Пример #1
0
def main():
    # TODO: Test both with and without a provided config file.
    kwargs = {}
    if len(sys.argv) > 1:
        cfg = ru.Config(cfg=ru.read_json(sys.argv[1]))
        kwargs['cfg'] = cfg
        descr = cfg.worker_descr,
        count = cfg.n_workers,
        cores = cfg.cpn,
        gpus = cfg.gpn
    else:
        descr = rp.TaskDescription({
            'uid': 'raptor.worker',
            'executable': 'scalems_rp_worker',
            'arguments': []
        })
        count = 1
        cores = 1
        gpus = 0
    master = ScaleMSMaster(**kwargs)

    master.submit(descr=descr, count=count, cores=cores, gpus=gpus)

    master.start()
    master.join()
    master.stop()
Пример #2
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def test_rp_basic_task_remote(rp_task_manager, pilot_description):
    import radical.pilot as rp

    if pilot_description.access_schema and pilot_description.access_schema == 'local':
        pytest.skip('This test is only for remote execution.')

    tmgr = rp_task_manager
    session = tmgr.session
    assert not session.closed

    td = rp.TaskDescription({
        'executable': '/usr/bin/hostname',
        'cpu_processes': 1
    })

    task = tmgr.submit_tasks(td)

    tmgr.wait_tasks(uids=[task.uid])

    assert task.state == rp.states.DONE
    assert task.exit_code == 0

    localname = subprocess.run(['/usr/bin/hostname'],
                               stdout=subprocess.PIPE,
                               encoding='utf-8').stdout.rstrip()
    remotename = task.stdout.rstrip()
    assert len(remotename) > 0
    assert remotename != localname
Пример #3
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def _describe_raptor_task(item: scalems.workflow.Task, scheduler: str,
                          pre_exec: list) -> rp.TaskDescription:
    """Derive a RADICAL Pilot TaskDescription from a scalems workflow item.

    The TaskDescription will be submitted to the named *scheduler*,
    where *scheduler* is the UID of a task managing the life of a rp.raptor.Master
    instance.

    Caller is responsible for ensuring that *scheduler* is valid.
    """
    # Warning: TaskDescription class does not have a strongly defined interface.
    # Check docs for schema.
    # Ref: scalems_rp_master._RaptorTaskDescription
    task_description = rp.TaskDescription(from_dict=dict(
        executable=
        'scalems',  # This value is currently ignored, but must be set.
        pre_exec=pre_exec))
    task_description.uid = item.uid()
    task_description.scheduler = str(scheduler)
    # Example work would be the JSON serialized form of the following dictionary.
    # {'mode': 'call',
    #  'cores': 1,
    #  'timeout': 10,
    #  'data': {'method': 'hello',
    #           'kwargs': {'world': uid}}}
    #
    # Maybe something like this:
    # work_dict = {
    #     'mode': 'scalems',
    #     'cores': 1,
    #     'timeout': 10,
    #     'data': item.serialize()
    # }
    work_dict = {
        'mode': 'exec',
        'cores': 1,
        'timeout': None,
        'data': {
            'exe': item.input['argv'][0],
            'args': item.input['argv'][1:]
        }
    }
    task_description.arguments = [json.dumps(work_dict)]

    # TODO: Check for and activate an appropriate venv
    # using
    #     task_description.pre_exec = ...
    # or
    #     task_description.named_env = ...

    # TODO: Interpret item details and derive appropriate staging directives.
    task_description.input_staging = []
    task_description.output_staging = []

    return task_description
Пример #4
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def _describe_legacy_task(item: scalems.workflow.Task,
                          pre_exec: list) -> rp.TaskDescription:
    """Derive a RADICAL Pilot TaskDescription from a scalems workflow item.

