For some reason my docker file with lein uberjar in it gives the following error on a push

Enumerating objects: 1986, done.
Counting objects: 100% (1984/1984), done.
Delta compression using up to 16 threads
Compressing objects: 100% (1901/1901), done.
Writing objects: 100% (1942/1942), 28.23 MiB | 1.87 MiB/s, done.
Total 1942 (delta 646), reused 0 (delta 0)
remote: Compressing source files... done.        
remote: Building source:        
remote: === Fetching app code
remote: 
remote: === Building web (Dockerfile)        
remote: 
remote: =!= Dockerfile parse error line 40: unknown instruction: LEIN        
remote: Verifying deploy...
remote: 
remote: !	Push rejected to vendomarch.        
remote: 
To 
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to ''

why?

I’d guess the lein tool isn’t available in your Docker build environment, reason for that is entirely dependent on your project setup though. There’s a longer argument to be had (and it’d be an argument, not really a discussion) about the pros and cons of building inside Docker itself which, again, is dependent on your project setup. So with this information it’s quite hard to say anything conclusive 🙂