Feat: Add EventToCarrier to AWS Lambda semantic conventions #164

rapphil · 2023-07-06T04:46:21Z

This PR is an attempt to create a long term solution for addressing this issue that is affecting the opentelemetry-lambda: open-telemetry/opentelemetry-lambda#714

This PR:

Introduces the EventToCarrier entity, that allows you to convert a lambda event into a carrier to be used in TextMapPropagators to extract the context.
Proposes an environment variable OTEL_AWS_LAMBDA_EVENT_TO_CARRIERS to be used in lambdas to control what EventToCarriers should be used in the lifecycle of a lambda.

ps.: I decided to remove the span links because they were only inserted as workaround for the problem of not being possible to use different context propagation mechanisms. I'm open to discussing adding it back with a more configurable behaviour.

There is a proof of concept java implementation in this PR: rapphil/opentelemetry-java-instrumentation#1 (I'm not creating a PR against the otel repo to reduce the noise).

Signed-off-by: Raphael Silva <[email protected]>

Oberon00 · 2023-07-06T08:20:46Z

specification/faas/aws-lambda.md


-[Span Link]: https://opentelemetry.io/docs/concepts/signals/traces/#span-links
+The `EventToCarrier` MUST implement the `Convert` operation to convert a lammbda `Event` into a `Carrier`.


This EventToCarrier sounds like an ordinary getter function that can be passed to the propagator along with the carrier. And in fact that is how it is implemented in some places, e.g. see .NET https://github.com/open-telemetry/opentelemetry-dotnet-contrib/blob/Instrumentation.AWSLambda-1.1.0-beta.3/src/OpenTelemetry.Instrumentation.AWSLambda/Implementation/AWSLambdaUtils.cs#L68-L95

So I would suggest to change the wording here to avoid introducing this new intermediate concept.

I disagree. The linked .NET implementation does not appear to be user-provided and thus does not account for any event type not known to the instrumentation. It also does not provide a mechanism for extracting context information from any source other than the specific sources it has implemented. Because it combines the context propagation and event processing it does not provide any opportunity for composition to enable the user to establish a chain of responsibility. In fact, it's not at all implemented as an ordinary getter function that can be passed to a propagator, it is a sealed context extraction mechanism with limited knowledge of how to process a few event types.

This PR is also not proposing anything user-configurable beyond the sealed list of strings. If it does, please clarify the wording, or point me to where I missed it.

(Regarding the particular linked instrumentation, a custom context can be extracted by the user and then passed explicitly https://github.com/open-telemetry/opentelemetry-dotnet-contrib/blob/Instrumentation.AWSLambda-1.1.0-beta.3/src/OpenTelemetry.Instrumentation.AWSLambda/AWSLambdaWrapper.cs#L97 which is much simpler to use, implement & understand in this case (but of course the concept would not be applicable to fully automatic / agent based instrumentations).)

In the new revision I tried to make it clear that the EventToCarrier is configurable.

Oberon00 · 2023-07-06T08:25:37Z

specification/faas/aws-lambda.md

+* `http_headers` = populates the `Carrier` with the content of the http headers.
+* `sqs` - populate the carrier with the content of the `AWSTraceHeader` system attribute of the message.


This is a bit unclear/inconsistent. For the HTTP headers, you would also have the headers like traceparent, etc. available that may be usable with propagators other than X-Ray. For SQS you specify only the system attributes, which will only contain X-Ray.

Agreed, extracting a carrier from an SQS event should probably include both message attributes and message system attributes.

I removed the list of pre defined EventToCarrier from the new revision.

Oberon00 · 2023-07-06T08:29:13Z

specification/faas/aws-lambda.md

+
+Valid values to configure the composite `EventToCarrier` are:
+
+* `lambda_runtime` - populates the `Carrier` with a key `X-Amzn-Trace-Id` from the value of the `_X_AMZN_TRACE_ID` environment variable. (see note below)


I think there is actually no need to have a per-trigger-type distinction, since most functions will only have a single trigger type anyway. I think instead there are 3 things for which it may make sense to switch them on/off separately:

Propagation using X-Ray from _X_AMZN_TRACE_ID (or equivalent Java sytem property)

Propagation using X-Ray information in event payload (e.g. SQS system attributes, HTTP headers)

Propagation using the default / configured propagator using sensible locations in the event payload (e.g. SQS message attributes, SNS message attributes, HTTP headers)

This is not a per-trigger-type distinction, this is enumerating a set of pre-defined implementations of the EventToCarrier abstraction that can be selected at runtime.

As for the three toggles you propose, two and three are the same thing as long as a carrier can be extracted from the event and handed to the configured propagator. One is also effectively the same to the extent that an EventToCarrier implementation can always choose to include information in the carrier that was not in the incoming event but instead extracted from the operating environment or some other source.

The whole point of this is to separate the "Propagation using " from the second half of each of those sentences and to give the user the controls they need to choose what works best for them. We don't need to choose only three options for the user.