    For a "raptor" style task, see _describe_raptor_task()
    """
    subprocess_type = TypeIdentifier(
        ('scalems', 'subprocess', 'SubprocessTask'))
    assert item.description().type() == subprocess_type
    input_data = item.input
    task_input = scalems.subprocess.SubprocessInput(**input_data)
    args = list([arg for arg in task_input.argv])
    # Warning: TaskDescription class does not have a strongly defined interface.
    # Check docs for schema.
    task_description = rp.TaskDescription(
        from_dict=dict(executable=args[0],
                       arguments=args[1:],
                       stdout=str(task_input.stdout),
                       stderr=str(task_input.stderr),
                       pre_exec=pre_exec))
    uid: str = item.uid().hex()
    task_description.uid = uid

    # TODO: Check for and activate an appropriate venv
    # using
    #     task_description.pre_exec = ...
    # or
    #     task_description.named_env = ...

    # TODO: Interpret item details and derive appropriate staging directives.
    task_description.input_staging = list(task_input.inputs.values())
    task_description.output_staging = [{
        'source':
        str(task_input.stdout),
        'target':
        os.path.join(uid,
                     pathlib.Path(task_input.stdout).name),
        'action':
        rp.TRANSFER
    }, {
        'source':
        str(task_input.stderr),
        'target':
        os.path.join(uid,
                     pathlib.Path(task_input.stderr).name),
        'action':
        rp.TRANSFER
    }]
    task_description.output_staging += task_input.outputs.values()

    return task_description
Пример #5
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def _get_scheduler(name: str, pre_exec: typing.Iterable[str],
                   task_manager: rp.TaskManager):
    """Establish the radical.pilot.raptor.Master task.

    Create a master rp.Task (running the scalems_rp_master script) with the
    provide *name* to be referenced as the *scheduler* for raptor tasks.

    Returns the rp.Task for the master script once the Master is ready to
    receive submissions.

    Raises:
        DispatchError if the master task could not be launched successfully.

    Note:
        Currently there is no completion condition for the master script.
        Caller is responsible for canceling the Task returned by this function.
    """
    # This is the name that should be resolvable in an active venv for the script we
    # install as
    # pkg_resources.get_entry_info('scalems', 'console_scripts', 'scalems_rp_master').name
    master_script = 'scalems_rp_master'

    # We can probably make the config file a permanent part of the local metadata,
    # but we don't really have a scheme for managing local metadata right now.
    # with tempfile.TemporaryDirectory() as dir:
    #     config_file_name = 'raptor_scheduler_config.json'
    #     config_file_path = os.path.join(dir, config_file_name)
    #     with open(config_file_path, 'w') as fh:
    #         encoded = scalems_rp_master.encode_as_dict(scheduler_config)
    #         json.dump(encoded, fh, indent=2)

    # define a raptor.scalems master and launch it within the pilot
    td = rp.TaskDescription({'uid': name, 'executable': master_script})
    td.arguments = []
    td.pre_exec = pre_exec
    # td.named_env = 'scalems_env'
    logger.debug('Launching RP scheduler.')
    scheduler = task_manager.submit_tasks(td)
    # WARNING: rp.Task.wait() *state* parameter does not handle tuples, but does not
    # check type.
    scheduler.wait(state=[rp.states.AGENT_EXECUTING] + rp.FINAL)
    if scheduler.state not in {rp.states.CANCELED, rp.states.FAILED}:
        raise DispatchError('Could not get Master task for dispatching.')
    return scheduler
Пример #6
0
    def _job_2_descr(self, job):

        # FIXME: RP does not support STDIN.  Should we raise if STDIN is
        #        specified?

        from_dict = dict()

        # TODO: use meta data for jpsi uid
        from_dict['name'] = job.uid

        from_dict['executable'] = job.spec.executable
        from_dict['arguments'] = job.spec.arguments
        from_dict['environment'] = job.spec.environment
        # from_dict['stdin'      ] = job.spec.stdin_path
        from_dict['stdout'] = job.spec.stdout_path
        from_dict['stderr'] = job.spec.stderr_path
        from_dict['sandbox'] = job.spec.directory

        return rp.TaskDescription(from_dict=from_dict)
Пример #7
0
def test_prepare_venv(rp_task_manager, sdist):
    """Bootstrap the scalems package in a RP target environment using pilot.prepare_env.

