How can I integrate Polly with Serilog for error logging in MvvmCross

Step 1: Install Required NuGet Packages

First, ensure you have the necessary NuGet packages installed in your project. You need `Polly`, `Serilog`, and `Serilog.Extensions.Logging` for integration with Microsoft.Extensions.Logging, which MvvmCross uses starting from version 8.

bash
dotnet add package Polly
dotnet add package Serilog
dotnet add package Serilog.Extensions.Logging

Step 2: Configure Serilog

In your MvvmCross setup, you need to configure Serilog to work with Microsoft.Extensions.Logging. This involves creating a logger configuration and adding it to the DI container.

csharp
protected override ILoggerProvider CreateLogProvider()
{
    Log.Logger = new LoggerConfiguration()
        .MinimumLevel.Debug()
        // Add more sinks here, e.g., to log to a file
        .WriteTo.Console()
        .CreateLogger();

    return new SerilogLoggerProvider();
}

protected override ILoggerFactory CreateLogFactory()
{
    return new SerilogLoggerFactory();
}

Step 3: Use Polly with Serilog Logging

To integrate Polly with Serilog for logging, you can use the Polly context to pass an instance of `ILogger` to the policy execution. Here's how you can do it:

1. Create a Polly Policy: Define a Polly policy that handles exceptions and retries operations.

2. Pass ILogger to Polly Context: Use the Polly context to pass an instance of `ILogger` to the policy execution.

3. Log Errors: Use the `onRetryAsync` and `onBreakAsync` callbacks to log errors using Serilog.

Here's an example of how you might implement this:

csharp
using Polly;
using Serilog;

public class MyViewModel : MvxViewModel
{
    private readonly ILogger _logger;
    private readonly AsyncRetryPolicy _retryPolicy;

    public MyViewModel(ILogger logger)
    {
        _logger = logger;

        _retryPolicy = Policy.Handle()
            .WaitAndRetryAsync(
                retryCount: 3,
                retryAttempt => TimeSpan.FromMilliseconds(retryAttempt * 500),
                (exception, ts) => LogRetry(_logger, exception, ts),
                (exception, ts) => LogBreak(_logger, exception, ts)
            );
    }

    private void LogRetry(ILogger logger, Exception exception, TimeSpan ts)
    {
        logger.LogError(exception, $"Retry after {ts.TotalMilliseconds}ms");
    }

    private void LogBreak(ILogger logger, Exception exception, TimeSpan ts)
    {
        logger.LogError(exception, "Final attempt failed");
    }

    public async Task DoSomethingAsync()
    {
        await _retryPolicy.ExecuteAsync(async () =>
        {
            // Code that might throw an exception
        });
    }
}

Step 4: Execute Polly Policy with Logging

When executing the Polly policy, ensure that you are using the configured logger to log any errors or retries. The example above demonstrates how to log retries and final failures using Serilog.

Conclusion

By following these steps, you can effectively integrate Polly with Serilog for robust error logging in MvvmCross applications. This setup allows you to handle exceptions gracefully while logging important events for debugging and monitoring purposes.