AWS Lambda Instrumentation

[rasviitanen]

We ran into some issues running tracing-honeycomb on AWS lambda.

Basically we experienced two problems:

1. Lambda functions resolves once it replies to the requestee, so libhoney would need flush its queued events before a response can be sent. This can take a while and lead to poor performance, as flushing libhoney is not instant.
2. libhoney does not handle flushing of queued events very well (Queued events are ignored when flushing client nlopes/libhoney-rust#65).

Luckily, Honeycomb provides a layer that fixes this: https://docs.honeycomb.io/getting-data-in/integrations/aws/aws-lambda/

To make it work with tracing-honeycomb, it would need to send its spans to stdout instead of a libhoney client.

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We have been working on a fix that makes the HoneycombTelemetry generic over some Reporter, where you can pick either Stdout/Libhoney via a builder.

Is this something you would like to see added to this repository?
We would be happy to add our implementation if so.

[Fishrock123]

Yes please. We'd like to run rust lambdas in the near future as well and this would be very much appreciated!

[Fishrock123]

Released in 0.4.1: https://github.com/eaze/tracing-honeycomb/releases/tag/tracing-honeycomb-0.4.1

(I yanked 0.4.0 due to the wrong git commit)