Create Lambda Layer in Dockerfile

Question

Hi, just wondering, during docker build, if I install node packages in the folder `/opt/nodejs` and copy the folder `node_modules/` plus files `package.*` to the final image like the following:
```
FROM public.ecr.aws/lambda/nodejs:16 as builder
WORKDIR /opt/nodejs
RUN npm install pkg1 pkg2 pkg3

FROM public.ecr.aws/lambda/nodejs:16
COPY --from=builder /opt/nodejs /opt/nodejs
COPY . ${LAMBDA_TASK_ROOT}
```
would this be a valid way to create a lambda layer? Thanks!

Accepted Answer

Lambda container images does not support layers. Layers are only a way to add dependencies, so all you have to do is include those dependencies in your docker image. Layers use the /opt. When you use docker, you don't have to use /opt and you can deploy your dependencies in the regular location.

I don't think you need to use FROM twice. Just use the second, npm install, and copy the application files.

Answer

I don't know in JS, but in Python what I would do is use the docker image provided by lambda to install my packages into a specific folder. Zip that, store it in S3, job done. So yes, I suppose a multi-stages build works as well. But again, I am not familiar with the specific inner workings of NPM to achieve that.

Create Lambda Layer in Dockerfile

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