Session resume handling.

plainbox.impl.session.resume – session resume handling

This module contains classes that can resume a dormant session from a binary representation. See docs for the suspend module for details.

The resume logic provides a compromise between usefulness and correctness so two assumptions are made:

  • We assume that a checksum of a job changes when their behavior changes. This way we can detect when job definitions were updated after suspending but before resuming.

  • We assume that software and hardware may change while the session is suspended but this is not something that framework (PlainBox) is concerned with. Applications should provide job definitions that are capable of detecting this and acting appropriately.

    This is true since the user may install additional packages or upgrade existing packages. The user can also add or remove pluggable hardware. Lastly actual machine suspend (or hibernate) and resume may cause alterations to the hardware as it is visible from within the system. In any case the framework does not care about this.

exception plainbox.impl.session.resume.BrokenReferenceToExternalFile[source]

Bases: plainbox.impl.session.resume.SessionResumeError

Exception raised when suspended session needs an external file that’s gone.

Exception raised when SessionResumeHelper detects that a file needed by the session to resume is not present. This is typically used to signal inaccessible log files.

args
with_traceback()

Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.

exception plainbox.impl.session.resume.CorruptedSessionError[source]

Bases: plainbox.impl.session.resume.SessionResumeError

Exception raised when suspended session is corrupted.

Exception raised when SessionResumeHelper cannot decode the session byte stream. This exception will be raised with additional context that captures the actual underlying cause. Having this exception class makes it easier to handle resume errors.

args
with_traceback()

Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.

class plainbox.impl.session.resume.EnvelopeUnpackMixIn[source]

Bases: object

A mix-in class capable of unpacking the envelope of the session storage.

This class assists in unpacking the “envelope” in which the session data is actually stored. The envelope is simply gzip but other kinds of envelope can be added later.

unpack_envelope(data)[source]

Unpack the binary envelope and get access to a JSON object.

Parameters:data – Bytes representing the dormant session
Returns:the JSON representation of a session stored in the envelope
Raises:CorruptedSessionError – if the representation of the session is corrupted in any way
exception plainbox.impl.session.resume.IncompatibleJobError[source]

Bases: plainbox.impl.session.resume.SessionResumeError

Exception raised when suspended session needs a different version of a job.

Exception raised when SessionResumeHelper detects that the set of jobs it knows about is incompatible with what was saved before.

args
with_traceback()

Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.

exception plainbox.impl.session.resume.IncompatibleSessionError[source]

Bases: plainbox.impl.session.resume.SessionResumeError

Exception raised when suspended session is correct but incompatible.

Exception raised when SessionResumeHelper comes across malformed or unsupported data that was (presumably) produced by SessionSuspendHelper

args
with_traceback()

Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.

class plainbox.impl.session.resume.MetaDataHelper1MixIn[source]

Bases: object

Mix-in class for working with v1 meta-data.

class plainbox.impl.session.resume.MetaDataHelper2MixIn[source]

Bases: plainbox.impl.session.resume.MetaDataHelper1MixIn

Mix-in class for working with v2 meta-data.

class plainbox.impl.session.resume.MetaDataHelper3MixIn[source]

Bases: plainbox.impl.session.resume.MetaDataHelper2MixIn

Mix-in class for working with v3 meta-data.

class plainbox.impl.session.resume.ResumeDiscardQualifier(retain_id_set)[source]

Bases: plainbox.impl.secure.qualifiers.SimpleQualifier

Qualifier for jobs that need to be discarded after resume.

A job qualifier that designates jobs that should be removed after doing a session resume.

VOTE_EXCLUDE = 0
VOTE_IGNORE = 2
VOTE_INCLUDE = 1
designates(job)
get_primitive_qualifiers()

Return a list of primitives that constitute this qualifier.

Returns:A list of IJobQualifier objects that each is the smallest, indivisible entity. Here it just returns a list of one element, itself.
get_simple_match(job)[source]

Check if a job should be listed by this qualifier.

get_vote(job)

Get one of the VOTE_IGNORE, VOTE_INCLUDE, VOTE_EXCLUDE votes that this qualifier associated with the specified job.

