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Difference between revisions of "StructuredStateManagement"

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== Summary ==
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Drafter:  [[Harlowja]]
  
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Move away from ad-hoc states and state transitions to a more concrete organized structured state management in nova.
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Revised on: {{REVISIONMONTH1}}/{{REVISIONDAY}}/{{REVISIONYEAR}} by {{REVISIONUSER}}
  
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=== What problems does this solve ===
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=== Rationale ===
  
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* Increases the [stability, extendability, reliability] of nova.
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Move away from ad-hoc states and state transitions for resource acquisition and modification to a more well-defined organized state management system. This new state management system will have advanced new & shiny features such as greater stability, automatic recovery mechanisms and greater scalability than what currently exists (and more!).
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* Makes it easier to [debug, test, understand, verify, review] nova code.
 
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* Removes hard to discover state-transition dependencies and interactions with clearly defined state-transition dependencies and interactions.
 
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* Ensures state transitions are done reliably and correctly by isolating those transitions to a single place.
 
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* Removes the need for periodic tasks to cleanup ''garbage'' left by nova's ad-hoc states.
 
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* Fixes a variety of problems that previously had piecemeal like patches applied.
 
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* Eliminates the inherent  fragility of a ad-hoc workflow.
 
  
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==== Issues that would likely not have happened with a better state management system ====
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=== Definitions ===
  
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Examples include:
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;State
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# Varying exceptions
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: The particular condition that someone or something is in at a specific time: "the state of the instance request".
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# MQ timeouts
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;State transition
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# DB timeouts
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: Altering a state by applying a function on-top of that state (of which said function may take inputs and provide outputs) resulting in a new state.
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# WS call timeouts
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;Task
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: The application of a state transition on a given state.
 +
;Workflow
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: The sequence of administrative/other processes through which a piece of work passes from initiation to completion.
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;State management engine
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: An individual or entity that arranges or control the elements of, as to achieve a desired overall effect.
  
 +
=== What problems is this attempting to solve ===
  
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Bugs/blueprints that likely would not be needed:
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* Increasing the ['extendability', 'recoverability', 'reliability', 'stability'] of states and state transitions.
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# https://blueprints.launchpad.net/nova/+spec/compute-instance-cleanup-service
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* Making it easier to [ 'add', 'debug', 'review', 'test', 'understand', 'verify'] existing & new states and state transitions.
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# https://bugs.launchpad.net/nova/+bug/1050979
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* Removing hard to discover state & transition dependencies and interactions.
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# https://bugs.launchpad.net/nova/+bug/1061024
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* Ensuring state transitions are done ['correctly', 'reliably'] by isolating those transitions to a entity whose exclusive responsibility is to ['correctly', 'reliably'] perform said transitions.
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# https://bugs.launchpad.net/nova/+bug/1082414
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* Fixing a variety of problems that previously had piecemeal like patches applied to solve them.
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# ...
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* Eliminating the inherent ''fragility'' of the current ad-hoc workflows.
 +
* Allows for upgrading a cloud/software with inflight actions without needing later manual cleanup of said  actions.
 +
* Makes it possible to audit & track the state transitions performed on a given resource in a unified manner.
 +
** '''Note:''' that there currently exists notifications, logging, event reporting as different mechanisms (which are not used in a uniform manner).
 +
* Removes the need for certain types of periodic tasks which start to consume more and more resources as  you grow your cluster larger.
 +
* Moves toward the path where actions will automatically recover on ''cutting'' events (node failure, resource failure, network failure..).
 +
* Removes the need for periodic tasks to cleanup ''garbage'' (orphaned instances/resources/tasks...) left behind.
 +
* Creates the foundation for a more reliable and automatic recovery process when errors do occur.
 +
* Encourages the ['altering', 'extension'] of default workflows with a more ['complex', 'custom', 'experimental'] workflows.
  
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=== Requirements ===
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==== Fixing a known need ====
  
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https://etherpad.openstack.org/task-system
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* https://blueprints.launchpad.net/nova/+spec/compute-instance-cleanup-service
 +
* https://blueprints.launchpad.net/cinder/+spec/cinder-state-machine
 +
* https://bugs.launchpad.net/nova/+bug/1173408
 +
* https://bugs.launchpad.net/nova/+bug/1173413
 +
* https://bugs.launchpad.net/nova/+bug/1173417
 +
* https://bugs.launchpad.net/nova/+bug/1173420
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* https://bugs.launchpad.net/nova/+bug/1050979
 +
* https://bugs.launchpad.net/nova/+bug/1061024
 +
* https://bugs.launchpad.net/nova/+bug/1082414
 +
* https://bugs.launchpad.net/nova/+bug/1173429
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* https://bugs.launchpad.net/nova/+bug/1173430
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* (and more)
  
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=== Discussions ===
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=== Blueprints ===
  
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https://etherpad.openstack.org/the-future-of-orch
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* https://blueprints.launchpad.net/nova/+spec/structured-state-management
 +
* https://blueprints.launchpad.net/cinder/+spec/cinder-state-machine
  
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=== Plan of record ===
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=== Related papers ===
−
 
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# Create prototype.
 
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# Get feedback from summit session.
 
