Sessions are central state holders and one of the most important classes in PlainBox. Since they are all named alike it’s a bit hard to find what the actual responsibilities are. Here’s a small shortcut, do read the description of each module and class for additional details though.
This a class that holds all of the state and program logic. It SessionManager is a class that couples SessionState and SessionStorage. It has the methods required to alter the state by introducing additional jobs or results. It’s main responsibility is to keep track of all of the jobs, their results, if they are runnable or not (technically what is preventing them from being runnable) and to compute the order of execution that can satisfy all of the dependencies.
It holds a number of references to other pieces of PlainBox (jobs, resources and other things) but one thing stands out. This class holds references to a number of JobState objects that couple a JobResult and JobDefinition together.
This class is a subclass of SessionState with additional methods for suspend and resume. It should not be used in new applications and it will be removed eventually, once the new manager-based API settles in. There are two classes that actually implement this API, one based on the original implementation and another one based on the new implementation. The data they create is not compatible with each other. Currently the original implementation is used. This will change very soon.
A coupling class between JobDefinition and JobResult. This class also knows why a job cannot be started in a particular session, by maintaining a set of “inhibitors” that prevent it from being runnable. The actual inhibitors are managed by SessionState.
This class knows how properly to save and load bytes and manages a directory for all the filesystem entries associated with a particular session. It holds no references to a session though. Typically the class is not instantiated directly but instead comes from helper methods of SessionStorageRepository.
This class knows how to enumerate possible instances of SessionStorage from a given location in the filesystem. It also knows how to obtain a default location using XDG standards.
Bases: plainbox.impl.pod.POD
Class representing the cause of a job not being ready to execute.
It is intended to be consumed by UI layers and to provide them with enough information to render informative error messages or other visual feedback that will aid the user in understanding why a job cannot be started.
There are four possible not ready causes:
- UNDESIRED:
- This job was not selected to run in this session
- PENDING_DEP:
- This job depends on another job which was not started yet
- FAILED_DEP:
- This job depends on another job which was started and failed
- PENDING_RESOURCE:
- This job has a resource requirement expression that uses a resource produced by another job which was not started yet
- FAILED_RESOURCE:
- This job has a resource requirement that evaluated to a false value
All causes apart from UNDESIRED use the related_job property to encode a job that is related to the problem. The PENDING_RESOURCE and FAILED_RESOURCE causes also store related_expression that describes the relevant requirement expression.
There are three attributes that can be accessed:
- cause:
- Encodes the reason why a job is not ready, see InhibitionCause.
- related_job:
- Provides additional context for the problem. This is not the job that is affected, rather, the job that is causing the problem.
- related_expression:
- Provides additional context for the problem caused by a failing resource expression.
Return the data in this POD as a dictionary
Return the data in this POD as a tuple.
Order of elements in the tuple corresponds to the order of field declarations.
cause (constant) of the inhibitor
alias of JobReadinessInhibitor
an (optional) resource expression reference
an (optional) job reference
Bases: plainbox.impl.pod.POD
Class representing the state of a job in a session.
Contains the following basic properties of each job:
- the readiness_inhibitor_list that prevent the job form starting
- the result (outcome) of the run (IJobResult)
- the effective category identifier
- the effective certification status
- the job that was used to create it (via_job)
For convenience (to SessionState implementation) it also has a reference to the job itself. This class is a pure state holder an will typically collaborate with the SessionState class and the UI layer.
Apply overrides to effective jop values.
This method is automatically called by SessionDeviceContext to implement effective overrides originating from test plan data.
Parameters: | override_list – A list, as exposed by values of TestPlanUnitSupport.override_list, composed of a sequence of pairs (field, value), where field is the name of the field to override (without the prefix effective_) and value is any valid value of that field. |
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Raises: |
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Note
Consult field specification for details on what types and values are valid for that field.
