composer install fails when unable to see mysql database

Question

TL;DR: composer install fails when the post-install scripts can't see a MySQL server

I'm building a docker container for a Symfony application, and during the build I do something like this

RUN export SYMFONY_ENV=prod && \
  composer install --prefer-dist --optimize-autoloader

Towards the end of the install, it fails with this

Generating optimized autoload files


  [Doctrine\DBAL\Exception\DriverException]                                                                  
  An exception occured in driver: SQLSTATE[HY000] [2003] Can't connect to MySQL server on '127.0.0.1' (111)  

  [Doctrine\DBAL\Driver\PDOException]                                        
  SQLSTATE[HY000] [2003] Can't connect to MySQL server on '127.0.0.1' (111)  

  [PDOException]                                                             
  SQLSTATE[HY000] [2003] Can't connect to MySQL server on '127.0.0.1' (111)  


Script Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::clearCache handling the post-install-cmd event terminated with an exception

  [RuntimeException]                                                         
  An error occurred when executing the "'cache:clear --no-warmup'" command.  

Now, I could use --no-scripts but then presumably I'd need to run composer install again after starting a container, and I'd like my container to be as ready as possible.

As I've not found many references to similar problems, there might be something in my application at fault, and I suspect I'll be answering my own question. My hope was that in describing it, I would figure it out. Alas, I haven't. Clues are welcome :)

Answer 1

Doctrine introduced some code which tried to auto-detect things about the database quite eagerly.

A workaround is simply to tell Doctrine the target server version, e.g.

doctrine:
    dbal:
        default_connection: default
        connections:
            default:
                dbname:   Symfony2
                user:         root
                password: null
                host:         localhost
                driver:       pdo_mysql
                server_version: 5.6

See https://github.com/doctrine/DoctrineBundle/issues/351#issuecomment-75456547