AspNetCore.Diagnostics.CachedHealthChecks

This lib is an extension built on top of the Microsoft.Extensions.Diagnostics.HealthChecks.HealthCheckService that allows the developer to choose to cache any checks they want.

Installation

To install this lib, simply install the package from NuGet using the command below.

Install-Package AspNetCore.Diagnostics.CachedHealthChecks

How To Use

To use the lib is very simple. First you need to add the service to the collection. To do so, use the services.AddHealthChecks() overload that contains the cache setup. With the service in place, call .EnableCache() right after the check registration.

    services.AddHealthChecks(options =>
        {
            options.DefaultCacheDuration = TimeSpan.FromMinutes(10);
            options.Tag = "cacheable";
            options.CacheExceptions = false;
            options.CachedExceptionsDuration = null;
        })
        .Add(registration).EnableCache();

In the example above, I used .Add() but the extension will work with any third party check library, like the awesome AspNetCore.Diagnostics.HealthChecks.

AddHealthChecks Setup

When calling the services.AddHealthChecks() overload, you can provide some options to the service. The options are described below.

Option	Description	Default
Tag	The tag used to identify cacheable registrations	"cacheable"
CachePrefix	The prefix to use when caching a registration report	"cacheable-hc-"
DefaultCacheDuration	The default cache duration	10 minutes
CacheExceptions	Indicate if checks that throw exceptions should be cached	false
CachedExceptionsDuration	When CacheExceptions is true, the checks that throw exception will be cached using this duration. If none is provided, DefaultCacheDuration will be used.	null

EnableCache Setup

When calling .EnableCache() you can provide some options, but it is up to you. You can call it with no arguments and simply use the ones provided above.

Option	Description	Default
CacheDuration	When provided, will override the DefaultCacheDuration for a single registration.	null
ExceptionCacheDuration	When provided, will override the CachedExceptionsDuration for a single registration.	null

How Does The Lib Work

The lib replaces the DefaultHealthCheckService provided by Microsoft and inject its own, called CacheableHealthCheckService. This new service was largely based on the default implementation, so you can expect the exact same behavior, with one exception, you can now cache responses.

When you call .EnableCache() after a registration, the lib adds a tag cacheable to the list of tags for it. You can change this tag using the options if you think you may collide with this one.

When the health check enpoint is called, the lib invokes the predicate you registered when you called app.UseHealthChecks(), so it takes precedence over cached responses.

When the service finds a registration with the specific tag, it adds a message to its data dictionary and add it to the cache. Next time the endpoint is called, the cached response will be reported and the health check will not be run until it expires.

The cache is done using an instance of the IMemoryCache and the key to the cache is built using the CachePrefix and registration name.

Note: Only registrations with the specific tag will be cached. This means that you can have health checks that don't get cached side by side with one that is and one will not affect the other.

Want to contribute

If you find bugs and don't have time to submit a PR, please report it using the github isses. On the other hand, if you can submit a PR I'll gladly take a look at it.