Aws-sam-cli: Sam local start-api fetches image and mounts source on every request

[csears]

Hi There,

I'm using sam 0.5.0 on macOS and testing the start-api hot reloading with a nodejs 8.10 project.

On the first request, sam downloaded the lambci/lambda:nodejs8.10 and mounted my source directory as expected. At this point, I would not expect sam to fetch the Docker image again and only re-mount the source directory if something in my code changed.

Instead, it tries to fetch the Docker image and remounts my source directory with every request:

Fetching lambci/lambda:nodejs8.10 Docker container image......
2018-08-08 13:45:33 Mounting /source/code as /var/task:ro inside runtime container

I assume this is not the expected behavior.

[jfuss]

This is expected behavior. If you already have the container locally (in your case the nodejs8.10), then you can use --skip-pull-image to remove the download.

We have some converstations here about changing this behavior (#529).

Here is the code where this happens.

Closing since it is expected behavior and already have other issues discussing ways we can improve this.

[alvaropaco]

May be considerate to have an option to skip the image build.