Fix ASGIGetter keys to fetch from actual carrier headers #1435

hasier · 2022-11-10T13:10:46Z

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:

Traceback (most recent call last):
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/uvicorn/protocols/http/httptools_impl.py", line 404, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/uvicorn/middleware/proxy_headers.py", line 78, in __call__
    return await self.app(scope, receive, send)
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/fastapi/applications.py", line 270, in __call__
    await super().__call__(scope, receive, send)
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/starlette/applications.py", line 124, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/starlette/middleware/errors.py", line 184, in __call__
    raise exc
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/starlette/middleware/errors.py", line 162, in __call__
    await self.app(scope, receive, _send)
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/opentelemetry/instrumentation/asgi/__init__.py", line 531, in __call__
    span, token = _start_internal_or_server_span(
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/opentelemetry/instrumentation/utils.py", line 111, in _start_internal_or_server_span
    ctx = extract(context_carrier, getter=context_getter)
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/opentelemetry/propagate/__init__.py", line 102, in extract
    return get_global_textmap().extract(carrier, context, getter=getter)
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/opentelemetry/propagators/composite.py", line 52, in extract
    context = propagator.extract(carrier, context, getter=getter)
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/opentelemetry/propagators/cloud_trace_propagator/__init__.py", line 94, in extract
    header = self._get_header_value(getter, carrier)
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/opentelemetry/propagators/cloud_trace_propagator/__init__.py", line 78, in _get_header_value
    for key in getter.keys(carrier):
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/opentelemetry/instrumentation/asgi/__init__.py", line 263, in keys
    return [_key.decode("utf8") for (_key, _value) in carrier]
  File "/root/.cache/pypoetry/virtualenvs/api-9TtSrW0h-py3.10/lib/python3.10/site-packages/opentelemetry/instrumentation/asgi/__init__.py", line 263, in <listcomp>
    return [_key.decode("utf8") for (_key, _value) in carrier]
ValueError: too many values to unpack (expected 2)

In my case, this seems to be triggered by the fact that the GCP propagator uses getter.keys() as a fallback. This keys() function in the ASGIGetter 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 of ASGIGetter.keys() here.

Fixes #1487

Type of change

Bug fix (non-breaking change which fixes an issue)

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

Using any propagator that makes use of getter.keys() on an ASGI context makes the request fail. It's easy to reproduce with the GCP CloudTraceFormatPropagator when the request does not have a x-cloud-trace-context header.
The added test changes make tests fail if the fix is not included.

NOTE: I've re-created opentelemetry.test.mock_textmap.MockTextMapPropagator with a tiny modification to use keys() from the getter. 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:~~
No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

Followed the style guidelines of this project
Changelogs have been updated
Unit tests have been added
~~Documentation has been updated~~

linux-foundation-easycla · 2022-11-10T13:10:49Z

The committers listed above are authorized under a signed CLA.

✅ login: hasier (a0b4c4f, afcf3c5, e4dbc51)

bluesliverx · 2022-11-15T23:19:08Z

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.

ocelotl · 2022-11-21T15:11:04Z

gcp/src/opentelemetry/propagators/cloud_trace_propagator/init.py#L78). This all() call in the ASGIGetter seems to be taking the header values from an incorrect place, and therefore provoking the crash.

Sorry, which all() call?

hasier · 2022-11-21T15:35:47Z

gcp/src/opentelemetry/propagators/cloud_trace_propagator/init.py#L78). This all() call in the ASGIGetter seems to be taking the header values from an incorrect place, and therefore provoking the crash.

Sorry, which all() call?

Ah sorry @ocelotl, I meant the keys() function, just updated the description 🙏

# Conflicts: # CHANGELOG.md

hasier · 2022-11-28T17:57:55Z

@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.

ocelotl · 2022-11-28T19:51:18Z

...tation/opentelemetry-instrumentation-asgi/src/opentelemetry/instrumentation/asgi/__init__.py

@@ -260,7 +260,8 @@ def get(
        return decoded

    def keys(self, carrier: dict) -> typing.List[str]:
-        return [_key.decode("utf8") for (_key, _value) in carrier]
+        headers = carrier.get("headers") or []


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.