    This test function specifically tests the local.localhost resource.

    Note that we cannot wait on the environment preparation directly, but we can define
    a task with ``named_env`` matching the *prepare_env* key to implicitly depend on
    successful creation.
    """
    # NOTE: *sdist* is a path of an sdist archive that we could stage for the venv installation.
    # QUESTION: Can't we use the radical.pilot package archive that was already placed for bootstrapping the pilot?

    # TODO: Merge with test_rp_raptor_local but use the installed scalems_rp_master and scalems_rp_worker files

    import radical.pilot as rp
    import radical.saga as rs
    import radical.utils as ru
    # We only expect one pilot
    pilot: rp.Pilot = rp_task_manager.get_pilots()[0]
    # We get a dictionary...
    # assert isinstance(pilot, rp.Pilot)
    # But it looks like it has the pilot id in it.
    pilot_uid = typing.cast(dict, pilot)['uid']
    pmgr_uid = typing.cast(dict, pilot)['pmgr']
    session: rp.Session = rp_task_manager.session
    pmgr: rp.PilotManager = session.get_pilot_managers(pmgr_uids=pmgr_uid)
    assert isinstance(pmgr, rp.PilotManager)
    pilot = pmgr.get_pilots(uids=pilot_uid)
    assert isinstance(pilot, rp.Pilot)
    # It looks like either the pytest fixture should deliver something other than the TaskManager,
    # or the prepare_venv part should be moved to a separate function, such as in conftest...

    sdist_names = {
        'scalems': os.path.basename(sdist),
        'rp': rp.sdist_name,
        'ru': ru.sdist_name,
        'rs': rs.sdist_name
    }
    sdist_local_paths = {
        'scalems': sdist,
        'rp': rp.sdist_path,
        'rs': rs.sdist_path,
        'ru': ru.sdist_path
    }
    logger.debug('Checking paths: ' + ', '.join(sdist_local_paths.values()))
    for path in sdist_local_paths.values():
        assert os.path.exists(path)

    sandbox_path = urllib.parse.urlparse(pilot.pilot_sandbox).path

    sdist_session_paths = {
        name: os.path.join(sandbox_path, sdist_names[name])
        for name in sdist_names.keys()
    }

    logger.debug('Staging ' + ', '.join(sdist_session_paths.values()))

    input_staging = []
    for name in sdist_names.keys():
        input_staging.append({
            'source': sdist_local_paths[name],
            'target': sdist_session_paths[name],
            'action': rp.TRANSFER
        })
    pilot.stage_in(input_staging)

    tmgr = rp_task_manager

    pilot.prepare_env({
        'scalems_env': {
            'type': 'virtualenv',
            'version': '3.8',
            'setup': list(sdist_session_paths.values())
        }
    })

    td = rp.TaskDescription({
        'executable':
        'python3',
        'arguments': [
            '-c', 'import radical.pilot as rp;'
            'import scalems;'
            'print(rp.version_detail);'
            'print(scalems.__file__)'
        ],
        'named_env':
        'scalems_env'
    })
    task = tmgr.submit_tasks(td)
    tmgr.wait_tasks()
    logger.debug(f'RP version details and scalems location: {task.stdout}')
    assert task.exit_code == 0
Пример #8
0
def test_rp_raptor_staging(pilot_description, rp_venv):
    """Test file staging for raptor Master and Worker tasks.

    - upon pilot startup, transfer a file to the pilot sandbox
    - upon master startup, create a link to that file for each master
    - for each task, copy the file into the task sandbox
    - upon task completion, transfer the files to the client (and rename them)
    """
    import time
    import radical.pilot as rp

    # Note: we need to install the current scalems package to test remotely.
    # If this is problematic, we can add a check like the following.
    #     if pilot_description.resource != 'local.localhost' \
    #             and pilot_description.access_schema \
    #             and pilot_description.access_schema != 'local':
    #         pytest.skip('This test is only for local execution.')