Example:
>>> from plainbox.vendor.mock import Mock
>>> job = Mock(spec=JobDefinition)
>>> job_state = JobState(job)
>>> job_state.apply_overrides([
... ('category_id', 'new-category-id'),
... ('certification_status', 'blocker')])
>>> job_state.effective_category_id
'new-category-id'
>>> job_state.effective_certification_status
'blocker'
Return the data in this POD as a dictionary
Return the data in this POD as a tuple.
Order of elements in the tuple corresponds to the order of field declarations.
Quickly check if the associated job can run right now.
the effective categorization of this test in a session
the effective certification status of this job
Get a human readable description of the current readiness state
the job associated with this state
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(). |
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Attr _listeners: | |
List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener. |
the list of readiness inhibitors of the associated job
the result of running the associated job
the parent job definition
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 a device context to the session manager
Parameters: | context – The SessionDeviceContext to add. |
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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
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.
Return the data in this POD as a dictionary
Return the data in this POD as a tuple.
Order of elements in the tuple corresponds to the order of field declarations.
Create a checkpoint of the session.
After calling this method you can later reopen the same session with SessionManager.load_session().
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: |
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Ptype repo: | |
Ptype legacy_mode: | |
bool |
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Returns: | fresh SessionManager instance |
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: |
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Ptype repo: | |
Ptype legacy_mode: | |
bool |
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Returns: | fresh SessionManager instance |
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: |
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Ptype repo: | |
Ptype legacy_mode: | |
bool |
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Returns: | fresh SessionManager instance |
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.
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.
Load a previously checkpointed session.
This method allows one to re-open a session that was previously created by SessionManager.checkpoint()
Parameters: |
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Ptype storage: | |
Raises: | Anything that can be raised by load_checkpoint() and resume() |
Returns: | Fresh instance of SessionManager |
alias of SessionManager
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(). |
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Attr _listeners: | |
List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener. |
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(). |
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Attr _listeners: | |
List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener. |
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(). |
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Attr _listeners: | |
List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener. |
Remove an device context from the session manager
Parameters: | unit – The SessionDeviceContext to remove. |
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This method fires the on_device_context_removed() signal
SessionState associated with this manager
A SesssionStorage instance
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.
Bases: builtins.object
Class representing non-critical state of the session.
The data held here allows applications to reason about sessions in general but is not relevant to the runner or the core in general
Custom, application specific binary blob.
The type and value of this property is irrelevant as it is not inspected by plainbox at all. Reasonable applications will not make use of this property for storing large amounts of data. If you are tempted to do that, please redesign your application or propose changes to plainbox.
Application identifier
A string identifying the application that stored app_blob. It is recommended to use reverse domain names or UUIDs.
a set of flags that are associated with this session.
This set is persisted by persistent_save() and can be used to keep track of how the application wants to interpret this session state.
Intended usage is to keep track of “testing finished” and “results submitted” flags. Some flags are added as constants to this class.
id of the running job
Note
This property has a confusing name. It actually refers to job ID, not name.
This property should be updated to keep track of the name of the job that is being executed. When either plainbox or the machine it was running on crashes during the execution of a job this value should be preserved and can help the GUI to resume and provide an error message.
The property MUST be set before starting the job itself.
the session title.
Title is just an arbitrary string that can be used to distinguish between multiple sessions.
The value can be changed at any time.
Bases: plainbox.impl.session.resume.EnvelopeUnpackMixIn
Peek at the meta-data of a dormant session.
Parameters: | data – Bytes representing the dormant session |
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Returns: | a SessionMetaData object |
Raises: |
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Unpack the binary envelope and get access to a JSON object
Parameters: | data – Bytes representing the dormant session |
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Returns: | the JSON representation of a session stored in the envelope |
Raises CorruptedSessionError: | |
if the representation of the session is corrupted in any way |
Bases: builtins.Exception
Base class for exceptions that can be raised when attempting to resume a dormant session.
Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.
Bases: builtins.object
Class representing all state needed during a single program session.
This is the central glue/entry-point for applications. It connects user intents to the rest of the system / plumbing and keeps all of the state in one place.
