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Consider using route information instead of URL for Starlette transactions #833

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HenrikOssipoff opened this issue May 23, 2020 · 11 comments · Fixed by #957
Closed

Consider using route information instead of URL for Starlette transactions #833

HenrikOssipoff opened this issue May 23, 2020 · 11 comments · Fixed by #957

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@HenrikOssipoff
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HenrikOssipoff commented May 23, 2020

We're slowly started using Starlette for some smaller applications due to its simplicity and async capabilities. We also happen to use Elastic APM for our monitoring, but we've found that the agent works quite different from other agents, such as Django or Flask.

The default for Django, is "HTTP Method + path.to.view". This can be changed for Django 2.2+ using the django-transaction-name-from-route setting, to instead use the route that was matched against. For example GET /users/<int:user_id>/.

For Flask, the default seems to be the that of method + route, e.g.: GET /users/<int:user_id/.

For Starlette however, information about the matched route is not actually available on the request, and for that reason (I assume), the full URL is instead used as the transaction name.
In the example above, it would mean that every time a user with a different URL was hit, it would generate two separate transaction entries. For some of our views, that would mean 1+ milllion transaction names for the same view.

However, it is somewhat possible to extract the route by mimicking what Starlette itself does. On the request, the Application itself is available, and from that route router + routes. This means it's possible to loop over them, and match their regular expression against the current request.

  1. I realise this isn't pretty in any way, shape or form - but it would make instrumentation of Starlette applications a lot more useable
  2. I also realise it's backwards incompatible - but perhaps this could be solved in the same way that it's done with Django?

What would your thought be on such a change?

For us at our workplace, we've actually have one major of our main applications ported to Starlette, but once we saw what was happening to the transaction names, we had to revert the deployment. We'd love to have it running, so we'd probably be interested in providing a patch for it as well.

EDIT
Just wanted to add this here, since it's a discussion of making this type of information available in the middleware system: encode/starlette#685
It also links another repo for timing of ASGI that basically does what I describe here, by looping over all routes and comparing them to the current URL.

@HenrikOssipoff HenrikOssipoff changed the title Should the Starlette agent use route information instead of URL? Consider using route information instead of URL for Starlette transactions May 23, 2020
@basepi
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basepi commented May 26, 2020

The Starlette support is new enough I'd be willing to entertain a change like this. I would much rather have route information than the full path, but like you mentioned, it's unavailable without manually calculating the route. My only concern with that solution is that it adds some processing overhead. But I do think it would give us more useful transaction names, and hopefully they'll add an official way to get that information in middleware.

@HenrikOssipoff is this a change for which you'd be willing to open a PR?

@basepi basepi added the feature label May 26, 2020
@HenrikOssipoff
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@basepi Definitely, I'll give it a go in the near future. Would enable us to use Starlette much more than we currently do :)

@basepi
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basepi commented Oct 7, 2020

@HenrikOssipoff Is this a change you're still interested in contributing?

@BrikerMan
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BrikerMan commented Oct 18, 2020

@HenrikOssipoff Is this a change you're still interested in contributing?

@basepi There is a solution mentioned here tiangolo/fastapi#486 (comment), but it needs to iterate through all the routes for each request.

path = [route for route in request.scope['router'].routes if route.endpoint == request.scope['endpoint']][0].path

@basepi
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basepi commented Oct 19, 2020

Thanks. I think that's probably worthwhile overhead, the current implementation isn't super great.

@BrikerMan
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Thanks. I think that's probably worthwhile overhead, the current implementation isn't super great.

Can't wait for the new version. Maybe we can make it an optional choice via an env variable.

@basepi
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basepi commented Oct 20, 2020

I'm honestly still leaning towards just making the change without backwards compatibility considerations. The starlette support is very new and the current behavior could probably be considered a bug. Thoughts?

@BrikerMan
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I'm honestly still leaning towards just making the change without backwards compatibility considerations. The starlette support is very new and the current behavior could probably be considered a bug. Thoughts?

In my use case, I am happy to fix this one a bug. I don't need old behavior.

@beniwohli beniwohli self-assigned this Oct 21, 2020
@HenrikOssipoff
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@HenrikOssipoff Is this a change you're still interested in contributing?

Sorry very late to the game - I can see @beniwohli has assigned himself, which is more than fine by me. Work's not leaving me much free time unfortunately.

Looking forward to the "fix" though - sorry for being slow here.

Personally I would say you shouldn't think about backwards compatibility for this one, given most likely very few people even use this particular integration, but that's my opinion alone.

beniwohli added a commit to beniwohli/apm-agent-python that referenced this issue Oct 28, 2020
Unfortunately, we need to do some matching here that Starlette does
too, but currently isn't exposed. If/when encode/starlette#804
is merged, we can re-use the route from there.

closes elastic#833
@beniwohli
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@HenrikOssipoff I opened #957 with (hopefully) a fix for this. If you have time, would you mind giving that a quick spin and see if it works?

I agree that backwards compatibility is not a major concern. I would consider the current behavior as buggy compared to our other integrations.

@HenrikOssipoff
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@beniwohli Sweet I'll take it for a spin later tonight to test things out :)

beniwohli added a commit that referenced this issue Nov 17, 2020
* Starlette: use route name as transaction name if available

Unfortunately, we need to do some matching here that Starlette does
too, but currently isn't exposed. If/when encode/starlette#804
is merged, we can re-use the route from there.

closes #833

* detect trailing slash redirects from Starlette and give them a dedicated transaction name

* adapt original route for slash redirects
@basepi basepi added this to Planned in APM-Agents (OLD) via automation Nov 17, 2020
@basepi basepi moved this from Planned to Done in APM-Agents (OLD) Nov 17, 2020
beniwohli added a commit to beniwohli/apm-agent-python that referenced this issue Sep 14, 2021
* Starlette: use route name as transaction name if available

Unfortunately, we need to do some matching here that Starlette does
too, but currently isn't exposed. If/when encode/starlette#804
is merged, we can re-use the route from there.

closes elastic#833

* detect trailing slash redirects from Starlette and give them a dedicated transaction name

* adapt original route for slash redirects
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