    # Note: radical.pilot.Session creation causes several deprecation warnings.
    # Ref https://github.com/radical-cybertools/radical.pilot/issues/2185
    with warnings.catch_warnings():
        warnings.simplefilter('ignore', category=DeprecationWarning)
        session = rp.Session()
    fname = '%d.dat' % os.getpid()
    fpath = os.path.join('/tmp', fname)
    data: str = time.asctime()

    # Hopefully, this requirement is temporary.
    if rp_venv is None:
        pytest.skip('This test requires a user-provided static RP venv.')

    if rp_venv:
        pre_exec = ['. {}/bin/activate'.format(rp_venv)]
    else:
        pre_exec = None

    try:
        pmgr = rp.PilotManager(session=session)
        tmgr = rp.TaskManager(session=session)

        # Illustrate data staging as part of the Pilot launch.
        # By default, file is copied to the root of the Pilot sandbox,
        # where it can be referenced as 'pilot:///filename'
        # Alternatively: pilot.stage_in() and pilot.stage_output() (blocking calls)
        pilot_description.exit_on_error = True
        pilot_description.input_staging = [fpath]
        with open(fpath, 'w') as fh:
            fh.writelines([data])
        try:
            pilot = pmgr.submit_pilots(pilot_description)
            # Confirmation that the input file has been staged by waiting for pilot state.
            pilot.wait(state=[rp.states.PMGR_ACTIVE] + rp.FINAL)
        finally:
            os.unlink(fpath)

        tmgr.add_pilots(pilot)

        uid = 'scalems.master.001'
        # Illustrate another mode of data staging with the Master task submission.
        td = rp.TaskDescription({
            'uid':
            uid,
            'executable':
            'scalems_rp_master',
            'input_staging': [{
                'source': 'pilot:///%s' % fname,
                'target': 'pilot:///%s.%s.lnk' % (fname, uid),
                'action': rp.LINK
            }],
            'pre_exec':
            pre_exec
            # 'named_env': 'scalems_env'
        })

        master = tmgr.submit_tasks(td)

        # Illustrate availability of scheduler and of data staged with Master task.
        # When the task enters AGENT_SCHEDULING_PENDING it has passed all input staging,
        # and the files will be available.
        # (see https://docs.google.com/drawings/d/1q5ehxIVdln5tXEn34mJyWAmxBk_DqZ5wwkl3En-t5jo/)

        # Confirm that Master script is running (and ready to receive raptor tasks)
        # WARNING: rp.Task.wait() *state* parameter does not handle tuples, but does not check type.
        master.wait(state=[rp.states.AGENT_EXECUTING] + rp.FINAL)
        assert master.state not in {rp.CANCELED, rp.FAILED}

