plainbox.impl.session.manager – manager for sessions

This module contains glue code that allows one to create and manage sessions and their filesystem presence. It allows SessionState to be de-coupled from SessionStorageRepository, SessionStorage, SessionSuspendHelper and SessionResumeHelper.

class plainbox.impl.session.manager.SessionManager(*args, **kwargs)

Bases: plainbox.impl.pod.POD

Manager class for coupling SessionStorage with SessionState.

This class allows application code to manage disk state of sessions. Using the checkpoint() method applications can create persistent snapshots of the SessionState associated with each SessionManager.

add_device_context(context)

Add a device context to the session manager

Parameters:context – The SessionDeviceContext to add. Raises:ValueError – If the context is already in the session manager or the device represented by that context is already present in the session manager.

This method fires the on_device_context_added() signal

add_local_device_context()

Create and add a SessionDeviceContext that describes the local device.

The local device is always the device executing plainbox. Other devices may execute jobs or parts of plainbox but they don’t need to store or run the full plainbox code.

as_dict() → dict

Return the data in this POD as a dictionary.

Note

UNSET values are not added to the dictionary.

as_tuple() → tuple

Return the data in this POD as a tuple.

Order of elements in the tuple corresponds to the order of field declarations.

checkpoint()

Create a checkpoint of the session.

After calling this method you can later reopen the same session with SessionManager.load_session().

classmethod create(repo=None, prefix='pbox-')

Create an empty session manager.

This method creates an empty session manager. This is the most generic API that allows applications to freely work with any set of devices.

Typically applications will use the add_device_context() method to add additional context objects at a later time. This method creates and populates the session storage with all of the well known directories (using WellKnownDirsHelper.populate()).

Parameters:repo – If specified then this particular repository will be used to create the storage for this session. If left out, a new repository is constructed with the default location. Ptype repo:SessionStorageRepository. Returns:fresh SessionManager instance

create_exporter(exporter_id, option_list=(), strict=True)

Create an exporter object with the specified name and options.

Parameters:

• exporter_id – Identifier of the exporter unit (which must have been loaded into the session device context of the first device). For backwards compatibility this can also be any of the legacy identifiers tar, html, json, text or xlsx.
• option_list – (optional) A list of options to pass to the exporter. Each option is a string. Some strings may be of form ‘key=value’ but those are handled by each exporter separately. By default an empty tuple is used so no special options are enabled.
• strict – (optional) Strict mode, in this mode option_list must not contain any options that are unrecognized by the exporter. Since many options (but not all) are shared among various exporters, using non-strict mode might make it easier to use a single superset of options to all exporters and let them silently ignore those that they don’t understand.

Raises:

LookupError – If the exporter identifier cannot be found. Note that this might indicate that appropriate provider has not been loaded yet.

Returns:

A ISessionStateExporter instance with appropriate configuration.

classmethod create_with_state(state, repo=None)

Create a session manager by wrapping existing session state.

This method populates the session storage with all of the well known directories (using WellKnownDirsHelper.populate())

Parameters:

• stage – A pre-existing SessionState object.
• repo – If specified then this particular repository will be used to create the storage for this session. If left out, a new repository is constructed with the default location.

Ptype repo:

SessionStorageRepository.

Returns:

fresh SessionManager instance

classmethod create_with_unit_list(unit_list=None, repo=None)

Create a session manager with a fresh session.

This method populates the session storage with all of the well known directories (using WellKnownDirsHelper.populate())

Parameters:

• unit_list – If specified then this will be the initial list of units known by the session state object.
• repo – If specified then this particular repository will be used to create the storage for this session. If left out, a new repository is constructed with the default location.

Ptype repo:

SessionStorageRepository.

Returns:

fresh SessionManager instance

default_device_context

The default (first) session device context if available

In single-device sessions this is the context that is used to execute every single job definition. Applications that use multiple devices must access and use the context list directly.

destroy()

Destroy all of the filesystem artifacts of the session.

This basically calls remove()

device_context_list

A list of session device context objects

Note

You must not modify this field directly.

This is not enforced but please use the add_device_context() or remove_device_context() if you want to manipulate the list. Currently you cannot reorder the list of context objects.

Side effects of assign filters:

• type-checked (value must be of type list)
• type-checked sequence (items must be of type SessionDeviceContext)
• constant (read-only after initialization)

exporter_map

Map from exporter id to the corresponding exporter unit.

field_list = [<Field name:'device_context_list'>, <Field name:'storage'>, <Field name:'test_plans'>]

classmethod get_throwaway_manager(provider_list=None)

Create a temporary session manager.

