AWS Build Project succeeds even when a command fails in buildspec.yml - amazon-web-services

Question

I'm using AWS CodeBuild to deploy the function to AWS lambda using serverless-framework.
Here is my buildspec.yml,
version: 0.2
phases:
install:
runtime-versions:
nodejs: 10
commands:
- echo installing Mocha...
- npm install -g mocha
- echo installing Serverless...
- npm install -g serverless
pre_build:
commands:
- echo running npm install for global project...
- npm install
- echo running npm install for each function...
- folders=src/*
- for value in $folders;
do
echo $value
npm --prefix $value install $value;
done
build:
commands:
- sls package
- serverless deploy --stage $STAGE --region $AWS_DEFAULT_REGION | tee deploy.out
post_build:
commands:
- echo done
# - . ./test.sh
The problem is even when the serverless deploy --stage $STAGE --region $AWS_DEFAULT_REGION | tee deploy.out command fails, the build project is shown as success by AWS codebuild in the codepipeline.
I want the build status as failure when serverless deploy command fails.

Answer 1

This happens because post_build executes whether build fails or succeeds. Thus it does not meter that build fails, post_build will run anyway. This is explained in the build phase transitions.
You can rectify this by "manually" checking if build failed in post_build by checking CODEBUILD_BUILD_SUCCEEDING env variable:
CODEBUILD_BUILD_SUCCEEDING: Whether the current build is succeeding. Set to 0 if the build is failing, or 1 if the build is succeeding.
Thus in your post_build you can check ifCODEBUILD_BUILD_SUCCEEDING == 0 and exit 1 if is true.
post_build:
commands:
- if [[ $CODEBUILD_BUILD_SUCCEEDING == 0 ]]; then exit 1; fi
- echo done
# - . ./test.sh

Answer 2

Your command:
- serverless deploy --stage $STAGE --region $AWS_DEFAULT_REGION | tee deploy.out
... is not returning a non-zero code on failure which is required to fail the build. The command tee is masking the return code from serverless deploy as it itself is responding with a '0' return code.
I would recommend to re-write the command as:
- serverless deploy --stage $STAGE --region $AWS_DEFAULT_REGION > deploy.out
- cat deploy.out