Job Dependency Solver.

plainbox.impl.depmgr

Warning

THIS MODULE DOES NOT HAVE STABLE PUBLIC API

class plainbox.impl.depmgr.Color

Bases: plainbox.vendor.enum.Enum

Three classic colors for recursive graph visitor.

WHITE:

For nodes have not been visited yet.

GRAY:

For nodes that are currently being visited but the visit is not complete.

BLACK:

For nodes that have been visited and are complete.

BLACK = <Color.BLACK: 'black'>

GRAY = <Color.GRAY: 'gray'>

WHITE = <Color.WHITE: 'white'>

exception plainbox.impl.depmgr.DependencyCycleError(job_list)

Bases: plainbox.impl.depmgr.DependencyError

Exception raised when a cyclic dependency is detected.

affected_job

job that is affected by the dependency error.

Here it is the job that has a cyclic dependency on itself.

affecting_job

job that is affecting the affected_job.

Here it’s always the same as affected_job

args

with_traceback()

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

exception plainbox.impl.depmgr.DependencyDuplicateError(job, duplicate_job)

Bases: plainbox.impl.depmgr.DependencyError

Exception raised when two jobs have the same id.

affected_job

job that is affected by the dependency error.

Here it is the job that is already known by the system.

affecting_job

job that is affecting the affected_job.

Here it is the job that is clashing with another job already present in the system.

args

with_traceback()

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

exception plainbox.impl.depmgr.DependencyError

Bases: builtins.Exception

Exception raised when a dependency error is detected.

affected_job

job that is affected by the dependency error.

affecting_job

job that is affecting the affected_job.

This may be None in certain cases (eg, when the job does not exist and is merely referred to by id). If this job exists removing it SHOULD fix this problem from occurring.

This may be the same as affected_job

args

with_traceback()

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

exception plainbox.impl.depmgr.DependencyMissingError(job, missing_job_id, dep_type)

Bases: plainbox.impl.depmgr.DependencyError

Exception raised when a job has an unsatisfied dependency.

DEP_TYPE_DIRECT = 'direct'

DEP_TYPE_RESOURCE = 'resource'

affected_job

job that is affected by the dependency error.

Here it is the job that has a missing dependency.

affecting_job

job that is affecting the affected_job.

Here it is always None as we have not seen this job at all and that’s what’s causing the problem in the first place.

args

with_traceback()

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

class plainbox.impl.depmgr.DependencySolver(job_list)

Bases: builtins.object

Dependency solver for Jobs.

Uses a simple depth-first search to discover the sequence of jobs that can run. Use the resolve_dependencies() class method to get the solution.

COLOR_BLACK = <Color.BLACK: 'black'>

COLOR_GRAY = <Color.GRAY: 'gray'>

COLOR_WHITE = <Color.WHITE: 'white'>

classmethod resolve_dependencies(job_list, visit_list=None)

Solve the dependency graph expressed as a list of job definitions.

Parameters:

• job_list (list) – list of known jobs
• visit_list (list) – (optional) list of jobs to solve

The visit_list, if specified, allows to consider only a part of the graph while still having access and knowledge of all jobs.

Returns list:

the solution (a list of jobs to execute in order)

Raises:

• DependencyDuplicateError – if a duplicate job definition is present
• DependencyCycleError – if a cyclic dependency is present.
• DependencyMissingErorr – if a required job does not exist.

exception plainbox.impl.depmgr.DependencyUnknownError(job)

Bases: plainbox.impl.depmgr.DependencyError

Exception raised when an unknown job is mentioned.

Note

This class differs from DependencyMissingError in that the unknown job is not a dependency of anything. It can only happen when the job is explicitly mentioned in the list of jobs to visit.

affected_job

job that is affected by the dependency error.

Here it’s a job that on the visit_list but not on the job_list.

affecting_job

job that is affecting the affected_job.

Here, it is always None.

args

with_traceback()

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