Error loading shared library libresolv.so.2 in Python Alpine Docker-CodePudding

I am using Alpine Linux as Docker image for my Python app in CI/CD (Jenkins). This is for AWS Lambda, basically the only noteworthy requirement is aws-psycopg2 for accessing Postgres. Locally everything works, it deploys nicely with Serverless and works on AWS, the only problem is on Jenkins. I am getting an error there:

16:24:55  ImportError: Error loading shared library libresolv.so.2: No such file or directory (needed by /usr/local/lib/python3.9/site-packages/psycopg2/../psycopg2_binary.libs/libgssapi_krb5-497db0c6.so.2.2)

I am NOT using Oracle in any way, like e.g. in this question.

My jenkinsfile.groovy:

def testInstallStage = {
  stage('Install') {
    sh 'apk add python3-dev gcc libc-dev musl-dev openblas gfortran build-base postgresql-libs postgresql-dev libffi-dev cargo'
    sh 'pip install --upgrade pip && pip install poetry'
    sh 'poetry export --without-hashes --dev -f requirements.txt -o requirements.txt --with-credentials'
    sh 'pip install -r requirements.txt'

    sh 'pip install awscli'
    sh 'aws configure set aws_access_key_id default_access_key'
    sh 'aws configure set aws_secret_access_key default_secret_key'
    sh 'aws configure set default.region eu-west-1'

    sh 'cp config/jenkins.json config.json'
  }
}

def testStage = {
  stage('Tests') {
    sh 'pip install nose && nosetests'
  }
}

new pl.ruby.PipelineRunner(this, notificationChannel).run() {
  pythonStack([image: '3.9.13-alpine3.16'], {
    container('python') {
      testInstallStage.call()
      testStage.call()
    }
  })
}

The whole line with apk add is from me trying to fix this. I tried installing many different dependencies. What should I install to get this working? I know that this is some library missing on Alpine, since on Ubuntu 20.04 and on AWS Lambda runtime it works ok.

CodePudding user response：

The library libresolv.so.2 is part of the system C library. Alpine-based images use a different version of the C library (musl libc) which is much smaller, but also occasionally runs into compatibility issues like this.

The easiest way around this is to switch to a Debian- or Ubuntu-based image based on the more standard GNU libc. Since you're using an unmodified image here you'd just need to remove the "Alpine" reference in the image tag

pythonStack([image: '3.9.13'], ...)

In a custom Dockerfile you might also need to change the package manager invocations if you need to install any OS-level packages, since Debian/Ubuntu and Alpine have different packaging formats, tools, and names. The first line of your testInstallStage would also be affected by this.

The typical reason to use an Alpine-based image is to save space. The actual space savings here are fairly small (tens of megabytes) and once you start installing C header files the images quickly get much larger than this. You're probably not going to notice a practical difference in performance or image size making this change.