        # define raptor tasks and submit them to the master
        tds = list()
        # Illustrate data staging as part of raptor task submission.
        # Note that tasks submitted by the client
        # a sandboxed task directory, whereas those submitted by the Master (through Master.request(),
        # through the wrapper script or the Master.create_initial_tasks() hook) do not,
        # and do not have a data staging phase.
        for i in range(3):
            uid = 'scalems.%06d' % i
            work = {
                'mode': 'call',
                'cores': 1,
                'timeout': 10,  # seconds
                'data': {
                    'method': 'hello',
                    'kwargs': {
                        'world': uid
                    }
                }
            }
            tds.append(
                rp.TaskDescription({
                    'uid':
                    uid,
                    'executable':
                    '-',
                    'input_staging': [{
                        'source':
                        'pilot:///%s.%s.lnk' % (fname, master.uid),
                        'target':
                        'task:///%s' % fname,
                        'action':
                        rp.COPY
                    }],
                    'output_staging': [{
                        'source':
                        'task:///%s' % fname,
                        'target':
                        'client:///%s.%s.out' % (fname, uid),
                        'action':
                        rp.TRANSFER
                    }],
                    'scheduler':
                    master.uid,
                    'arguments': [json.dumps(work)],
                    'pre_exec':
                    pre_exec
                }))
        # TODO: Organize client-side data with managed hierarchical paths.
        # Question: RP maintains a filesystem hierarchy on the client side, correct?
        # Answer: only for profiling and such: do not use for data or user-facing stuff.
        tasks = tmgr.submit_tasks(tds)
        # TODO: Clarify the points at which the data exists or is accessed.
        # * When the (client-submitted) task enters AGENT_STAGING_OUTPUT_PENDING,
        #   it has finished executing and output data should be accessible as 'task:///outfile'.
        # * When the (client-submitted) task reaches one of the rp.FINAL stages, it has finished
        #   output staging and files are accessible at the location specified in 'output_staging'.
        # * Tasks submitted directly by the Master (example?) do not perform output staging;
        #   data is written before entering Master.result_cb().
        # RP Issue: client-submitted Tasks need to be accessible through a path that is common
        # with the Master-submitted (`request()`) tasks. (SCALE-MS #108)

        assert len(tasks) == len(tds)
        # 'arguments' (element 0) gets wrapped in a Request at the Master by _receive_tasks,
        # then the list of requests is passed to Master.request(), which is presumably
        # an extension point for derived Master implementations. The base class method
        # converts requests to dictionaries and adds them to a request queue, from which they are
        # picked up by the Worker in _request_cb. Then picked up in forked interpreter
        # by Worker._dispatch, which checks the *mode* of the Request and dispatches
        # according to native or registered mode implementations. (e.g. 'call' (native) or 'scalems')

        # task process is launched with Python multiprocessing (native) module and added to self._pool.
        # When the task runs, it's result triggers _result_cb

        # wait for *those* tasks to complete and report results
        tmgr.wait_tasks(uids=[t.uid for t in tasks])

        # Cancel the master.
        tmgr.cancel_tasks(uids=master.uid)
        # Cancel blocks until the task is done so the following wait it currently redundant,
        # but there is a ticket open to change this behavior.
        # See https://github.com/radical-cybertools/radical.pilot/issues/2336
        tmgr.wait_tasks()

        # Note that these map as follows:
        #     * 'client:///' == $PWD
        #     * 'task:///' == urllib.parse.urlparse(task.sandbox).path
        #     * 'pilot:///' == urllib.parse.urlparse(pilot.pilot_sandbox).path

        for t in tasks:
            print(t)
            outfile = './%s.%s.out' % (fname, t.uid)
            assert os.path.exists(outfile)
            with open(outfile, 'r') as outfh:
                assert outfh.readline().rstrip() == data
            os.unlink(outfile)

        pilot.cancel()
        tmgr.close()
        pmgr.close()

    finally:
        session.close(download=False)
Пример #9
0
async def test_rp_future(rp_task_manager):
    """Check our Future implementation.

    Fulfill the asyncio.Future protocol for a rp.Task wrapper object. The wrapper
    should appropriately yield when the rp.Task is not finished.
    """
    import radical.pilot as rp

    tmgr = rp_task_manager

    td = rp.TaskDescription({
        'executable':
        '/bin/bash',
        'arguments': ['-c', '/bin/sleep 5 && /bin/echo success'],
        'cpu_processes':
        1
    })

    # Test propagation of RP cancellation behavior
    task: rp.Task = tmgr.submit_tasks(td)

    future = asyncio.get_running_loop().create_future()
    wrapper: asyncio.Future = await scalems.radical.rp_task(task, future)

    task.cancel()
    try:
        # TODO: With Python 3.9, check cancellation message for how the cancellation propagated.
        with pytest.raises(asyncio.CancelledError):
            await asyncio.wait_for(wrapper, timeout=120)
    except asyncio.TimeoutError as e:
        # Useful point to insert an easy debugging break point
        raise e

    assert future.cancelled()
    assert wrapper.cancelled()
    assert task.state == rp.states.CANCELED

