Accelerate export of language container

[tomuben]

Background

when running exaslct export we run basically the following steps:

• build the docker images of respective flavor (if not existent)
• create docker container (but not start)
• export (whole) docker container to tar
• zip the tar, excluding certain directories

For huge containers the last two steps might become a pain point, for a 5GB container we measured ~15 minutes.

It should be possible to increase the speed of the export by starting the container and then exporting directories from inside the container, also using a compression tool which leverage multiple CPU cores (pigz).

Acceptance Criteria

• Install pigz on all containers
• Modify export_container_base_task so that it:
  • Starts the container, mounting a temporary directory
  • Creates the tar.gz from inside of the container to the mounted directory, ignoring the given list of directories