GLIBC not found with AWS SAM and Golang

A small AWS SAM project stopped working due to my OS updating to a newer dependency version that SAM couldn’t use.

The error I’d run into occurred when running the Lambda function:

/var/task/healthcheck: /lib64/libc.so.6: version `GLIBC_2.32' not found (required by /var/task/healthcheck)
/var/task/healthcheck: /lib64/libc.so.6: version `GLIBC_2.34' not found (required by /var/task/healthcheck)
2022/10/01 18:48:58 exit status 1
01 Oct 2022 18:48:58,162 [ERROR] (rapid) Init failed error=Runtime exited with error: exit status 1 InvokeID=
/var/task/healthcheck: /lib64/libc.so.6: version `GLIBC_2.32' not found (required by /var/task/healthcheck)
/var/task/healthcheck: /lib64/libc.so.6: version `GLIBC_2.34' not found (required by /var/task/healthcheck)
2022/10/01 18:48:58 exit status 1

This error has been reported to aws-lambda-go here, however, the fix is to build the project using go build, and I’ve been using sam build.

I did try using sam build --use-containers, which I assume would have all the dependencies needed by AWS, but that doesn’t work for Golang projects.

Since go build can build binaries that will work with AWS Lambda, it makes sense to try and use that instead of the build created by sam build.

@shearn89 describes how this can be done by configuring a BuildMethod.

By setting the BuildMethod to makefile, the sam CLI will copy the functions files into a temp directory, run a make target and expect a binary to be built into the $ARTIFACTS_DIR directory.

The Solution

For context, my project is structured like so:

.
├── go.mod
├── go.sum
├── Makefile
├── samconfig.toml
├── template.yaml
├── lambda
│   ├── healthcheck
│   │   ├── healthcheck.go ✨
│   │   └── healthcheck_test.go
│   └── <function group>
│       └── <function group>
│           ├── <function>.go ✨
│           └── <function>_test.go
└── utils
    └── jsonresponse
        ├── jsonresponse.go
        └── jsonresponse_test.go

The lambda/ directory contains the functions that will run on AWS Lambda. The go.mod file is at the root of the project allowing my Lambda functions to reference local packages like utils/jsonresponse/jsonresponse.go.

Add ‘BuildMethod: makefile’ to your template

Change your template file to use a makefile instead of sam’s build method.

Initially my template looked like this:

HealthCheckFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: lambda/healthcheck/
      Handler: healthcheck
      FunctionName: !Sub "healthcheck_${Env}"
      Runtime: go1.x
      Architectures:
        - x86_64
      Events:
        ...

To build with a Makefile, we need to add a Metadata > BuildMethod attribute to the function definition and I had to change the CodeUri path so that sam build will copy the whole code base into its temp directory and go build can use the root directories go.mod file.

With these changes, the function definition becomes:

HealthCheckFunction:
    Type: AWS::Serverless::Function
    Metadata:
      BuildMethod: makefile
    Properties:
      CodeUri: .
      Handler: healthcheck
      FunctionName: !Sub "healthcheck_${Env}"
      Runtime: go1.x
      Architectures:
        - x86_64
      Events:
        ...

Add a Makefile

You’ll need to create a Makefile in the same directory as the CodeUri for each of your functions.

I already had a Makefile, so I started by adding the following target:

build-HealthCheckFunction:
  GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -o healthcheck lambda/healthcheck/healthcheck.go
  mv healthcheck $(ARTIFACTS_DIR)

The target has the name build-<Template Function Name> and the binaries are placed in the $ARTIFACTS_DIR so sam can access them.

Cleanup make file

Once I got this working, I moved the Lambda function methods into a separate file lambda.mk, which I pull into my make file:

include lambda.mk

Then I re-jigged the build-* targets like so:

build-lambda-function:
  ls -l
  GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -o $(HANDLER) lambda/$(DIR)/$(HANDLER).go
  mv $(HANDLER) $(ARTIFACTS_DIR)/

build-HealthCheckFunction: HANDLER=healthcheck
build-HealthCheckFunction: DIR=healthcheck
build-HealthCheckFunction: build-lambda-function

build-.....

With these changes, I can run sam build or sam local start-api as normal and no more errors.