Using Arcus & Serilog in .NET Core and/or Azure Functions

When using Arcus Observability & Serilog it is mandatory that your application is configured correctly to ensure everything works smoothly and all features are working fine.

We encourage you to follow the standard Serilog instructions on setting your application up.

Some aspects we would like to highlight are:

• Make sure to call UseSerilog when creating a IHostBuilder
• Remove default for logging including its configuration in appsettings.json (if applicable)

If you cannot use UseSerilog, you can still configure it by using AddSerilog as a logging provider; but we recommend removing all other providers with loggingBuilder.ClearProviders() so that they don't interfer.

Setting up Serilog with Azure Functions

Using Serilog with Azure Functions requires some guidance and we've made it a bit easier to use.

Before we get started, install our NuGet package for Azure Functions:

PM > Install-Package -Name Arcus.Observability.Telemetry.AzureFunctions

Once that is done, you can configure Serilog during startup as following:

using Microsoft.Extensions.Logging;

[assembly: FunctionsStartup(typeof(Startup))]
namespace Arcus.Samples.AzureFunction
{
    public class Startup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            var config = builder.GetContext().Configuration;

            var instrumentationKey = config.GetValue<string>("APPINSIGHTS_INSTRUMENTATIONKEY");

            var logger = new LoggerConfiguration()
                .MinimumLevel.Debug()
                .MinimumLevel.Override("Microsoft", LogEventLevel.Information)
                .Enrich.FromLogContext()
                .Enrich.WithComponentName("Docker Hub Metrics Scraper")
                .Enrich.WithVersion()
                .WriteTo.Console()
                .WriteTo.AzureApplicationInsights(instrumentationKey)
                .CreateLogger();

            builder.Services.AddLogging(loggingBuilder =>
            {
                loggingBuilder.ClearProvidersExceptFunctionProviders();
                loggingBuilder.AddSerilog(logger);
            });
        }
    }
}

💡 Note that we are using ClearProvidersExceptFunctionProviders instead of ClearProviders given Azure Functions requires some logging providers to be available.

Here is an example of how you can use ILogger to write multi-dimensional metrics with Arcus. If Serilog would not be setup correctly (see above), it would only report the metric without the dimensions.

using Microsoft.Azure.Databricks.Client;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;

public class DockerHubMetricScraperFunction
{
    private readonly DockerHubClient _dockerHubClient;
    private readonly IConfiguration _configuration;
    private readonly ILogger<DockerHubMetricScraperFunction> _logger;

    public DockerHubMetricScraperFunction(DockerHubClient dockerHubClient, IConfiguration configuration, ILogger<DockerHubMetricScraperFunction> logger)
    {
        Guard.NotNull(dockerHubClient, nameof(dockerHubClient));
        Guard.NotNull(configuration, nameof(configuration));
        Guard.NotNull(logger, nameof(logger));

        _dockerHubClient = dockerHubClient;
        _configuration = configuration;
        _logger = logger;
    }

    [FunctionName("docker-hub-metric-scraper")]
    public async Task Run([TimerTrigger("0 */15 * * * *")] TimerInfo timer)
    {
        _logger.LogInformation($"Starting to scrape Docker Hub metrics at {DateTime.UtcNow}");

        var repoName = _configuration["DOCKER_HUB_REPO_NAME"];
        var imageName = _configuration["DOCKER_HUB_IMAGE_NAME"];

        var pullCount = await _dockerHubClient.GetImageMetricsAsync(repoName, imageName);

        var contextualInformation = new Dictionary<string, object>
        {
            {"Repo Name", repoName},
            {"Image Name", imageName},
            {"Image ID", $"{repoName}/{imageName}"}
        };

        _logger.LogMetric("Image Pulls", pullCount, contextualInformation);
    }
}