Add endpoint support for web-specific stack

[spencergibb]

In spring cloud there are numerous MvcEndpoints that took advantage of the ability of SpringMVC to add arbitrarily complex behaviors to the actuator such as:

• complex POST parameters (maps & objects)
• wrapping a servlet (/hystrix.stream), basically access to raw HttpServletRequest & HttpServletResponse

The benefit of having them in actuator is that they aren't part of the main application and can be protected by actuator security.

If we move them to normal endpoints we would lose all of the benefits of actuator (global disabled, security, management port, etc...) that are users are used to.

Thoughts?

[snicoll]

The end goal of the endpoint infrastructure in 2.0 is not to replicate what Spring MVC can do (imagine the work to abstract that to webflux and Jersey). If you have those needs you need to keep your MVC controllers as they are today.

We still need to work on letting users define whatever they like using a traditional controller (and with that limitation in mind). Several things:

• If you register your controller in a @ManagementContextConfiguration it will be part of the actuator application context (if one). This isn't new and documented
• We have @ConditionalOnEnabledEndpoint that currently only works when set on an endpoint or an extension. We probably need to relax that a bit for that scenario

I am happy to discuss alternative routes but your endpoint needs to be an endpoint in the first place. I would argue that the second example is not an endpoint: where is the JMX feature with a method that takes servlet and response? How do you pass those complex map and objects with JMX for the first case?

On our side, we did move Jolokia because we realized it wasn't an endpoint. I believe you should do the same.

[wilkinsona]

For the security aspect of this, we now have the same problem with our Jolokia support. Whatever is figured out for that will, hopefully, be relevant to Spring Cloud as well.

[spencergibb]

Regarding @ManagementContextConfiguration it puts it in the management application context, but not the web (/application) context. Currently, that has to be done by hand.

[wilkinsona]

This doesn't appear to be moving much. @spencergibb Have you reviewed your current endpoints to determine which of them aren't really endpoints? What, if anything, do you still need to help you to make the transition?

[spencergibb]

There are a few. In some cases I changed ids from /bus/refresh to /bus-refresh. Other cases we've simplified (removed complex input). Some cases I moved request parameters to a path parameter. The hystrix servlet, I copied the jolokia management auto-configuration. I think we're ok writing mvc controllers, etc... where it doesn't fit. The one thing missing is disabling the non @Endpoints when all endpoints are disabled.