Worker Dependency Injection Demo

.NET Core gives us really cool out of the box dependency injection, but its is really only wired up for you with ASP.NET. This repo will show you two ways to wire it up for service workers.

What kinds of services will this approach work for

• Console Apps
• Custom Services
• Linux Services
• AWS Lambdas
• Azure WebJobs
• Azure Functions
• Windows Services
• Service Fabric Actors

Two Types

There are really only two types of workers in the list ablove

Run Once

• Console apps
• AWS Lambdas
• Azure WebJobs
• Azure Functions

Hosted Service

• Custom Services
• Linux Services
• Windows Services
• Service Fabric Actors

What's in Common between the two?

The two share a lot of the same components

• Configuration Builder
• Service Collection / Service Provider
• Logger / Logging Builder

Configuration Builder

1. Can be pull in many sources

• Environment Variables
• Command Line
• JSON
• XML
• Azure Key Vault
• Azure Application Configuration
• AWS Parameter Store

2. Can be built more than once allowing to use settings in the first build to create the second

    var configurationBuilder = new ConfigurationBuilder()
      .AddEnvironmentVariables("DOTNETCORE_")
    
    //get the environment settings
    var environment = configurationBuilder
      .Build()
      .GetValue<string>("Environment");
    
    //add config files per environment
    configurationBuilder
      .AddJsonFile($"consolesettings.{environment}.json", false, false);
    
    //build the configuration for the container
    var configuration = configurationBuilder
      .Build();
   

Service Collection / Service Provider

Allows registering:

• interfaces with implementation
• implementations
• factory methods

Allows for the lifetimes:

• Transient - new every time
• Scoped - new once per scope
• Singleton - only once

Logging Builder

Allows multiple providers:

• Console
• Debugger
• Event Log
• File based
• Azure Monitor
• AWS Cloudwatch

Allows for levels:

• Trace
• Debug
• Information
• Warning
• Error
• Critical

Can be configured

• With Configuration Builder
• In Code

Also allows log level per namespace, allowing you to override log levels in a tree structure. In the Example Below you'd get all queries and commands from Entity Framework but only Errors from the rest of Microsoft Components

    "Microsoft": "Error",
    "Microsoft.EntityFrameworkCore.Database": "Information"

But Hosted Services have an extra layer

For hosted services there is a Host Builder it breaks up

• Host Configuration
• App Configuration
• Logging
• Services

  • Adds a special type of registration for IHostedService

      await new HostBuilder().ConfigureHostConfiguration(configuration =>
      {
          //Get your enviornment variables with command line overrides
          configuration
              .AddEnvironmentVariables("DOTNETCORE_")
              .AddCommandLine(args);
      })
      .ConfigureAppConfiguration((hostContext, configuration) =>
      {
          //get your config files, per environment
          configuration
              .AddJsonFile("appsettings.json", false, true)
              .AddJsonFile($"appsettings.{hostContext.HostingEnvironment.EnvironmentName}.json",
                  false, true);
          
          //optionally add in azure app config by setting a connection string AppConfig
          var appConfig = configuration.Build().GetConnectionString("AppConfig");
          if(!string.IsNullOrWhiteSpace(appConfig))
              configuration.AddAzureAppConfiguration(appConfig);
    
      })
      .ConfigureLogging((hostContext, logging) =>
      {
          //setup logging including azure monitor
          var logConfig = hostContext.Configuration.GetSection("Logging");
    
          logging
              .AddConfiguration(logConfig)
              .AddDebug()
              .AddConsole()
              .AddEventSourceLogger()
              .AddApplicationInsights();
      })
      .ConfigureServices((hostContext, services) =>
      {
          //register telemetry, your dependencies and your HostedService
          services
              .AddApplicationInsightsTelemetryWorkerService()
              .AddSingleton<IMyDependency1, MyDependency1>()
              .AddHostedService<MyWoker>();
      })
      .RunConsoleAsync();
    

Available out of the box IHostedServices

• ASP.NETcore - Microsoft.AspNetCore
• WebJobs - Microsoft.Azure.WebJobs.Core
• Windows Services - Microsoft.Extensions.Hosting.WindowsServices

Extras

• InMemory EF Core Database - not just for testing
• Azure Application Insights/Monitor for tracking stats

Demos

• Console Application for a TODO List using InMemory EF Core
  • Unit Tests
    • Wrapping the Console
  • Running in a debugger
  • Running via command line
• Custom Worker Service using AppInsights to track random number metrics
  • Unit Tests
    • Wrapping Microsoft's TelemetryClient
  • Running in a debugger
  • Running via command line