Minimize usage of disk space during export

[tomuben]

Background

The export API uses currently five times the space of the SLC (see here):

1. The docker image
2. The TAR file
3. The unextracted TAR file (Directory)
4. The packed modified TAR file
5. The compressed modified TAR file

We can delete the TAR file/Directory in step 2 and step 3 after they are not needed.
Also we could provide an additional command line parameter to delete the docker image when it's not needed anymore.

[tkilias]

Clean up of docker images, requires to call the clean images task, that means ExportContainerBaseTask needs to idempotent. That means we need to extract expensive operations into their own task.

Functions that need their own Task:

1. Function needs to get a task

• script-languages-container-tool/exasol/slc/internal/tasks/export/export_container_base_task.py

  Line 65 in 7757e2f

  self._remove_cached_exported_file_if_requested(cache_file, checksum_file)

2. Block needs to be a task

• script-languages-container-tool/exasol/slc/internal/tasks/export/export_container_base_task.py

  Line 67 in 7757e2f

  is_new = False

• script-languages-container-tool/exasol/slc/internal/tasks/export/export_container_base_task.py

  Line 73 in 7757e2f

  )

3. Function needs to be a task

• script-languages-container-tool/exasol/slc/internal/tasks/export/export_container_base_task.py

  Line 146 in 7757e2f

  def _export_release(

4. Function needs to be a task

• script-languages-container-tool/exasol/slc/internal/tasks/export/export_container_base_task.py

  Line 155 in 7757e2f

  export_file = self._create_and_export_container(