    # Test propagation of asyncio watcher task cancellation.
    task: rp.Task = tmgr.submit_tasks(td)

    future = asyncio.get_running_loop().create_future()
    wrapper: asyncio.Task = await scalems.radical.rp_task(task, future)

    assert isinstance(wrapper, asyncio.Task)
    wrapper.cancel()
    try:
        with pytest.raises(asyncio.CancelledError):
            await asyncio.wait_for(wrapper, timeout=5)
    except asyncio.TimeoutError as e:
        # Useful point to insert an easy debugging break point
        raise e
    assert wrapper.cancelled()
    assert future.cancelled()

    # WARNING: rp.Task.wait() never completes with no arguments.
    # WARNING: This blocks. Don't do it in the event loop thread.
    task.wait(state=rp.states.CANCELED, timeout=120)
    # Note that if the test is paused by a debugger, the rp task may
    # have a chance to complete before being canceled.
    # Ordinarily, that will not happen in this test.
    # assert task.state in (rp.states.CANCELED, rp.states.DONE)
    assert task.state in (rp.states.CANCELED, )

    # Test propagation of asyncio future cancellation.
    task: rp.Task = tmgr.submit_tasks(td)

    future = asyncio.get_running_loop().create_future()
    wrapper: asyncio.Task = await scalems.radical.rp_task(task, future)

    assert isinstance(wrapper, asyncio.Task)
    future.cancel()
    try:
        with pytest.raises(asyncio.CancelledError):
            await asyncio.wait_for(future, timeout=5)
        await asyncio.wait_for(wrapper, timeout=1)
    except asyncio.TimeoutError as e:
        # Useful point to insert an easy debugging break point
        raise e
    assert not wrapper.cancelled()
    assert future.cancelled()

    # WARNING: rp.Task.wait() never completes with no arguments.
    # WARNING: This blocks. Don't do it in the event loop thread.
    task.wait(state=rp.states.CANCELED, timeout=120)
    # Note that if the test is paused by a debugger, the rp task may
    # have a chance to complete before being canceled.
    # Ordinarily, that will not happen in this test.
    # assert task.state in (rp.states.CANCELED, rp.states.DONE)
    assert task.state in (rp.states.CANCELED, )

    # Test run to completion
    task: rp.Task = tmgr.submit_tasks(td)

    future = asyncio.get_running_loop().create_future()
    wrapper: asyncio.Task = await scalems.radical.rp_task(task, future)

    timeout = 120
    try:
        result = await asyncio.wait_for(future, timeout=timeout)
    except asyncio.TimeoutError as e:
        logger.debug(f'Waited more than {timeout} for {future}: {e}')
        result = None
    assert task.exit_code == 0
    assert 'success' in task.stdout

    assert 'stdout' in result
    assert 'success' in result['stdout']
    assert wrapper.done()
Пример #10
0
def _connect_rp(config: Configuration) -> Runtime:
    """Establish the RP Session.

    Acquire as many re-usable resources as possible. The scope established by
    this function is as broad as it can be within the life of this instance.

    Once instance._connect_rp() succeeds, instance._disconnect_rp() must be called to
    clean up resources. Use the async context manager behavior of the instance to
    automatically follow this protocol. I.e. instead of calling
    ``instance._connect_rp(); ...; instance._disconnect_rp()``,
    use::
        async with instance:
            ...

    Raises:
        DispatchError if task dispatching could not be set up.

        CanceledError if parent asyncio.Task is cancelled while executing.

    """
    # TODO: Consider inlining this into __aenter__().
    # A non-async method is potentially useful for debugging, but causes the event loop
    # to block while waiting for the RP tasks included here. If this continues to be a
    # slow function, we can wrap the remaining RP calls and let this function be
    # inlined, or stick the whole function in a separate thread with
    # loop.run_in_executor().

