Is it possible to get the matched route in a intercepting feature. For metrics purposes it would be ...

# ktor

[jozefdransfield]

Is it possible to get the matched route in a intercepting feature. For metrics purposes it would be good if I could get /user/{name} not user/Jozef for response time metrics?

[Deactivated User]

Route has a toString method that you can use, or to help you see how to build your own string based on the tree:
https://github.com/ktorio/ktor/blob/0a45746af0db0457a6e1e988c27d9364cf064962/ktor-server/ktor-server-core/src/io/ktor/routing/Route.kt#L98

An interceptor for a route would look like this:
https://ktor.io/advanced/pipeline/route.html

There you have access to the Route node tree

[Deactivated User]

You can access to a Route from a call by casting the call to RoutingApolicationCall

I have updated the doc to reflect this: https://ktor.io/advanced/pipeline/route.html#route-from-call

[vonox7]

@Deactivated User i just tried casting it, but i get the following error:

java.lang.ClassCastException: io.ktor.server.jetty.JettyApplicationCall cannot be cast to io.ktor.routing.RoutingApplicationCall: Ljava/lang/ClassCastException;

[Deactivated User]

can you show the relevant code plz?

[vonox7]

https://gist.github.com/vonox7/2c61ca29cb059c67c101a4db092f5e03

Line 22 is always printing null, as the cast won’t succeed

[vonox7]

the same is with embeddedServer(Netty, ...)

[Deactivated User]

(I’m asking, and checking myself)

[Deactivated User]

but maybe you have to configure the phase to be explicitly after the Routing

[Deactivated User]

our using the event: Routing.RoutingCallFinished

(I’m checking)

[Deactivated User]

Maybe for your case, this would be better?

environment.monitor.subscribe(Routing.RoutingCallFinished) {
	println(it.route)
}

[Deactivated User]

because you are not intercepting a route like the link I put

[Deactivated User]

but trying to put a global interceptor

[vonox7]

Never saw the subscribe-api 😄
The thing is: I don’t get callbacks for this when the route did not match

[Deactivated User]

Mmm. I think with the other approach either if you plan to get the route.

Maybe you can do a mixed approach

[Deactivated User]

intercepting fallback

[Deactivated User]

+ event subscribing

[vonox7]

I’m logging all requests (request time and route) to analyze possible issues. An issue might be that the 95-percentile of a route is too high or that after a deployment the average count of non-matched routes gets too high

[vonox7]

Are there some docs to read for “intercepting fallback”?

[Deactivated User]

fun Application.registerMyRouteLogging() {
    fun log(path: String, handled: Boolean) {
        println("path=$path, handled=$handled")
    }

    environment.monitor.subscribe(Routing.RoutingCallFinished) { routingApplicationCall ->
        log(routingApplicationCall.route.toString(), handled = true)
    }
    intercept(ApplicationCallPipeline.Fallback) {
        log(call.request.uri, handled = false)
    }
}

[vonox7]

Ok, but one problem with this approach is that i can’t log the processing time of the routing-handler…

[Deactivated User]

Yes, you can. 1 sec

[Deactivated User]

val StartTimeAttribute = AttributeKey<Long>("StartTimeAttribute")

fun Application.registerMyRouteLogging() {
    fun log(call: ApplicationCall, path: String, handled: Boolean) {
        val elapsedTime = System.currentTimeMillis() - call.attributes[StartTimeAttribute]
        println("path=$path, handled=$handled, elapsedTime=$elapsedTime")
    }

    intercept(ApplicationCallPipeline.Infrastructure) {
        call.attributes.put(StartTimeAttribute, System.currentTimeMillis())
    }

    environment.monitor.subscribe(Routing.RoutingCallFinished) { call ->
        log(call, call.route.toString(), handled = true)
    }
    intercept(ApplicationCallPipeline.Fallback) {
        log(call, call.request.uri, handled = false)
    }
}

[Deactivated User]

I guess it should be nice to update the Metrics feature:

https://ktor.io/features/metrics.html

to allow to configure it to measure final urls, routing urls, or both

[Deactivated User]

in fact

[Deactivated User]

I think it already does what you want

[Deactivated User]

https://github.com/ktorio/ktor/blob/master/ktor-features/ktor-metrics/src/io/ktor/metrics/Metrics.kt

[vonox7]

Wow, thanks, thats a very clean solution! Seems like I don’t understand the 3 phases of the application very much. Maybe you could create a small chart when what Phase is triggered? For me it seems that the Fallback-Phase is always triggered:

path=/route/one/(method:GET), handled=true, elapsedTime=84
path=/route/one, handled=false, elapsedTime=84

[Deactivated User]

First infrastructure, then call, then fallback in order until the call has been processed, usually that happens in call, but the fallback can also resolve it, (for example the StatusPages feature)

[Deactivated User]

still, can’t you use the Metrics feature?

[Deactivated User]

from what you said, it seems that it is what you are trying to do, and it is already done

[Deactivated User]

if you miss something, we can add it

[vonox7]

I already took a look into the Metrics feature, but I think I haven’t understood the power of it and the extensibility (“Other reporters” section).

[Deactivated User]

what do you need?

[Deactivated User]

printing to the terminal?

[Deactivated User]

where are you sending the reportS?

[vonox7]

I’m sending the data to an InfluxDb where I analyze the data with Grafana

[vonox7]

But it seems that creating a custom reporter is the way to go, thank you!

[Deactivated User]

and you are sending raw requests, right?

[Deactivated User]

okay

[vonox7]

yes