disable tracing for healthchecks

[replay]

I'm not sure what the best method to disable tracing on certain routes is. We could also just have a list of urls where tracing should be disabled, then we could compare the url against that list in api/middleware/tracer.go, but I think maintaining such a list is going to be ugly.

We could also just not add the tracer middleware with r.Use() anymore, but add it in those routes that should have tracing enabled separately, but then we wouldn't have the tracer in all the middlewares that get executed before that one because then the tracer would be later in the list of middlewares.

[Dieterbe]

why do all the work up to here if we don't need tracing? can't we do this at the start of this function?

[replay]

in the beginning of this function macCtx.Data["noTrace"] would not have been set yet, because the tracer is at the beginning of the list of handlers before the one that sets noTrace. I think it probably makes sense to leave the tracer at it's position in the middleware chain, so that we have it available in the other middlewares if we want to use it there.

[replay]

Tested like this:

• Built MT image from this branch
• Brought up docker-dev-custom-cfg-kafka
• Called curl -H 'X-Org-Id: 1' http://localhost:6060/render -H 'Content-Type: application/json' -d '{"target": ["*"]}', received expected response []
• Checked Jaeger and saw a trace for the above /render call
• Called curl -H 'X-Org-Id: 1' http://localhost:6060/node, received expected response
• Checked Jaeger and verified that there is no new trace for the call to /node
• Called curl -H 'X-Org-Id: 1' http://localhost:6060, received expected response OK
• Checked Jaeger again and verified that there's no new trace for the above call
• Called curl -H 'X-Org-Id: 1' http://localhost:6060/cluster, got expected response
• Checked Jaeger to verify that there is a trace for the /cluster call

Looks good afaict

[Dieterbe]

great. thanks mauro!