Parameters:job – A IJobDefinition instance that is to be visited
Returns:
  • VOTE_INCLUDE if the job matches the simple qualifier concept embedded into this qualifier and this qualifier is inclusive.
  • VOTE_EXCLUDE if the job matches the simple qualifier concept embedded into this qualifier and this qualifier is not inclusive.
  • VOTE_IGNORE otherwise.
inclusive
is_primitive
origin

Origin of this qualifier

This property can be used to trace the origin of a qualifier back to its definition point.

class plainbox.impl.session.resume.SessionPeekHelper[source]

Bases: plainbox.impl.session.resume.EnvelopeUnpackMixIn

A helper class to peek at session state meta-data quickly.

peek(data)[source]

Peek at the meta-data of a dormant session.

Parameters:

data – Bytes representing the dormant session

Returns:

a SessionMetaData object

Raises:
unpack_envelope(data)

Unpack the binary envelope and get access to a JSON object.

Parameters:data – Bytes representing the dormant session
Returns:the JSON representation of a session stored in the envelope
Raises:CorruptedSessionError – if the representation of the session is corrupted in any way
class plainbox.impl.session.resume.SessionPeekHelper1[source]

Bases: plainbox.impl.session.resume.MetaDataHelper1MixIn

Helper class for implementing session peek feature.

This class works with data constructed by SessionSuspendHelper1 which has been pre-processed by SessionPeekHelper (to strip the initial envelope).

The only goal of this class is to reconstruct session state meta-data.

peek_json(json_repr)[source]

Resume a SessionState object from the JSON representation.

This method is called by peek() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

class plainbox.impl.session.resume.SessionPeekHelper2[source]

Bases: plainbox.impl.session.resume.MetaDataHelper2MixIn, plainbox.impl.session.resume.SessionPeekHelper1

Helper class for implementing session peek feature.

This class works with data constructed by SessionSuspendHelper1 which has been pre-processed by SessionPeekHelper (to strip the initial envelope).

The only goal of this class is to reconstruct session state meta-data.

peek_json(json_repr)

Resume a SessionState object from the JSON representation.

This method is called by peek() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

class plainbox.impl.session.resume.SessionPeekHelper3[source]

Bases: plainbox.impl.session.resume.MetaDataHelper3MixIn, plainbox.impl.session.resume.SessionPeekHelper2

Helper class for implementing session peek feature.

This class works with data constructed by SessionSuspendHelper1 which has been pre-processed by SessionPeekHelper (to strip the initial envelope).

The only goal of this class is to reconstruct session state meta-data.

peek_json(json_repr)

Resume a SessionState object from the JSON representation.

This method is called by peek() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

class plainbox.impl.session.resume.SessionPeekHelper4[source]

Bases: plainbox.impl.session.resume.SessionPeekHelper3

Helper class for implementing session peek feature.

This class works with data constructed by SessionSuspendHelper1 which has been pre-processed by SessionPeekHelper (to strip the initial envelope).

The only goal of this class is to reconstruct session state meta-data.

peek_json(json_repr)

Resume a SessionState object from the JSON representation.

This method is called by peek() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

class plainbox.impl.session.resume.SessionPeekHelper5[source]

Bases: plainbox.impl.session.resume.SessionPeekHelper4

Helper class for implementing session peek feature.

This class works with data constructed by SessionSuspendHelper5 which has been pre-processed by SessionPeekHelper (to strip the initial envelope).

The only goal of this class is to reconstruct session state meta-data.

peek_json(json_repr)

Resume a SessionState object from the JSON representation.

This method is called by peek() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

class plainbox.impl.session.resume.SessionPeekHelper6[source]

Bases: plainbox.impl.session.resume.SessionPeekHelper5

Helper class for implementing session peek feature

This class works with data constructed by SessionSuspendHelper6 which has been pre-processed by SessionPeekHelper (to strip the initial envelope).

The only goal of this class is to reconstruct session state meta-data.

peek_json(json_repr)

Resume a SessionState object from the JSON representation.

This method is called by peek() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

exception plainbox.impl.session.resume.SessionResumeError[source]

Bases: Exception

Base for all session resume exceptions.

Base class for exceptions that can be raised when attempting to resume a dormant session.

args
with_traceback()

Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.

class plainbox.impl.session.resume.SessionResumeHelper[source]

Bases: plainbox.impl.session.resume.EnvelopeUnpackMixIn

Helper class for implementing session resume feature.

