with <see cref="ActivityTraceFlags.Recorded"/> flag == false.
/// Default: <see cref="AlwaysOffSampler"/>.
/// </param>
public ParentBasedSampler(
Sampler rootSampler,
Sampler remoteParentSampled = null,
Sampler remoteParentNotSampled = null,
Sampler localParentSampled = null,
Sampler localParentNotSampled = null)
: this(rootSampler)
{
this.remoteParentSampled = remoteParentSampled ?? new AlwaysOnSampler();
this.remoteParentNotSampled = remoteParentNotSampled ?? new AlwaysOffSampler();
this.localParentSampled = localParentSampled ?? new AlwaysOnSampler();
this.localParentNotSampled = localParentNotSampled ?? new AlwaysOffSampler();
}
/// <inheritdoc />
public override SamplingResult ShouldSample(in SamplingParameters samplingParameters)
{
var parentContext = samplingParameters.ParentContext;
if (parentContext.TraceId == default)
{
// If no parent, use the rootSampler to determine sampling.
return this.rootSampler.ShouldSample(samplingParameters);
}
// Is parent sampled?
if ((parentContext.TraceFlags & ActivityTraceFlags.Recorded) != 0)
{
if (parentContext.IsRemote)
{
return this.remoteParentSampled.ShouldSample(samplingParameters);
}
else
{
return this.localParentSampled.ShouldSample(samplingParameters);
}
}
// If parent is not sampled => delegate to the "not sampled" inner samplers.
if (parentContext.IsRemote)
{
return this.remoteParentNotSampled.ShouldSample(samplingParameters);
}
else
{
return this.localParentNotSampled.ShouldSample(samplingParameters);
}
}
}
}