Add a new register-task-types cli that will create missing task-type entries in the
scheduler according to:
- only create missing task-types (do not update them), but check that the
backend_name field is consistent,
- each SWHTask-based task declared in a module listed in the 'task_modules'
plugin registry field will be checked and added if needed; tasks which name
start wit an underscore will not be added,
- added task-type will have:
- the 'type' field is derived from the task's function name (with underscores
replaced with dashes),
- the description field is the first line of that function's docstring,
- default values as provided by the swh.lister.cli.DEFAULT_TASK_TYPE (with
a simple pattern matching to have decent default values for full/incremental
tasks),
- these default values can be overloaded via the 'task_type' plugin registry
entry.
For this, we had to rename all tasks names (eg. `cran_lister` -> `list_cran`).
Comes with some tests.
Listers are declared as plugins via the `swh.workers` entry_point.
As such, the registry function is expected to return a dict with the
`task_modules` field (as for generic worker plugins), plus:
- `lister`: the lister class,
- `models`: list of SQLAlchemy models used by this lister,
- `init` (optionnal): hook (callable) used to initialize the lister's state
(typically, create/initialize the database for this lister).
If not set, the default implementation creates database tables (after
optionally having deleted exisintg ones) according to models declared in
the `models` register field.
There is no need for explicitely add lister task modules in the main
`conftest` module, but any new/extra lister to be tested must be registered
(the tested lister module must be properly installed in the test environment).
Also refactor a bit the cli tools:
- add support for the standard --config-file option at the 'lister' group
level,
- move the --db-url to the 'lister' group,
- drop the --lister option for the `swh lister db-init` cli tool:
initializing (especially with --drop-tables) the database for a single
lister is unreliable, since all tables are created using a sibgle MetaData
(in the same namespace).
Get rid of the class based task definition in favor of decorator-based
task declarations.
Doing so, we can get rid of core/tasks.py
Task names are explicitely set to keep compatibility with task
definitions in schedulers' database.
This also add debug statements at the beginning and end of each lister
task.
