Update AWS Lambda SDK to 1.28.0

[ohookins]

I've been scratching my head the last few days about this. The daemon itself works standalone, and will even do so packaged as a Docker image and used with lambda, but will run immediately and exit - not suitable for lambda usage. If you build the lambda subdirectory directly and produce a binary (presumably what is provided as handler.zip in release) it seems to work when packaged as a zip file but not when packaged as a Docker image.

I couldn't seem to determine what was causing problems but it's clearly:

• the current codebase
• when packaged as a Docker image and used as an AWS lambda function
• the binary itself and the code (e.g. main()) is executed, but the Handler function is never called by the AWS lambda runtime.

After trying a few different things, it seems like updating to a later version of the AWS Lambda SDK solves the issue. I suspect some subtle interoperation between the runtime and the specific version of this SDK is not working - after all, it's almost 4 years old at this point.

[ohookins]

For reference, this is how I'm building the Docker image:

FROM public.ecr.aws/lambda/provided:al2 as build

# See https://github.com/buildkite/buildkite-agent-metrics/releases for latest version
ENV LAMBDA_VERSION="5.3.0"

WORKDIR /app
COPY . /app

RUN yum install -y wget tar golang && \
    wget "https://github.com/buildkite/buildkite-agent-metrics/archive/refs/tags/v${LAMBDA_VERSION}.tar.gz" && \
    tar xvzf "v${LAMBDA_VERSION}.tar.gz" && \
    cd "buildkite-agent-metrics-${LAMBDA_VERSION}" && \
    go get ./lambda && \
    CGO_ENABLED=0 go build -o ../handler ./lambda

FROM public.ecr.aws/lambda/provided:al2

COPY --from=build /app/handler ${LAMBDA_TASK_ROOT}

ENTRYPOINT ["./handler"]

[moskyb]

hi there @ohookins! thanks for contributing.

this looks awesome! great work on the bug hunt - i suspect that the previous version of the lambda-go package we were using predates container lambdas, which i imagine is why it doesn't play nicely with them 😅

i'm happy to merge this as-is, but it seems like the dockerfile you've posted above might be useful to people as well - would you be interested in adding it as lambda.Dockerfile (or something) as part of this PR?

[ohookins]

Yeah, I can add that no problem. I tend to use things like Dockerfile.test so perhaps Dockerfile.lambda ?

Actually there is a small problem with it I realise, AWS's provided:al2 ships with Golang 1.15 so in my local environment I've been using golang:1.17 as the build image, and the go.mod specifies 1.16 minimum version. I'll just retest the instructions and then add it to the branch if that still sounds ok.

[ohookins]

@moskyb anything else you need from me on this? How does that Dockerfile look? What's the release process from here?

[moskyb]

i have a couple of comments on the dockerfile, but i'm also happy to merge this as is and make the changes myself - i'm aware of how annoying it might be for someone from some other company to say "yeah include that other thing, that looks great!" and then pick it to pieces at the next turn 😅

[moskyb]

re: the release process, once i have your okay, i'll merge it and make a release against this repo, which will publish the new versions of the handlers, binaries etc.

[ohookins]

You are free to merge it at any time! Up to you whether the LAMBDA_VERSION is a blocker or a nit.

[ohookins]

OK should be good to go now.

[moskyb]

Awesome! Thanks so much for your contribution @ohookins, i'm really happy with where we got to :)