* Use options for registering health checks
This change pivots to use options for registering health checks. We get
a few pretty nice things out of this, and it unblocks some of our
requirements.
Now all registration methods support the application developer
configuring the name, failure-status, and tags for each health check.
This is a requirment, that we weren't really satisfying - which is what
led to this redesign. In support of this health checks now return pass/fail,
and the service is responsible for assigning the status.
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Health check authors that need configuration data (connection string as
an example) now have three ways to do this depending on their
requirements.
1. Create an instance and register that (easiest)
2. Use Type Activation and pass parameters (middle)
3. Use named options (richest)
We expect most health checks to need/want some kind of configuration -
which 1) works pretty well to solve. However many other health checks
will need DI + configuration. It was also a gap that we didn't have a
good way to use named options, when it's such a good fit for our
scenarios.
Added new registration methods for type activation that allow you to
pass parameters for 2).
Added a context type that allows the running health check access to its
registration for 3).
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Redesigned and renamed how status gets reported. Health checks return
pass/fail result, but the overall HealthReport includes entries of a
different type. This seems fine because there isn't really a way to
consume a HealthCheckResult directly - the service is the only consumer.
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Added support for tags. This was easy to add now that we have a separate
registration type, and it's quite handy for building filters (see
sample).
* HARDER BETTER STRONGER FASTER
* Allow health checks to use any DI lifetime
This change allows registered IHealthCheck implementations to use any DI
lifetime. This is necessary for scenarios like using EF which requires a
scope.
The works by having the health check service create a scope for each
time it queries health checks. This scope does not overlap or share
state with other scopes (the request scope) so there is no crosstalk
between processing going on per-request in ASP.NET Core and the health
check operation.
* PR feedback and some logging cleanup
* Remove JSON output and convert to sample
GlennC and I made the decisison to turn the JSON output into a sample
rather than something we support out of the box. We wouldn't tell
customers to definitely use it and we don't want to introduce more
coupling to JSON.NET.
This allows each middleware to be configured with a specific set of
checks (by name). See the comments in the sample for how this is
frequently used.
This is also addresses aspnet/Home#2575 - or at least the part that we
plan to do. We think that any sort of built-in system of metadata or
tags is vast overkill, and doesn't really align with the primary usage
of health checks.
We're providing building blocks, and these can be put together to
build more complicated things like what's described in aspnet/Home#2575.
Ryan Nowak
Zhiliang
martincostello
Ryan Nowak