The set of utility methods and properties allow applications to easily handle the lower levels of dependencies, resources and ready states.
SessionState has the following instance variables, all of which are currently exposed as properties.
Variables: |
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Add a new job to the session
Parameters: |
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Returns: | The job that was actually added or an existing, identical job if a perfect clash was silently ignored. |
Raises DependencyDuplicateError: | |
if a duplicate, clashing job definition is detected |
The new_job gets added to all the state tracking objects of the session. The job is initially not selected to run (it is not in the desired_job_list and has the undesired inhibitor).
The new_job may clash with an existing job with the same id. Unless both jobs are identical this will cause DependencyDuplicateError to be raised. Identical jobs are silently discarded.
Note
This method recomputes job readiness for all jobs
Deprecated since version 0.9: use the add_unit() method instead
Add a new unit to the session
Parameters: |
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Returns: | The unit that was actually added or an existing, identical unit if a perfect clash was silently ignored. |
Raises DependencyDuplicateError: | |
if a duplicate, clashing job definition is detected |
Note
The following applies only to newly added job units:
The new_unit gets added to all the state tracking objects of the session. The job unit is initially not selected to run (it is not in the desired_job_list and has the undesired inhibitor).
The new_unit job may clash with an existing job with the same id. Unless both jobs are identical this will cause DependencyDuplicateError to be raised. Identical jobs are silently discarded.
Note
This method recomputes job readiness for all jobs unless the recompute=False argument is used. Recomputing takes a while so if you want to add a lot of units consider setting that to False and only recompute at the last call.
List of jobs that are on the “desired to run” list
This is a list, not a set, because the dependency solver algorithm retains as much of the original ordering as possible. Having said that, the actual order can differ widely (for instance, be reversed)
Provide the estimated duration of the jobs that have been selected to run in this session (maintained by calling update_desired_job_list).
Manual jobs have an arbitrary figure added to their runtime to allow for execution of the test steps and verification of the result.
Returns: | (estimate_automated, estimate_manual) |
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where estimate_automated is the value for automated jobs only and estimate_manual is the value for manual jobs only. These can be easily combined. Either value can be None if the value could not be calculated due to any job lacking the required estimated_duration field.
List of all known jobs.
Not necessarily all jobs from this list can be, or are desired to run. For API simplicity this variable is read-only, if you wish to alter the list of all jobs re-instantiate this class please.
Map from job id to JobState that encodes the state of each job.
metadata object associated with this session state.
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(). |
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Attr _listeners: | |
List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener. |
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(). |
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Attr _listeners: | |
List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener. |
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(). |
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Attr _listeners: | |
List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener. |
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(). |
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Attr _listeners: | |
List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener. |
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(). |
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Attr _listeners: | |
List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener. |
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(). |
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Attr _listeners: | |
List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener. |
Remove an existing unit from the session
Parameters: |
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Note
This method recomputes job readiness for all jobs unless the recompute=False argument is used. Recomputing takes a while so if you want to add a lot of units consider setting that to False and only recompute at the last call.
Map from resource id to a list of resource records
List of jobs that were intended to run, in the proper order
The order is a result of topological sorting of the desired_job_list. This value is recomputed when change_desired_run_list() is called. It may be shorter than desired_run_list due to dependency errors.
Add or change a resource with the given id.
Resources silently overwrite any old resources with the same id.
Discard jobs that are selected by the given qualifier.
Parameters: | qualifier – A qualifier that selects jobs to be removed |
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Ptype qualifier: | |
IJobQualifier | |
Raises ValueError: | |
If any of the jobs selected by the qualifier is on the desired job list (or the run list) |
This function correctly and safely discards certain jobs from the job list. It also removes the associated job state (and referenced job result) and results (for jobs that were resource jobs)
List of all known units
Update the set of desired jobs (that ought to run)
This method can be used by the UI to recompute the dependency graph. The argument ‘desired_job_list’ is a list of jobs that should run. Those jobs must be a sub-collection of the job_list argument that was passed to the constructor.
