What is a watchdog
A watchdog is a service that monitor other services and take actions when it detect a service is failing.
ASP.NET starting from Core 5 has a built in UI module to monitor other services, and in few line of code you can build a watchdog for your services.
How to hook it up with your services:
Your microservices should implement health check endpoints to be monitored by the orchestration service (Kubernetes, docker storm, … etc).
I explained in previous post on how to use built-in ASP.NET health check features to achieve build these endpoints.
I recommend reading that article because there I talked about the Microsoft package AspNetCore.Diagnostics.HealthChecks. This package contains all the middleware for build-in health checks, and as well in the same repository has a UI module that with few line of code build a UI to monitor all integrated services and monitor their health check endpoints.
How to use the UI module to build the monitoring service.
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Create a MVC application using
1 dotnet new mvc -n watchdog -
Add required packages:
1 dotnet add package AspNetCore.HealthChecks.UI -
define in appsettings.json all the services that you want to monitor. the format of the config section is as follows:
1 // Configuration 2 { 3 "HealthChecksUI": { 4 "HealthChecks": [ 5 { 6 "Name": "Ordering HTTP Check", 7 "Uri": "http://host.docker.internal:5102/hc" 8 }, 9 { 10 "Name": "Ordering HTTP Background Check", 11 "Uri": "http://host.docker.internal:5111/hc" 12 }, 13 //... 14 ]} 15 }In reality when we deploy the application to AKS or any service-mesh service, we need to replace the url address. But now we are just describing the idea of the UI module.
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add HealthCheckUI service
1builder.Services..AddHealthChecksUI()
2 .AddInMemoryStorage();
3
4// ....
5var app = builder.Build();
6// ....
7
8// the URL /hc-ui will display the user interface
9app.UseHealthChecksUI(config => config.UIPath = "/hc-ui");
When you run the application you will see the user interface that looks like
I am going to add more on monitoring services using other built-in features, so keep following me.