Please note that in all Lambda instrumentations I have seen that use X-Ray-dependent inputs, they also use an hard-coded X-Ray propagator, disregarding any configured propagator, which is sensible.

This is not a per-trigger-type distinction, this is enumerating a set of pre-defined implementations of the EventToCarrier abstraction that can be selected at runtime.

I don't really get the difference, but what I meant is: There is no reason to make the user manually select "http" vs "sqs" when the event type can be automatically determined either from the function signature or by inspecting the payload JSON. Selecting them separately would only make sense if you have a function that receives both http and sqs events (not easily possible in statically typed languages like Java, .NET, but possible in priciple -- still probably unusual) and want to only extract context from one of them (I can't really come up with a reasonable use case for that)

I fully support not requiring the user to configure something that can be determined automatically. As such, separating sqs and http seems unnecessary.

specification/faas/aws-lambda.md

Aneurysm9 · 2023-07-06T15:23:16Z

specification/faas/aws-lambda.md


-[Span Link]: https://opentelemetry.io/docs/concepts/signals/traces/#span-links
+The `EventToCarrier` MUST implement the `Convert` operation to convert a lammbda `Event` into a `Carrier`.


I disagree. The linked .NET implementation does not appear to be user-provided and thus does not account for any event type not known to the instrumentation. It also does not provide a mechanism for extracting context information from any source other than the specific sources it has implemented. Because it combines the context propagation and event processing it does not provide any opportunity for composition to enable the user to establish a chain of responsibility. In fact, it's not at all implemented as an ordinary getter function that can be passed to a propagator, it is a sealed context extraction mechanism with limited knowledge of how to process a few event types.

Aneurysm9 · 2023-07-06T15:27:04Z

specification/faas/aws-lambda.md

+The `EventToCarrier` MUST implement the `Convert` operation to convert a lammbda `Event` into a `Carrier`.
+
+The `Convert` operation MUST have the following parameters:
+  `Carrier` - the carrier that will be populated from the `Event`


Why must the caller provide the carrier to populate? Should this not be a pure function of event -> carrier?

Aneurysm9 · 2023-07-06T15:32:53Z

specification/faas/aws-lambda.md

+
+Implementations MUST provide a facility to group multiple `EventToCarrier`s. A composite `EventToCarrier` can be built from a list of `EventToCarrier`s. The resulting composite `EventToCarrier` will invoke the `Convert` operation of each individual `EventToCarrier` in the order they were specified, sequentially updating the carrier.
+
+The list of `EventToCarrier`s passed to the composite `EventToCarrier` MUST be configured using the `OTEL_AWS_LAMBDA_EVENT_TO_CARRIERS`, as a comma separated list of values.


Why? New environment-based configuration cannot be added to the specification at this time.

At the very least this needs to be reduced to SHOULD, but I think it should be removed entirely.

Does OTEL_AWS_LAMBDA_EVENT_TO_CARRIERSenvironment variable also serve the purpose of exposing user-configurable event carrier ask from @Oberon00 comment above? https://github.com/open-telemetry/semantic-conventions/pull/164/files#r1254641850

If that is the case we should keep this as is or provide some configuration if not already provided (same ask in
@Oberon00in comment )

Aneurysm9 · 2023-07-06T15:36:13Z

specification/faas/aws-lambda.md

+
+The list of `EventToCarrier`s passed to the composite `EventToCarrier` MUST be configured using the `OTEL_AWS_LAMBDA_EVENT_TO_CARRIERS`, as a comma separated list of values.
+
+Valid values to configure the composite `EventToCarrier` are:


Suggested change

Valid values to configure the composite `EventToCarrier` are:

Valid values to configure the composite `EventToCarrier` include:

There may be reasons for other values to also be valid.

Aneurysm9 · 2023-07-06T15:40:00Z

specification/faas/aws-lambda.md

+
+Valid values to configure the composite `EventToCarrier` are:
+
+* `lambda_runtime` - populates the `Carrier` with a key `X-Amzn-Trace-Id` from the value of the `_X_AMZN_TRACE_ID` environment variable. (see note below)


This is not a per-trigger-type distinction, this is enumerating a set of pre-defined implementations of the EventToCarrier abstraction that can be selected at runtime.

As for the three toggles you propose, two and three are the same thing as long as a carrier can be extracted from the event and handed to the configured propagator. One is also effectively the same to the extent that an EventToCarrier implementation can always choose to include information in the carrier that was not in the incoming event but instead extracted from the operating environment or some other source.

The whole point of this is to separate the "Propagation using " from the second half of each of those sentences and to give the user the controls they need to choose what works best for them. We don't need to choose only three options for the user.

Aneurysm9 · 2023-07-06T15:42:35Z

specification/faas/aws-lambda.md

+* `http_headers` = populates the `Carrier` with the content of the http headers.
+* `sqs` - populate the carrier with the content of the `AWSTraceHeader` system attribute of the message.


