Plugins.md

How to implement an observer using FO's extensibility model

Note that starting in version 2.2.0, ClusterObserver supports the FO plugin model. So, you can build cluster-level monitoring plugins should you so desire.

1. Create a .NET 8 Library project.

2. Install the latest Microsoft.ServiceFabricApps.FabricObserver.Extensibility nupkg from https://www.nuget.org/profiles/ServiceFabricApps into your plugin project.

3. Write a custom observer!

   E.g., create a new class file, MyObserver.cs.

   This is the required signature for your plugin's constructor:

    // FO will provide (and manage) both the FabricClient instance and StatelessServiceContext instance during startup.
    public MyObserver(FabricClient fabricClient, StatelessServiceContext context) : base(fabricClient, context)
    {
    }

You must implement ObserverBase's two abstract functions:

    public override Task ObserveAsync()
    {
    }

    public override Task ReportAsync()
    {
    }

4. Create a [ObserverTypeName]Startup.cs file with this format (e.g., MyObserver is the name of your observer class.):

    using System.Fabric;
    using FabricObserver;
    using FabricObserver.Observers;
    using Microsoft.Extensions.DependencyInjection;

    [assembly: FabricObserverStartup(typeof(MyObserverStartup))]
    namespace FabricObserver.Observers
    {
        public class MyObserverStartup : IFabricObserverStartup
        {
            public void ConfigureServices(IServiceCollection services, FabricClient fabricClient, StatelessServiceContext context)
            {
                services.AddScoped(typeof(ObserverBase), s => new MyObserver(fabricClient, context));
            }
        }
    }

5. Build your observer project, drop the output dll and ALL of its dependencies, both managed and native (this is very important), into the Data/Plugins folder in FabricObserver/PackageRoot. You can place your plugin dll and all of its dependencies in its own (same) folder under the Plugins directory (useful if you have multiple plugins). Again, ALL plugin dll dependencies (and their dependencies, if any) need to live in the same folder as the plugin dll.

6. Add a new config section for your observer in FabricObserver/PackageRoot/Config/Settings.xml (see example at bottom of that file) Update ApplicationManifest.xml with Parameters if you want to support Versionless Application Parameter-only Upgrades for your plugin. (Look at both FabricObserver/PackageRoot/Config/Settings.xml and FabricObserverApp/ApplicationPackageRoot/ApplicationManifest.xml for several examples of how to do this.)

7. Ship it! (Well, test it first =)

If you want to build your own nupkg from FO source, then:

Open a PowerShell console, navigate to the top level directory of the FO repo (in this example, C:\Users\me\source\repos\service-fabric-observer):

cd C:\Users\me\source\repos\service-fabric-observer
./Build-FabricObserver
./Build-NugetPackages

The output from the above commands contains FabricObserver platform-specific nupkgs and a nupkg you have to use for plugin authoring named Microsoft.ServiceFabricApps.FabricObserver.Extensibility.3.3.0.nupkg. Nuget packages will be located in C:\Users\me\source\repos\service-fabric-observer\bin\release\FabricObserver\Nugets.