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Reimplement the keys method in WSGI CarrierGetter #379

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merged 3 commits into from
Mar 25, 2021
Merged

Reimplement the keys method in WSGI CarrierGetter #379

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5eb6174
Reimplement the keys method in WSGI CarrierGetter
Mar 25, 2021
427c2c6
Update CHANGELOG.md accordingly
Mar 25, 2021
164b247
Merge branch 'main' into wsgi-carrier-keys
Mar 25, 2021
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2 changes: 2 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
([#364](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/364))
- `opentelemetry-propagator-ot-trace` Do not throw an exception when headers are not present
([#378](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/378))
- `opentelemetry-instrumentation-wsgi` Reimplement `keys` method to return actual keys from the carrier instead of an empty list.
([#379](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/379))

### Changed
- Rename `IdsGenerator` to `IdGenerator`
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8 changes: 7 additions & 1 deletion ...ion/opentelemetry-instrumentation-wsgi/src/opentelemetry/instrumentation/wsgi/__init__.py
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Expand Up @@ -66,6 +66,8 @@ def hello():
from opentelemetry.trace.status import Status, StatusCode

_HTTP_VERSION_PREFIX = "HTTP/"
_CARRIER_KEY_PREFIX = "HTTP_"
_CARRIER_KEY_PREFIX_LEN = len(_CARRIER_KEY_PREFIX)


class CarrierGetter(DictGetter):
Expand All @@ -89,7 +91,11 @@ def get(
return None

def keys(self, carrier):
return []
return [
key[_CARRIER_KEY_PREFIX_LEN:].lower().replace("_", "-")
for key in carrier
if key.startswith(_CARRIER_KEY_PREFIX)
]
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Out of curiosity, did this prevent or limit propagation in some way when it was implemented as an empty list?

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@marcinzaremba marcinzaremba Mar 25, 2021 •
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It prevents any use case when information to be extracted is not known beforehand (for example HTTP headers starting with a particular prefix, but with unknown exact names). The great example is OT Trace Propagator, where the current implementation (empty list) renders injecting baggage unusable:

opentelemetry-python-contrib/propagator/opentelemetry-propagator-ot-trace/src/opentelemetry/propagators/ot_trace/__init__.py

Line 92 in f8e51c4

for key in getter.keys(carrier):

On the other hand when carrier would be manipulated directly, it would shift a specific implementation of keys translation (from uppercase, environ-like WSGI format) to every consumer.

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The great example is OT Trace Propagator, where the current implementation (empty list) renders injecting baggage unusable:

Thanks. This is what I was interested in.



carrier_getter = CarrierGetter()
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17 changes: 16 additions & 1 deletion instrumentation/opentelemetry-instrumentation-wsgi/tests/test_getter.py
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Expand Up @@ -22,15 +22,30 @@ def test_get_none(self):
getter = CarrierGetter()
carrier = {}
val = getter.get(carrier, "test")

self.assertIsNone(val)

def test_get_(self):
def test_get(self):
getter = CarrierGetter()
carrier = {"HTTP_TEST_KEY": "val"}
val = getter.get(carrier, "test-key")

self.assertEqual(val, ["val"])

def test_keys(self):
getter = CarrierGetter()
keys = getter.keys(
{
"HTTP_TEST_KEY": "val",
"HTTP_OTHER_KEY": 42,
"NON_HTTP_KEY": "val",
}
)

self.assertEqual(keys, ["test-key", "other-key"])

def test_keys_empty(self):
getter = CarrierGetter()
keys = getter.keys({})

self.assertEqual(keys, [])