Can I use Polly's telemetry features to log errors in MvvmCross

Using Polly's Telemetry Features with MvvmCross

Polly is a .NET library that provides resilience and fault-tolerance capabilities, including retries, circuit breakers, and timeouts. It also offers telemetry features to monitor and log events related to these strategies. MvvmCross is a framework for cross-platform app development that uses Microsoft.Extensions.Logging for logging purposes starting from version 8.

Polly Telemetry Overview

Polly's telemetry features are designed to provide insights into the execution of resilience strategies. These features can be enabled by installing the `Polly.Extensions` NuGet package and configuring telemetry using the `ConfigureTelemetry` method. Telemetry events include `ExecutionAttempt`, which reports each attempt made by a strategy like retry or hedging, and `OnRetry`, which logs when a retry is about to occur[4][7].

Integrating Polly Telemetry with MvvmCross Logging

To integrate Polly's telemetry with MvvmCross logging, you would typically use Microsoft.Extensions.Logging, which MvvmCross supports. Here’s how you can approach this:

1. Install Required Packages: Ensure you have Polly and its extensions installed in your project. You also need a logging provider like Serilog or NLog for more advanced logging capabilities.

2. Configure Polly Telemetry: Use the `ConfigureTelemetry` method to set up Polly to log telemetry events. You can pass an `ILoggerFactory` instance to this method to integrate with your logging infrastructure[4].

3. MvvmCross Logging Setup: In MvvmCross, you can inject an `ILogger` or `ILoggerFactory` into your view models or services. This allows you to log messages using the Microsoft.Extensions.Logging API[2].

4. Logging Polly Telemetry Events: Since Polly's telemetry is logged using the provided logger factory, you can configure your logging framework to handle these events. For example, you might want to filter out certain log levels or messages to avoid clutter.

Example Configuration

Here’s a simplified example of how you might configure Polly to use telemetry with Serilog logging in an MvvmCross application:

csharp
using Microsoft.Extensions.Logging;
using Polly;
using Serilog;

public class MyViewModel : MvxViewModel
{
    private readonly ILogger _logger;

    public MyViewModel(ILogger logger)
    {
        _logger = logger;
    }

    public void ConfigurePolly()
    {
        var loggerFactory = LoggerFactory.Create(builder =>
        {
            builder.AddSerilog(new LoggerConfiguration()
                .MinimumLevel.Debug()
                .WriteTo.Console()
                .CreateLogger());
        });

        var pipelineBuilder = new ResiliencePipelineBuilder()
            .AddRetry(new RetryStrategyOptions
            {
                MaxRetryAttempts = 3,
                Delay = TimeSpan.FromSeconds(2),
                BackoffType = DelayBackoffType.Exponential,
                ShouldHandle = new PredicateBuilder().Handle(),
                OnRetry = retryArguments =>
                {
                    _logger.LogWarning($"Retry attempt {retryArguments.AttemptNumber} failed with exception {retryArguments.Outcome.Exception.Message}.");
                    return ValueTask.CompletedTask;
                }
            })
            .ConfigureTelemetry(new TelemetryOptions { LoggerFactory = loggerFactory });

        // Use the pipeline builder to execute resilient operations
    }
}

Challenges and Considerations

- Filtering Telemetry Logs: Polly's telemetry logs are emitted regardless of whether retries occur. You might need to filter these logs at the logging framework level to avoid clutter[1].
- Log Level Configuration: Ensure that your logging configuration allows the desired level of detail from Polly's telemetry. You might need to adjust log levels or implement custom filtering to manage log output effectively.

By integrating Polly's telemetry with MvvmCross logging, you can enhance the visibility and management of resilience strategies in your cross-platform applications. However, be mindful of the potential need to filter or configure log levels to avoid unnecessary log clutter.