It never fails although it may reduce the actual permitted desired_job_list to an empty list. It returns a list of problems (all instances of DependencyError class), one for each job that had to be removed.
Notice the specified test result and update readiness state.
This function updates the internal result collection with the data from the specified test result. Results can safely override older results. Results also change the ready map (jobs that can run) because of dependency relations.
Some results have deeper meaning, those are results for local and resource jobs. They are discussed in detail below:
Resource jobs produce resource records which are used as data to run requirement expressions against. Each time a result for a resource job is presented to the session it will be parsed as a collection of RFC822 records. A new entry is created in the resource map (entirely replacing any old entries), with a list of the resources that were parsed from the IO log.
Local jobs produce more jobs. Like with resource jobs, their IO log is parsed and interpreted as additional jobs. Unlike in resource jobs local jobs don’t replace anything. They cannot replace an existing job with the same id.
alias of SessionStateLegacyAPICompatImpl
Bases: builtins.object
Abstraction for storage area that is used by SessionState to keep some persistent and volatile data.
This class implements functions performing input/output operations on session checkpoint data. The location property can be used for keeping any additional files or directories but keep in mind that they will be removed by SessionStorage.remove()
This class indirectly collaborates with SessionSuspendHelper and SessionResumeHelper.
Forcibly unlock the storage by removing a file created during atomic filesystem operations of save_checkpoint().
This method might be useful if save_checkpoint() raises LockedStorageError. It removes the “next” file that is used for atomic rename.
Create a new SessionStorage in a random subdirectory of the specified base directory. The base directory is also created if necessary.
Parameters: |
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Note
Legacy mode is where applications using PlainBox API can only handle one session. Creating another session replaces whatever was stored before. In non-legacy mode applications can enumerate sessions, create arbitrary number of sessions at the same time and remove sessions once they are no longer necessary.
Legacy mode is implemented with a symbolic link called ‘last-session’ that keeps track of the last session created using legacy_mode=True. When a new legacy-mode session is created the target of that symlink is read and recursively removed.
identifier of the session storage (name of the random directory)
Load checkpoint data from the filesystem
Returns: | data from the most recent checkpoint |
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Return type: | bytes |
Raises: |
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location of the session storage
Remove all filesystem entries associated with this instance.
Save checkpoint data to the filesystem.
The directory associated with this SessionStorage must already exist. Typically the instance should be obtained by calling SessionStorage.create() which will ensure that this is already the case.
Raises: |
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pathname of the session state file
Bases: builtins.object
Helper class to enumerate filesystem artefacts of current or past Sessions
This class collaborates with SessionStorage. The basic use-case is to open a well-known location and enumerate all the sessions that are stored there. This allows to create SessionStorage instances to further manage each session (such as remove them by calling :meth:SessionStorage.remove()`)
Get the default location of the session state repository
The default location is defined by $PLAINBOX_SESSION_REPOSITORY which must be a writable directory (created if needed) where plainbox will keep its session data. The default location, if the environment variable is not provided, is ${XDG_CACHE_HOME:-$HOME/.cache}/plainbox/sessions
Find the last session storage object created in this repository.
Returns: | SessionStorage object associated with the last session created in this repository using legacy mode. |
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Note
This will only return storage objects that were created using legacy mode. Nonlegacy storage objects will not be returned this way.
Enumerate stored sessions in the repository.
If the repository directory is not present then an empty list is returned.
Returns: | list of SessionStorage representing discovered sessions |
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pathname of the repository
Bases: plainbox.vendor.enum.IntEnum
There are four possible not-ready causes:
- UNDESIRED:
- This job was not selected to run in this session
- PENDING_DEP:
- This job depends on another job which was not started yet
- FAILED_DEP:
- This job depends on another job which was started and failed
- PENDING_RESOURCE:
- This job has a resource requirement expression that uses a resource produced by another job which was not started yet
- FAILED_RESOURCE:
- This job has a resource requirement that evaluated to a false value