This class is a facade that does enough of the resume process to know which version is being resumed and delegate the rest of the process to an appropriate, format specific, resume class.

resume(data, early_cb=None)[source]

Resume a dormant session.

Parameters:
  • data – Bytes representing the dormant session
  • 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 signal listeners on the new session before this method call returns. The callback accepts one argument, session, which is being resumed.
Returns:

resumed session instance

Return type:

SessionState

This method validates the representation of a dormant session and re-creates an identical SessionState instance. It can fail in multiple ways, some of which are a part of normal operation and should always be handled (IncompatibleJobError and IncompatibleJobError). Applications may wish to capture SessionResumeError as a generic base exception for all the possible problems.

Raises:
unpack_envelope(data)

Unpack the binary envelope and get access to a JSON object.

Parameters:data – Bytes representing the dormant session
Returns:the JSON representation of a session stored in the envelope
Raises:CorruptedSessionError – if the representation of the session is corrupted in any way
class plainbox.impl.session.resume.SessionResumeHelper1[source]

Bases: plainbox.impl.session.resume.MetaDataHelper1MixIn

Helper class for implementing session resume feature.

This class works with data constructed by SessionSuspendHelper1 which has been pre-processed by SessionResumeHelper (to strip the initial envelope).

Due to the constraints of what can be represented in a suspended session, this class cannot work in isolation. It must operate with a list of know jobs.

Since (most of the) jobs are being provided externally (as they represent the non-serialized parts of checkbox or other job providers) several failure modes are possible. Those are documented in resume()

FLAG_FILE_REFERENCE_CHECKS_F = 1
FLAG_FILE_REFERENCE_CHECKS_S = 'file-reference-checks'
FLAG_IGNORE_JOB_CHECKSUMS_F = 4
FLAG_IGNORE_JOB_CHECKSUMS_S = 'ignore-job-checksums'
FLAG_REWRITE_LOG_PATHNAMES_F = 2
FLAG_REWRITE_LOG_PATHNAMES_S = 'rewrite-log-pathnames'
resume_json(json_repr, early_cb=None)[source]

Resume a SessionState object from the JSON representation.

This method is called by resume() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

class plainbox.impl.session.resume.SessionResumeHelper2[source]

Bases: plainbox.impl.session.resume.MetaDataHelper2MixIn, plainbox.impl.session.resume.SessionResumeHelper1

Helper class for implementing session resume feature.

This class works with data constructed by SessionSuspendHelper2 which has been pre-processed by SessionResumeHelper (to strip the initial envelope).

Due to the constraints of what can be represented in a suspended session, this class cannot work in isolation. It must operate with a list of know jobs.

Since (most of the) jobs are being provided externally (as they represent the non-serialized parts of checkbox or other job providers) several failure modes are possible. Those are documented in resume()

FLAG_FILE_REFERENCE_CHECKS_F = 1
FLAG_FILE_REFERENCE_CHECKS_S = 'file-reference-checks'
FLAG_IGNORE_JOB_CHECKSUMS_F = 4
FLAG_IGNORE_JOB_CHECKSUMS_S = 'ignore-job-checksums'
FLAG_REWRITE_LOG_PATHNAMES_F = 2
FLAG_REWRITE_LOG_PATHNAMES_S = 'rewrite-log-pathnames'
resume_json(json_repr, early_cb=None)

Resume a SessionState object from the JSON representation.

This method is called by resume() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

class plainbox.impl.session.resume.SessionResumeHelper3[source]

Bases: plainbox.impl.session.resume.MetaDataHelper3MixIn, plainbox.impl.session.resume.SessionResumeHelper2

Helper class for implementing session resume feature.

This class works with data constructed by SessionSuspendHelper3 which has been pre-processed by SessionResumeHelper (to strip the initial envelope).

Due to the constraints of what can be represented in a suspended session, this class cannot work in isolation. It must operate with a list of know jobs.