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?

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?

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

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

hasier · 2023-01-10T11:17:06Z

@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.

srikanthccv · 2023-01-10T14:19:52Z

I will take a look at it.

srikanthccv · 2023-01-10T20:11:32Z

instrumentation/opentelemetry-instrumentation-asgi/tests/test_asgi_custom_headers.py

+        set_global_textmap(MockTextMapPropagator())
+
+    def tearDown(self):
+        set_global_textmap(self.previous_propagator)


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.

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

cipherself · 2023-01-11T14:14:45Z

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?

srikanthccv · 2023-01-11T14:36:56Z

A periodic monthly release is happening this week (or early next week).

hasier · 2023-01-12T16:20:03Z

@srikanthccv I had to update the branch with changes from main, please re-approve and merge whenever you have a few mins, as I don't have permissions to do so as a first-time contributor 😊🙏

…try#1435)

Lawouach · 2023-02-09T09:24:24Z

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 :)

hasier · 2023-02-09T12:51:58Z

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 asgi getter.

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()
    ...

Lawouach · 2023-02-09T13:01:51Z

Thanks @hasier

A sound proposal that I'll have to review. I'm not using the ASGI extension directly but through FastAPI. Cheers.

theobouwman · 2023-11-04T12:22:54Z

Is this fix already merged @hasier ?

hasier · 2023-11-06T10:54:12Z

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

hasier added 2 commits November 10, 2022 11:48

Fix generating ASGI keys

a0b4c4f

Test fix generating ASGI keys

afcf3c5

hasier requested a review from a team as a code owner November 10, 2022 13:10

Update CHANGELOG.md

e4dbc51

hasier added 2 commits November 21, 2022 15:56

Merge branch 'main' into fix-asgi-keys

efff3af

# Conflicts: # CHANGELOG.md

Merge branch 'main' into fix-asgi-keys

7d1e9ab

# Conflicts: # CHANGELOG.md

Merge branch 'main' into fix-asgi-keys

a7b648f

ocelotl reviewed Nov 28, 2022

View reviewed changes

Merge branch 'main' into fix-asgi-keys

b4e51cc

hasier requested a review from ocelotl December 13, 2022 12:26

kartoch mentioned this pull request Dec 14, 2022

ASGI Instrumentation ValueError: too many values to unpack (expected 2) during JaegerPropagator #1487

Closed

ncbraner mentioned this pull request Dec 19, 2022

Update keys() to be able to iterate over a dict by updating the loop … #1492

Open

2 tasks

Merge branch 'main' into fix-asgi-keys

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# Conflicts: # CHANGELOG.md

srikanthccv self-assigned this Jan 10, 2023

Merge branch 'main' into fix-asgi-keys

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srikanthccv reviewed Jan 10, 2023

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hasier added 2 commits January 11, 2023 10:33

Revert "Test fix generating ASGI keys"

5980395

This reverts commit afcf3c5.

Add getter keys() tests

c219bb0

srikanthccv approved these changes Jan 11, 2023

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Merge branch 'main' into fix-asgi-keys

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# Conflicts: # CHANGELOG.md

Merge branch 'main' into fix-asgi-keys

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srikanthccv enabled auto-merge (squash) January 12, 2023 16:34

Merge branch 'main' into fix-asgi-keys

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srikanthccv merged commit 092d8c8 into open-telemetry:main Jan 12, 2023

hasier deleted the fix-asgi-keys branch January 13, 2023 09:56

james-emerton pushed a commit to james-emerton/opentelemetry-python-contrib that referenced this pull request Jan 19, 2023

Fix ASGIGetter keys to fetch from actual carrier headers (open-teleme…

f16f059

…try#1435)

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Fix ASGIGetter keys to fetch from actual carrier headers #1435

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Fix ASGIGetter keys to fetch from actual carrier headers #1435

Fix ASGIGetter keys to fetch from actual carrier headers #1435

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Description

Type of change

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Does This PR Require a Core Repo Change?

Checklist:

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