Parameters:provider_list – (optional) A list of providers to put into the session manager. By default all known providers are added. You can use this argument to customize the behaviour beyond defaults. Returns:A new SessionManager object that will be destroyed when the context manager is left.

This method can be used to create a throw-away session manager which is not really meant for running jobs but can be useful to access exporters and other objects stored in providers.

classmethod load_session(unit_list, storage, early_cb=None, flags=None)

Load a previously checkpointed session.

This method allows one to re-open a session that was previously created by SessionManager.checkpoint()

Parameters:

• unit_list – List of all known units. This argument is used to reconstruct the session from a dormant state. Since the suspended data cannot capture implementation details of each unit reliably, actual units need to be provided externally. Unlike in create_session() this list really needs to be complete, it must also include any generated units.
• storage – The storage that should be used for this particular session. The storage object holds references to existing directories in the file system. When restoring an existing dormant session it is important to use the correct storage object, the one that corresponds to the file system location used be the session before it was saved.
• early_cb – A callback that allows the caller to “see” the session object early, before the bulk of resume operation happens. This method can be used to register callbacks on the new session before this method call returns. The callback accepts one argument, session, which is being resumed. This is being passed directly to plainbox.impl.session.resume.SessionResumeHelper.resume()
• flags – An optional set of flags that may influence the resume process. Currently this is an internal implementation detail and no “public” flags are provided. Passing None here is a safe equvalent of using this API before it was introduced.

Ptype storage:

SessionStorage

Raises:

Anything that can be raised by load_checkpoint() and resume()

Returns:

Fresh instance of SessionManager

namedtuple_cls

alias of SessionManager

on_device_context_added

Basic signal that supports arbitrary listeners.

While this class can be used directly it is best used with the helper decorator Signal.define on a function or method. See the documentation for the plainbox.vendor.morris module for details.

Attr _name:Name of the signal, typically accessed via name(). Attr _listeners:  List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener.

on_device_context_removed

Basic signal that supports arbitrary listeners.

While this class can be used directly it is best used with the helper decorator Signal.define on a function or method. See the documentation for the plainbox.vendor.morris module for details.

Attr _name:Name of the signal, typically accessed via name(). Attr _listeners:  List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener.

on_test_plans_changed

Basic signal that supports arbitrary listeners.

While this class can be used directly it is best used with the helper decorator Signal.define on a function or method. See the documentation for the plainbox.vendor.morris module for details.

Attr _name:Name of the signal, typically accessed via name(). Attr _listeners:  List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener.

remove_device_context(context)

Remove an device context from the session manager

Parameters:unit – The SessionDeviceContext to remove.

This method fires the on_device_context_removed() signal

state

SessionState associated with this manager

storage

A SesssionStorage instance

Side effects of assign filters:

• type-checked (value must be of type SessionStorage)
• constant (read-only after initialization)

test_plans

Test plans that this session is processing.

This field contains a tuple of test plans that are active in the session. Any changes here are propagated to each device context participating in the session. This in turn makes all of the overrides defined by those test plans effective.

Note

Currently there is no facitly that would allow to use this field to drive test execution. Such facility is likely to be added later.

Side effects of assign filters:

• type-checked (value must be of type tuple)
• type-checked sequence (items must be of type TestPlanUnit)
• unique elements (sequence elements cannot repeat)

class plainbox.impl.session.manager.WellKnownDirsHelper(*args, **kwargs)

Bases: plainbox.impl.pod.POD

Helper class that knows about well known directories for SessionStorage.

This class simply gets rid of various magic directory names that we associate with session storage. It also provides a convenience utility method populate() to create all of those directories, if needed.

all_directories

a list of all well-known directories

as_dict() → dict

Return the data in this POD as a dictionary.

Note

UNSET values are not added to the dictionary.

as_tuple() → tuple

Return the data in this POD as a tuple.

Order of elements in the tuple corresponds to the order of field declarations.

field_list = [<Field name:'storage'>]

io_log_pathname

full path of the directory where per-job IO logs are stored

namedtuple_cls

alias of WellKnownDirsHelper

populate()

Create all of the well known directories that are expected to exist inside a freshly created session storage directory

storage

SessionStorage associated with this helper

Side effects of assign filters:

• constant (read-only after initialization)
• type-checked (value must be of type SessionStorage)

plainbox.impl.session.manager.at_most_one_context_filter()

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