Polly

Telemetry

Starting with version 8, Polly provides telemetry for all built-in resilience strategies.

Usage

To enable telemetry in Polly, add the Polly.Extensions package to your project:

dotnet add package Polly.Extensions

Afterwards, you can use the ConfigureTelemetry(...) extension method on the ResiliencePipelineBuilder:

var telemetryOptions = new TelemetryOptions
{
    // Configure logging
    LoggerFactory = LoggerFactory.Create(builder => builder.AddConsole())
};

// Configure enrichers
telemetryOptions.MeteringEnrichers.Add(new MyMeteringEnricher());

// Configure telemetry listeners
telemetryOptions.TelemetryListeners.Add(new MyTelemetryListener());

var builder = new ResiliencePipelineBuilder()
    .AddTimeout(TimeSpan.FromSeconds(1))
    .ConfigureTelemetry(telemetryOptions) // This method enables telemetry in the builder
    .Build();

The MyTelemetryListener and MyMeteringEnricher is implemented as:

internal class MyTelemetryListener : TelemetryListener
{
    public override void Write<TResult, TArgs>(in TelemetryEventArguments<TResult, TArgs> args)
    {
        Console.WriteLine($"Telemetry event occurred: {args.Event.EventName}");
    }
}

internal class MyMeteringEnricher : MeteringEnricher
{
    public override void Enrich<TResult, TArgs>(in EnrichmentContext<TResult, TArgs> context)
    {
        context.Tags.Add(new("my-custom-tag", "custom-value"));
    }
}

Alternatively, you can use the AddResiliencePipeline(...) extension method which automatically enables telemetry for defined pipeline:

var serviceCollection = new ServiceCollection()
    .AddLogging(builder => builder.AddConsole())
    .AddResiliencePipeline("my-strategy", builder => builder.AddTimeout(TimeSpan.FromSeconds(1)))
    .Configure<TelemetryOptions>(options =>
    {
        // Configure enrichers
        options.MeteringEnrichers.Add(new MyMeteringEnricher());

        // Configure telemetry listeners
        options.TelemetryListeners.Add(new MyTelemetryListener());
    });

Metrics

The metrics are emitted under the Polly meter name. The subsequent sections provide insights into the metrics produced by Polly. Please note that any custom enriched dimensions are not depicted in the following tables.

Every telemetry event has the following dimensions:

• pipeline-name: Optional, comes from ResiliencePipelineBuilder.Name.
• pipeline-instance: Optional, comes from ResiliencePipelineBuilder.InstanceName.
• strategy-name: Optional, comes from RetryStrategyOptions.Name.

The sample below demonstrates how to assign these dimensions:

var builder = new ResiliencePipelineBuilder();
builder.Name = "my-name";
builder.Name = "my-instance-name";

builder.AddRetry(new RetryStrategyOptions
{
    // The default value is "Retry"
    Name = "my-retry-name"
});

These values are subsequently reflected in the metrics below:

resilience-events

• Type: Counter
• Description: Emitted upon the occurrence of a resilience event.

Dimensions:

Name	Description
event-name	The name of the emitted event.
event-severity	The severity of the event (Debug, Information, Warning, Error, Critical).
pipeline-name	The name of the pipeline corresponding to the resilience pipeline.
pipeline-instance	The instance name of the pipeline corresponding to the resilience pipeline.
strategy-name	The name of the strategy generating this event.
operation-key	The operation key associated with the call site.
exception-name	The full name of the exception assigned to the execution result (System.InvalidOperationException).

execution-attempt-duration

• Type: Histogram
• Unit: milliseconds
• Description: Tracks the duration of execution attempts, produced by Retry and Hedging resilience strategies.

Dimensions:

Name	Description
event-name	The name of the emitted event.
event-severity	The severity of the event (Debug, Information, Warning, Error, Critical).
pipeline-name	The name of the pipeline corresponding to the resilience pipeline.
pipeline-instance	The instance name of the pipeline corresponding to the resilience pipeline.
strategy-name	The name of the strategy generating this event.
operation-key	The operation key associated with the call site.
exception-name	The full name of the exception assigned to the execution result (System.InvalidOperationException).
attempt-number	The execution attempt number, starting at 0 (0, 1, 2, etc.).
attempt-handled	Indicates if the execution outcome was handled. A handled outcome indicates execution failure and the need for retry (true, false).

pipeline-execution-duration

• Type: Histogram
• Unit: milliseconds
• Description: Measures the duration of resilience pipelines.

Dimensions:

Name	Description
pipeline-name	The name of the pipeline corresponding to the resilience pipeline.
pipeline-instance	The instance name of the pipeline corresponding to the resilience pipeline.
operation-key	The operation key associated with the call site.
exception-name	The full name of the exception assigned to the execution result (System.InvalidOperationException).

Logs

Logs are registered under the Polly logger name. Here are some examples of the logs:

// This log is recorded whenever a resilience event occurs. EventId = 0
Resilience event occurred. EventName: '{EventName}', Source: '{PipelineName}/{PipelineInstance}/{StrategyName}', Operation Key: '{OperationKey}', Result: '{Result}'

// This log is recorded when a resilience pipeline begins executing. EventId = 1
Resilience pipeline executing. Source: '{PipelineName}/{PipelineInstance}', Operation Key: '{OperationKey}'

// This log is recorded when a resilience pipeline finishes execution. EventId = 2
Resilience pipeline executed. Source: '{PipelineName}/{PipelineInstance}', Operation Key: '{OperationKey}', Result: '{Result}', Execution Health: '{ExecutionHealth}', Execution Time: {ExecutionTime}ms

// This log is recorded upon the completion of every execution attempt. EventId = 3
Execution attempt. Source: '{PipelineName}/{PipelineInstance}/{StrategyName}', Operation Key: '{OperationKey}', Result: '{Result}', Handled: '{Handled}', Attempt: '{Attempt}', Execution Time: '{ExecutionTimeMs}'

Emitting telemetry events

Each resilience strategy can generate telemetry data through the ResilienceStrategyTelemetry API. Polly encapsulates event details as TelemetryEventArguments and emits them via TelemetryListener.

To leverage this telemetry data, users should assign a TelemetryListener instance to ResiliencePipelineBuilder.TelemetryListener and then consume the TelemetryEventArguments.

For common scenarios, it is expected that users would make use of Polly.Extensions. This extension enables telemetry configuration through the ResiliencePipelineBuilder.ConfigureTelemetry(...) method, which processes TelemetryEventArguments to generate logs and metrics.

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