openstack/taskflow
Code Issues Proposed changes
18d3cd1567
taskflow/doc/source/conductors.rst
Joshua Harlow 17b7c219de Remove link about implementing job garbage binning 
This link is no longer relevant as we now have a
jobboard method that can trash() jobs so that they
can not be claimed again.

Change-Id: I087a90c16b95e9b80a37863fa79f3348fa448bdf
2015-04-01 17:12:38 -07:00

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Conductors

Overview

Conductors in TaskFlow provide a mechanism that unifies the various TaskFlow concepts under a single easy to use (as plug-and-play as we can make it) construct.

They are responsible for the following:

  • Interacting with jobboards <jobs> (examining and claiming jobs <jobs>).
  • Creating engines <engines> from the claimed jobs (using factories <resumption factories> to reconstruct the contained tasks and flows to be executed).
  • Dispatching the engine using the provided persistence <persistence> layer and engine configuration.
  • Completing or abandoning the claimed job (depending on dispatching and execution outcome).
  • Rinse and repeat.

Note

They are inspired by and have similar responsibilities as railroad conductors.

Considerations

Some usage considerations should be used when using a conductor to make sure it's used in a safe and reliable manner. Eventually we hope to make these non-issues but for now they are worth mentioning.

Endless cycling

What: Jobs that fail (due to some type of internal error) on one conductor will be abandoned by that conductor and then another conductor may experience those same errors and abandon it (and repeat). This will create a job abandonment cycle that will continue for as long as the job exists in an claimable state.

Example:

Conductor cycling

Alleviate by:

  1. Forcefully delete jobs that have been failing continuously after a given number of conductor attempts. This can be either done manually or automatically via scripts (or other associated monitoring) or via the jobboards :py~taskflow.jobs.base.JobBoard.trash method.
  2. Resolve the internal error's cause (storage backend failure, other...).

Interfaces

taskflow.conductors.base

Implementations

taskflow.conductors.backends

taskflow.conductors.backends.impl_blocking

Hierarchy

taskflow.conductors.base taskflow.conductors.backends.impl_blocking