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Fix ASGIGetter keys to fetch from actual carrier headers #1435
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We just hit this same problem, not in GCP, and it's forcing us to downgrade to 0.34b0. We applied this patch manually to 0.35b0 and it also worked for us. |
Sorry, which |
Ah sorry @ocelotl, I meant the |
# Conflicts: # CHANGELOG.md
# Conflicts: # CHANGELOG.md
@ocelotl is this PR something you can help with reviewing? Or maybe @rogersd @srikanthccv, as I've seen you working in the ASGI area recently? Sorry for the wide ping, it just feels to me like an easy fix for a bug that can become quite common and important. |
@@ -260,7 +260,8 @@ def get( | |||
return decoded | |||
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def keys(self, carrier: dict) -> typing.List[str]: | |||
return [_key.decode("utf8") for (_key, _value) in carrier] | |||
headers = carrier.get("headers") or [] |
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Just curious, if "headers"
is not in carrier.keys
, shouldn't this method return [_key.decode("utf8") for (_key, _value) in carrier]
. The way this is being modified makes this method return an empty list if "headers"
is not in carrier.keys
.
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Considering the .get()
method above returns header-specific fields and its description mentions "header name in scope"
, I assumed here we'd only want to return headers rather than the whole carrier, which in this case is the ASGI scope. I'm not too sure fetching all values from the scope is correct though, there's a bunch of ASGI-specific info there and I wouldn't expect to see (nor inject) any extra info from Opentelemetry.
Now that you mention it though, I guess some people may be relying on this behaviour now, so maybe we should join both lists? Or would we treat this as a breaking change instead?
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I would argue that this should be keyed to headers, but we do need to be conscious of other formats. For example as we look through most proprogators, the common use is for the carrier to only contain header keys. The most relatable part of the spec docs are here.
https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/context/api-propagators.md#:~:text=In%20order%20to%20increase%20compatibility%2C
The carrier of propagated data on both the client (injector) and server (extractor) side is usually an HTTP request. In order to increase compatibility, the key/value pairs MUST only consist of US-ASCII characters that make up valid HTTP header fields as per [RFC 7230](https://tools.ietf.org/html/rfc7230#section-3.2).
The http request will have other keys with it such as client, method, query params etc which we dont care about, we only need the headers. It is only the TextMapPropagator section that states the carrier is usually a http request though even though that does seem to be the standard to supply the http payload as a carrier. As we look at the spec on proprogators, It actually doesn't specify whats in a carrier. Which is here https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/context/api-propagators.md#carrier
In the branch i was going to make a pull request against i searched for the headers key first and iderated over that only, and if that did not exist, I chose the carrier payload as it should then be a header.
The argument could be made that we need to look through the entire carrier payload for headers, as the format of carrier has not been specified. But it feels burdensome for this method to have to deal with that.
Lastly
The above pull request would also fail on line 264 when a header isn't a byte type so it is still broken. I had a pull request i was going to submit but im not a contributor. how would you like me to submit the proposed change?
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As far as this processor is concerned, it has been working until this change. The previous behaviour was not correct either, but at least it would not crash. The changes in this PR directly address the main issue, which is the crash due to iterating the wrong value, and fetching the correct value the same way we do in .get()
. I would argue that any more changes in the behaviour than that are out of scope and probably require a separate discussion and investigation. In any case, something for the maintainers to decide CC @ocelotl @srikanthccv
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I think this is a correct fix both for the crash and behaviour because the web framework instrumentation may receive carriers of different types, but their goal is to inject/extract the trace context information into the HTTP header, which is used for propagation. And since the ASGI specification says the headers
is Iterable[[byte string, byte string]]
I think it's safe to assume keys will be a byte string so it's not broken.
# Conflicts: # CHANGELOG.md
@ocelotl @rogersd @srikanthccv @shalevr sorry for the wide ping again, just wanted to give another nudge as it's been a few weeks since I first opened the PR. A review with improvements would be appreciated in order to get this closer to approval. Thanks. |
I will take a look at it. |
set_global_textmap(MockTextMapPropagator()) | ||
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def tearDown(self): | ||
set_global_textmap(self.previous_propagator) |
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I couldn't follow what the tests were targeting. I would test that ASGIGetter
instance doesn't throw an exception for scope dict, which is currently failing, and additionally assert that keys return the Headers keys.
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The idea was to ensure that the values returned by get()
and keys()
were the same and they were consistent across different tests, but it was a bit of a hack indeed with that custom propagator. I added simpler tests in test_getter.py
instead that indeed fail before the fix and pass now, hope they make sense c219bb0
This reverts commit afcf3c5.
# Conflicts: # CHANGELOG.md
Assuming the current github workflow checks pass and the PR is merged, when do the maintainers expect a release that has this included to be released? |
A periodic monthly release is happening this week (or early next week). |
@srikanthccv I had to update the branch with changes from |
Hello @srikanthccv, unless I'm mistaken this has not been released yet right? Any chance this gets bumped as it's a bit of a challenge without this fix out. Thanks :) |
afaik it's not been released indeed, last published version seems to be v0.36b0, which still contains the incorrect behaviour. In case it helps, while no new version is out, in our repos we have temporarily addressed it by overriding the default from opentelemetry.instrumentation import asgi
class ASGIGetter(asgi.ASGIGetter):
"""
Override default getter implementation while `.keys()` fix is not out
https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1435
"""
def keys(self, carrier: dict[str, typing.Any]) -> list[str]:
headers = carrier.get("headers") or []
return [_key.decode("utf8") for (_key, _value) in headers]
def setup_tracing() -> None:
# Override default asgi_getter while `.keys()` fix is not out
# https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1435
asgi.asgi_getter = ASGIGetter()
... |
Thanks @hasier A sound proposal that I'll have to review. I'm not using the ASGI extension directly but through FastAPI. Cheers. |
Is this fix already merged @hasier ? |
@theobouwman the fix was merged on January 12 and included as part of Version 1.16.0/0.37b0 |
Description
Working in ASGI with any propagator using
getter.keys()
, e.g. the GCP propagator when no header is present in a request, it breaks with the below message:In my case, this seems to be triggered by the fact that the GCP propagator uses
getter.keys()
as a fallback. Thiskeys()
function in theASGIGetter
seems to be taking the header values from an incorrect place, and therefore provoking the crash. I found it with the GCP example, but it's probably affecting others, as the issue lays with the definition ofASGIGetter.keys()
here.Fixes #1487
Type of change
How Has This Been Tested?
Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration
getter.keys()
on an ASGI context makes the request fail. It's easy to reproduce with the GCPCloudTraceFormatPropagator
when the request does not have ax-cloud-trace-context
header.NOTE: I've re-created
opentelemetry.test.mock_textmap.MockTextMapPropagator
with a tiny modification to usekeys()
from thegetter
. I understand it might be interesting to add these changes to the original testing repo as well, as it ensures all keys that.get()
returns are in.keys()
as well, but thought it'd be interesting to have this fix out soon and then potentially port it there if it seemed useful/appropriate to y'all.Does This PR Require a Core Repo Change?
Yes. - Link to PR:Checklist:
See contributing.md for styleguide, changelog guidelines, and more.
Documentation has been updated