    # TODO: RP triggers SIGINT in various failure modes.
    #  We should use loop.add_signal_handler() to convert to an exception
    #  that we can raise in an appropriate task.
    # Note that PilotDescription can use `'exit_on_error': False` to suppress the SIGINT,
    # but we have not explored the consequences of doing so.

    try:
        #
        # Start the Session.
        #

        # Note that we cannot resolve the full _resource config until we have a Session
        # object.
        # We cannot get the default session config until after creating the Session,
        # so we don't have a template for allowed, required, or default values.
        # Question: does the provided *cfg* need to be complete? Or will it be merged
        # with default values from some internal definition, such as by dict.update()?
        # I don't remember what the use cases are for overriding the default session
        # config.
        session_config = None
        # At some point soon, we need to track Session ID for the workflow metadata.
        # We may also want Session ID to be deterministic (or to be re-used?).
        session_id = None

        # Note: the current implementation implies that only one Task for the dispatcher
        # will exist at a time. We are further assuming that there will probably only
        # be one Task per the lifetime of the dispatcher object.
        # We could choose another approach and change our assumptions, if appropriate.
        logger.debug(
            'Entering RP dispatching context. Waiting for rp.Session.')

        # Note: radical.pilot.Session creation causes several deprecation warnings.
        # Ref https://github.com/radical-cybertools/radical.pilot/issues/2185
        with warnings.catch_warnings():
            warnings.simplefilter('ignore', category=DeprecationWarning)
            # This would be a good time to `await`, if an event-loop friendly
            # Session creation function becomes available.
            runtime = Runtime(
                session=rp.Session(uid=session_id, cfg=session_config))
        session_id = runtime.session.uid
        # Do we want to log this somewhere?
        # session_config = copy.deepcopy(self.session.cfg.as_dict())
        logger.debug('RP dispatcher acquired session {}'.format(session_id))

        # We can launch an initial Pilot, but we may have to run further Pilots
        # during self._queue_runner_task (or while servicing scalems.wait() within the
        # with block) to handle dynamic work load requirements.
        # Optionally, we could refrain from launching the pilot here, at all,
        # but it seems like a good chance to start bootstrapping the agent environment.
        logger.debug('Launching PilotManager.')
        pilot_manager = rp.PilotManager(session=runtime.session)
        logger.debug('Got PilotManager {}.'.format(pilot_manager.uid))
        runtime.pilot_manager(pilot_manager)

        logger.debug('Launching TaskManager.')
        task_manager = rp.TaskManager(session=runtime.session)
        logger.debug(('Got TaskManager {}'.format(task_manager.uid)))
        runtime.task_manager(task_manager)

        #
        # Get a Pilot
        #

        # # TODO: #94 Describe (link to) configuration points.
        # resource_config['local.localhost'].update({
        #     'project': None,
        #     'queue': None,
        #     'schema': None,
        #     'cores': 1,
        #     'gpus': 0
        # })

        # _pilot_description = dict(_resource=_resource,
        #                          runtime=30,
        #                          exit_on_error=True,
        #                          project=resource_config[_resource]['project'],
        #                          queue=resource_config[_resource]['queue'],
        #                          cores=resource_config[_resource]['cores'],
        #                          gpus=resource_config[_resource]['gpus'])

        # TODO: How to specify PilotDescription? (see also #121)
        # Where should this actually be coming from?
        # We need to inspect both the HPC allocation and the work load, I think,
        # and combine with user-provided preferences.
        pilot_description = {}
        pilot_description.update(
            config.rp_resource_params.get('PilotDescription', {}))
        pilot_description.update({'resource': config.execution_target})

        # TODO: Pilot venv (#90, #94).
        # Currently, Pilot venv must be specified in the JSON file for resource
        # definitions.
        pilot_description = rp.PilotDescription(pilot_description)

