aws/aws-cdk

(core): Docker stdout is not printed on error during bundling

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#20892 opened on Jun 28, 2022

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Description

Describe the bug

In quite a few different scenarios, Docker errors simply happen and "Docker returned 1" gets spat out.

I suspect Docker is writing to stderr but it is getting squashed somewhere.

Expected Behavior

Docker outputs (both stdout and stderr are preserved)

Current Behavior

Docker's error status isn't printed

Reproduction Steps

  • Run cdk synth on a stack that requires docker, but without permissions to talk to Docker's control plane
  • watch as it crashes and burns:
39907defbe84: Pull complete
8f7631647f07: Pull complete
d83e11d24ec9: Pull complete
b09b92bf5cf8: Pull complete
[WARNING] 
software.amazon.jsii.JsiiException: docker exited with status 1
Error: docker exited with status 1
    at dockerExec (/tmp/jsii-kernel-ENBrAx/node_modules/@aws-cdk/core/lib/bundling.js:355:15)
    at Function.fromBuild (/tmp/jsii-kernel-ENBrAx/node_modules/@aws-cdk/core/lib/bundling.js:243:9)
    at new Bundling (/tmp/jsii-kernel-ENBrAx/node_modules/@aws-cdk/aws-lambda-python/lib/bundling.js:28:86)
    at Function.bundle (/tmp/jsii-kernel-ENBrAx/node_modules/@aws-cdk/aws-lambda-python/lib/bundling.js:43:50)
    at new PythonFunction (/tmp/jsii-kernel-ENBrAx/node_modules/@aws-cdk/aws-lambda-python/lib/function.js:43:39)

The error that is being quashed here was Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post "http://%2Fvar%2Frun%2Fdocker.sock/v1.24/images/create?fromImage=public.ecr.aws%2Fsam%2Fbuild-python3.7&tag=latest": dial unix /var/run/docker.sock: connect: permission denied

Contributor guide

Tech stack
typescriptnodejsdocker
Domain
clouddevops
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Familiarity with Node.js child processBasic Docker knowledge
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
The bug is in the Docker output handling in AWS CDK core. Look at file `packages/@aws cdk/core/lib/bundling.js`, specifically the `dockerExec` function. The issue is that stderr from Docker is not printed on error; only 'docker exited with status 1' is shown. The fix likely involves modifying how child process.execSync or similar captures output. Check comments on the issue for any proposed solutions or maintainer guidance.