Agreed, extracting a carrier from an SQS event should probably include both message attributes and message system attributes.

specification/faas/aws-lambda.md

Co-authored-by: Anthony Mirabella <[email protected]>

…lemetry#165)

…cs` (open-telemetry#166)

…nv (open-telemetry#171) Co-authored-by: Joao Grassi <[email protected]> Co-authored-by: Armin Ruech <[email protected]>

…-telemetry#170) Co-authored-by: Armin Ruech <[email protected]>

…eck (open-telemetry#177) Co-authored-by: Armin Ruech <[email protected]>

Signed-off-by: YANGDB <[email protected]> Co-authored-by: Josh Suereth <[email protected]>

…etry#175)

…y#180)

open-telemetry#187)

open-telemetry#190) Co-authored-by: Armin Ruech <[email protected]>

Co-authored-by: Josh Suereth <[email protected]>

…pen-telemetry#99) Co-authored-by: Pablo Baeyens <[email protected]> Co-authored-by: Tigran Najaryan <[email protected]> Co-authored-by: Dmitrii Anoshin <[email protected]> Co-authored-by: Armin Ruech <[email protected]>

…#224)

…#228)

…emetry#156) Co-authored-by: Armin Ruech <[email protected]>

…metry#241)

Signed-off-by: Raphael Silva <[email protected]>

* Clarify that users can provider their own EventToCarrier * Dont define the list of implementations * Remove the composite EventToCarrier

tylerbenson · 2023-08-14T15:36:10Z

docs/faas/aws-lambda.md

+
+Lambda instrumentation MUST provide a default `EventToCarrier`, the `HttpEventToCarrier`, which populates the `Carrier` with the content of the http headers used to invoke the lambda function.
+
+If no `EventToCarrier` is provided during the initialization of the lambda instrumentation, the `HttpEventToCarrier` MUST be used.


This doesn't take @Oberon00's feedback into account. As written, it seems that SQS lambda's will require explicit config to select the proper EventToCarrier implementation. This should not be required of users.

I see, is there anything in the proposal blocking the implementation of a EventToCarrier that is supposed to work with SQS? I don't think we need to list all possible cases and how they should be implemented, do we?

The important thing is that the lambda instrumentation can receive an EventToCarrier as parameter.

Listing cases that COULD be supported was a source of confusion in the previous revision of this proposal.

The problem is not missing cases, but that the user should not need to configure this explicitly. The implementation should automatically extract without the user configuring the trigger type explicitly.

jsuereth · 2023-10-23T17:07:38Z

Closing this in favor of ongoing discussion in #354.

Feat: Add EventToCarrier to AWS Lambda semantic conventions

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Signed-off-by: Raphael Silva <[email protected]>

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AWS X-Ray Environment Variable Propagation open-telemetry/opentelemetry-specification#3605

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feat(instrumentation-aws-lambda): Changed capturing of X-Ray context as span link open-telemetry/opentelemetry-js-contrib#1411

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* Clarify that users can provider their own EventToCarrier * Dont define the list of implementations * Remove the composite EventToCarrier

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FaaS: Change requirements regarding handling of AWS Lambda-provided SpanContext (take 2) #277

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Feat: Add EventToCarrier to AWS Lambda semantic conventions #164

Feat: Add EventToCarrier to AWS Lambda semantic conventions #164

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jsuereth commented Oct 23, 2023


		[Span Link]: https://opentelemetry.io/docs/concepts/signals/traces/#span-links
		The `EventToCarrier` MUST implement the `Convert` operation to convert a lammbda `Event` into a `Carrier`.

		* `http_headers` = populates the `Carrier` with the content of the http headers.
		* `sqs` - populate the carrier with the content of the `AWSTraceHeader` system attribute of the message.


		Valid values to configure the composite `EventToCarrier` are:

		* `lambda_runtime` - populates the `Carrier` with a key `X-Amzn-Trace-Id` from the value of the `_X_AMZN_TRACE_ID` environment variable. (see note below)


		Implementations MUST provide a facility to group multiple `EventToCarrier`s. A composite `EventToCarrier` can be built from a list of `EventToCarrier`s. The resulting composite `EventToCarrier` will invoke the `Convert` operation of each individual `EventToCarrier` in the order they were specified, sequentially updating the carrier.

		The list of `EventToCarrier`s passed to the composite `EventToCarrier` MUST be configured using the `OTEL_AWS_LAMBDA_EVENT_TO_CARRIERS`, as a comma separated list of values.


		Lambda instrumentation MUST provide a default `EventToCarrier`, the `HttpEventToCarrier`, which populates the `Carrier` with the content of the http headers used to invoke the lambda function.

		If no `EventToCarrier` is provided during the initialization of the lambda instrumentation, the `HttpEventToCarrier` MUST be used.

Feat: Add EventToCarrier to AWS Lambda semantic conventions #164

Feat: Add EventToCarrier to AWS Lambda semantic conventions #164

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