Since (most of the) jobs are being provided externally (as they represent the non-serialized parts of checkbox or other job providers) several failure modes are possible. Those are documented in resume()

FLAG_FILE_REFERENCE_CHECKS_F = 1
FLAG_FILE_REFERENCE_CHECKS_S = 'file-reference-checks'
FLAG_IGNORE_JOB_CHECKSUMS_F = 4
FLAG_IGNORE_JOB_CHECKSUMS_S = 'ignore-job-checksums'
FLAG_REWRITE_LOG_PATHNAMES_F = 2
FLAG_REWRITE_LOG_PATHNAMES_S = 'rewrite-log-pathnames'
resume_json(json_repr, early_cb=None)

Resume a SessionState object from the JSON representation.

This method is called by resume() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

class plainbox.impl.session.resume.SessionResumeHelper4[source]

Bases: plainbox.impl.session.resume.SessionResumeHelper3

Helper class for implementing session resume feature.

This class works with data constructed by SessionSuspendHelper4 which has been pre-processed by SessionResumeHelper (to strip the initial envelope).

Due to the constraints of what can be represented in a suspended session, this class cannot work in isolation. It must operate with a list of know jobs.

Since (most of the) jobs are being provided externally (as they represent the non-serialized parts of checkbox or other job providers) several failure modes are possible. Those are documented in resume()

FLAG_FILE_REFERENCE_CHECKS_F = 1
FLAG_FILE_REFERENCE_CHECKS_S = 'file-reference-checks'
FLAG_IGNORE_JOB_CHECKSUMS_F = 4
FLAG_IGNORE_JOB_CHECKSUMS_S = 'ignore-job-checksums'
FLAG_REWRITE_LOG_PATHNAMES_F = 2
FLAG_REWRITE_LOG_PATHNAMES_S = 'rewrite-log-pathnames'
resume_json(json_repr, early_cb=None)

Resume a SessionState object from the JSON representation.

This method is called by resume() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

class plainbox.impl.session.resume.SessionResumeHelper5[source]

Bases: plainbox.impl.session.resume.SessionResumeHelper4

Helper class for implementing session resume feature.

This class works with data constructed by SessionSuspendHelper5 which has been pre-processed by SessionResumeHelper (to strip the initial envelope).

Due to the constraints of what can be represented in a suspended session, this class cannot work in isolation. It must operate with a list of know jobs.

Since (most of the) jobs are being provided externally (as they represent the non-serialized parts of checkbox or other job providers) several failure modes are possible. Those are documented in resume()

FLAG_FILE_REFERENCE_CHECKS_F = 1
FLAG_FILE_REFERENCE_CHECKS_S = 'file-reference-checks'
FLAG_IGNORE_JOB_CHECKSUMS_F = 4
FLAG_IGNORE_JOB_CHECKSUMS_S = 'ignore-job-checksums'
FLAG_REWRITE_LOG_PATHNAMES_F = 2
FLAG_REWRITE_LOG_PATHNAMES_S = 'rewrite-log-pathnames'
resume_json(json_repr, early_cb=None)

Resume a SessionState object from the JSON representation.

This method is called by resume() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

class plainbox.impl.session.resume.SessionResumeHelper6[source]

Bases: plainbox.impl.session.resume.SessionResumeHelper5

Helper class for implementing session resume feature

This class works with data constructed by SessionSuspendHelper5 which has been pre-processed by SessionResumeHelper (to strip the initial envelope).

Due to the constraints of what can be represented in a suspended session, this class cannot work in isolation. It must operate with a list of know jobs.

Since (most of the) jobs are being provided externally (as they represent the non-serialized parts of checkbox or other job providers) several failure modes are possible. Those are documented in resume()

FLAG_FILE_REFERENCE_CHECKS_F = 1
FLAG_FILE_REFERENCE_CHECKS_S = 'file-reference-checks'
FLAG_IGNORE_JOB_CHECKSUMS_F = 4
FLAG_IGNORE_JOB_CHECKSUMS_S = 'ignore-job-checksums'
FLAG_REWRITE_LOG_PATHNAMES_F = 2
FLAG_REWRITE_LOG_PATHNAMES_S = 'rewrite-log-pathnames'
resume_json(json_repr, early_cb=None)

Resume a SessionState object from the JSON representation.

This method is called by resume() after the initial envelope and parsing is done. The only error conditions that can happen are related to semantic incompatibilities or corrupted internal state.

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