        # How and when should we update pilot description?
        logger.debug('Submitting PilotDescription {}'.format(
            repr(pilot_description)))
        pilot = pilot_manager.submit_pilots(pilot_description)
        logger.debug('Got Pilot {}'.format(pilot.uid))
        runtime.pilot(pilot)

        # Note that the task description for the master (and worker) can specify a
        # *named_env* attribute to use a venv prepared via Pilot.prepare_env
        # E.g.         pilot.prepare_env({'numpy_env' : {'type'   : 'virtualenv',
        #                                           'version': '3.6',
        #                                           'setup'  : ['numpy']}})
        #   td.named_env = 'numpy_env'
        # Note that td.named_env MUST be a key that is given to pilot.prepare_env(arg:
        # dict) or the task will wait indefinitely to be scheduled.
        # Alternatively, we could use a pre-installed venv by putting
        # `. path/to/ve/bin/activate`
        # in the TaskDescription.pre_exec list.

        # TODO: Use archives generated from (acquired through) the local installations.
        # # Could we stage in archive distributions directly?
        # # self.pilot.stage_in()
        # pilot.prepare_env(
        #     {
        #         'scalems_env': {
        #             'type': 'virtualenv',
        #             'version': '3.8',
        #             'setup': [
        #                 # TODO: Generalize scalems dependency resolution.
        #                 # Ideally, we would check the current API version
        #                 # requirement, map that to a package version,
        #                 # and specify >=min_version, allowing cached archives to
        #                 # satisfy the dependency.
        #                 rp_spec,
        #                 scalems_spec
        #             ]}})

        # Question: when should we remove the pilot from the task manager?
        task_manager.add_pilots(pilot)
        logger.debug('Added Pilot {} to task manager {}.'.format(
            pilot.uid, task_manager.uid))

        pre_exec = get_pre_exec(config)
        assert isinstance(pre_exec, tuple)
        assert len(pre_exec) > 0
        # Verify usable SCALEMS RP connector.
        # TODO: Fetch a profile of the venv for client-side analysis (e.g. `pip freeze`).
        # TODO: Check for compatible installed scalems API version.
        rp_check = task_manager.submit_tasks(
            rp.TaskDescription({
                # 'executable': py_venv,
                'executable':
                'python3',
                'arguments':
                ['-c', 'import radical.pilot as rp; print(rp.version)'],
                'pre_exec':
                list(pre_exec)
                # 'named_env': 'scalems_env'
            }))
        logger.debug('Checking RP execution environment.')
        states = task_manager.wait_tasks(uids=[rp_check.uid])
        if states[0] != rp.states.DONE or rp_check.exit_code != 0:
            raise DispatchError(
                'Could not verify RP in execution environment.')

        try:
            remote_rp_version = packaging.version.parse(
                rp_check.stdout.rstrip())
        except Exception as e:
            raise DispatchError(
                'Could not determine remote RP version.') from e
        # TODO: #100 Improve compatibility checking.
        if remote_rp_version < packaging.version.parse('1.6.0'):
            raise DispatchError(
                f'Incompatible radical.pilot version in execution '
                f'environment: {str(remote_rp_version)}')

        #
        # Get a scheduler task.
        #

        assert runtime.scheduler is None
        # TODO: #119 Re-enable raptor.
        # runtime.scheduler = _get_scheduler(
        #     'raptor.scalems',
        #     pre_exec=execution_manager._pre_exec,
        #     task_manager=task_manager)
        # Note that we can derive scheduler_name from self.scheduler.uid in later methods.
        # Note: The worker script name only appears in the config file.
        # logger.info('RP scheduler ready.')
        # logger.debug(repr(execution_manager.scheduler))

        return runtime

    except asyncio.CancelledError as e:
        raise e
    except Exception as e:
        logger.exception('Exception while connecting RADICAL Pilot.',
                         exc_info=e)
        raise DispatchError('Failed to launch SCALE-MS master task.') from e