Support HTTP2 healthchecks

Proposed Change

We have received requests for supporting HTTP/2 healthchecks in Diego. Currently, HTTP healthchecks are performed using HTTP/1.1, but some applications require HTTP/2.

Adding support for HTTP/2 healthchecks would require introducing a new property in the app manifest to specify that the healthcheck should use HTTP/2.

Proposed Change
Introduce a new property in the application manifest, such as:

health-check-http-version: http2

When this property is set, the healthcheck should be performed using HTTP/2 instead of HTTP/1.1.

Impact

• Apps handling healthchecks will need to be updated to support HTTP/2, if they specify it in the manifest
• Backward compatibility is maintained—if the property is not specified, the default will remain HTTP/1.1.

Acceptance criteria

I have an app that supports a http2 healthcheck
When i specify that I want a http2 healthcheck
Then a http2 healthcheck is perforemed

Related links

• https://github.com/cloudfoundry/healthcheck

No files, tests, or entry points are identified in the issue. Start by locating Diego's application-manifest parsing and existing HTTP/1.1 healthcheck handling, then determine how the new manifest property should select HTTP/2. Done means an app can request an HTTP/2 healthcheck while unspecified versions continue using HTTP/1.1, with coverage for both paths.