Composer Error in Jenkins - php

Question

I have been trying to setup a build system for PHP and has the following Jenkins pipeline.
pipeline {
agent { docker { image 'my-custom-image' } }
stages {
stage('Build') {
steps {
sh 'composer config --global --auth http-basic.repo.packagist.com token mytokencode'
}
}
}
}
Here it is pulling the docker image, but when the composer command is executed, it it throwing following error :
Cannot create cache directory /.composer/cache/repo/https---repo.packagist.com-domain/, or directory is not writable. Proceeding without cache
Cannot create cache directory /.composer/cache/files/, or directory is not writable. Proceeding without cache
[ErrorException]
touch(): Unable to create file /.composer/config.json because No such file or directory
and the build is failing. How can I fix this ?

Answer 1

You could set the COMPOSER_HOME environment variable to the actual directory, them Composer will save all the cache data there. Something like:
pipeline {
agent { docker { image 'my-custom-image' } }
stages {
stage('Build') {
steps {
sh 'COMPOSER_HOME=$(pwd) composer config --global --auth http-basic.repo.packagist.com token mytokencode'
}
}
}
}

Answer 2

I was able to use composer cache by creating a volume between my Jenkins machine and the Docker image. You can try to reproduce:
At your pipeline script, create the volume using an argument:
agent {
docker {
image 'my-custom-image'
args '-v $HOME/.composer/cache:/usr/local/share/composer/cache'
}
}
Check where your $HOME directory is pointing to, it can be different depending on how you installed Jenkins. I'm using it as an apt package on Ubuntu 16. For me, it's pointing to /var/lib/jenkins
Inside your $HOME directory, a folder named ".composer" is needed with right permissions so the docker can use it. I set it up with chmod -R 775.