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Joshua Harlow eaad725508 Allow loading conductors via entrypoints

Add an easy to use helper function that is exposed to
fetch a conductor in a way that matches how engines
and persistence backends and jobboards are loaded.

This also adjusts the single threaded conductor to
be now named blocking conductor and exposes an entrypoint
backend fetch() function to load current and future
conductors.

Change-Id: Id146d847c329d3e8510a8f24c3ec8b918680ddb5

2015-02-16 18:30:18 -08:00

2.3 KiB

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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:

Alleviate by:

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).
Resolve the internal error's cause (storage backend failure, other...).
Help implement jobboard garbage binning.

Interfaces

taskflow.conductors.base

Implementations

taskflow.conductors.backends

taskflow.conductors.backends.impl_blocking

Hierarchy

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

2.3 KiB Raw Blame History