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# Get more feedback from email list & heat folks about common library.
 
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# Adjust prototype as needed from feedback.
 
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# Split prototype into small chunks.
 
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# Adjust tests for each small chunks.
 
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# Start to submit prototype chunks into http://review.openstack.org (disabling whole/pieces component until ready to turn on?).
 
  
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== Design ==
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* http://www.netdb.cis.upenn.edu/papers/tropic_tr.pdf
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[[File:New-arch.png|thumbnail|center]]
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* http://research.microsoft.com/pubs/64604/osr2007.pdf
  
 +
=== Related wikis ===
  
 +
* https://wiki.openstack.org/wiki/Convection
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* https://wiki.openstack.org/wiki/NovaOrchestration/WorkflowEngines ('''old''')
  
 +
=== Potential Requirements ===
  
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=== Design details ===
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https://etherpad.openstack.org/task-system
  
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In order to implement of this new orchestration layer the following key concepts must be built into the design from the start.
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=== Summit Discussions ===
  
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# A set of '''atomic''' tasks that can be organized into a workflow.
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'''Havana summit:'''
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# Task resumption.
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* https://etherpad.openstack.org/the-future-of-orch
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# Task rollback.
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* https://etherpad.openstack.org/Summit-Havana-Cinder-Safe-Shutdown
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# Task tracking.
 
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# Resource locking.
 
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# Workflow sharding/ownership.
 
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# Simplicity (allowing for extension and verifiability).
 
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# Tolerant to upgrades.
 
  
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==== Atomic tasks ====
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=== Plan of record ===
 +
 +
==== Step 1 ====
  
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===== Why it matters =====
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'''Create prototype'''
  
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===== How it will be addressed =====
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# Create core workflow/task library and prototype using said library in nova for ''run_instance'' action.
 +
# Split this action (refactored) into small atomic task chunks (don't aim for perfection just yet, since its a prototype).
 +
# Organize chunks into a workflow and test workflow.
 +
# Show working prototype at summit session (with associated docs...)
  
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==== Task resumption ====
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==== Step 2 ====
  
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===== Why it matters =====
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# Get feedback on prototype from people involved in making it + other interested parties.
 +
# Get feedback from summit session.
 +
# Get more feedback from email list + other interested parties.
 +
# Form group of interested folks that would like to help move forward the prototypes design principles & usage in other core projects.
  
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===== How it will be addressed =====
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==== Step 3 ====
  
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==== Task rollback ====
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# Select single first target project to use new ''taskflow'' library.
 +
# Incubate ''taskflow'' library using parts from prototype inside said project.
 +
## Keep other active projects involved from the start (so that said library can be easily used there).
 +
# Prove library in said single first target project by using it to do a key workflow.
 +
## Adjust workflow in chunks in said target project to use said library.
 +
# Adjust tests for each small chunks (depending on what it changes) and add new ones for new functionality.
 +
# Submit chunks into http://review.openstack.org (disabling whole/pieces component until ready to turn on?).
  
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===== Why it matters =====
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==== Step 4 ====
  
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===== How it will be addressed =====
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# Move ''taskflow'' library (and associated tests) into oslo.
  
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==== Task tracking ====
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==== Step 5 ====
  
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===== Why it matters =====
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# Pick another flow and refactor it in said first project ''and/or'' pick another interested project for said flow.
 +
# Split this other flow into small chunks using said library.
 +
# Adjust unit tests for each small chunks (depending on what it changes) and add new ones for new functionality.
 +
# Submit chunks into http://review.openstack.org (disabling whole/pieces component until ready to turn on?).
 +
# Rinse & repeat.
  
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===== How it will be addressed =====
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== Prototype ==
  
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==== Resource locking ====
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https://github.com/Yahoo/NovaOrc
  
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===== Why it matters =====
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=== Design ===
  
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===== How it will be addressed =====
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[[File:New-arch.png|thumbnail|center]]
−
 
 
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==== Workflow sharding/ownership ====
 
−
 
 
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===== Why it matters =====
 
−
 
 
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===== How it will be addressed =====
 
−
 
 
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==== Simplicity ====
 
  
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===== Why it matters =====
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=== Workflow ===
 +
[[File:Run_workflow.png|thumbnail|center]]
  
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===== How it will be addressed =====
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== More  Details! ==
  
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==== Tolerant to upgrades ====
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See: [[StructuredStateManagementDetails]]
  
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===== Why it matters =====
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See: [[StructuredWorkflowPrimitives]]
  
−
===== How it will be addressed =====
+
Get involved: [[StructuredWorkflows]]

Latest revision as of 20:16, 25 May 2013

Drafter: Harlowja

Revised on: 5/25/2013 by Harlowja

Rationale

Move away from ad-hoc states and state transitions for resource acquisition and modification to a more well-defined organized state management system. This new state management system will have advanced new & shiny features such as greater stability, automatic recovery mechanisms and greater scalability than what currently exists (and more!).

Definitions

State
The particular condition that someone or something is in at a specific time: "the state of the instance request".
State transition
Altering a state by applying a function on-top of that state (of which said function may take inputs and provide outputs) resulting in a new state.
Task
The application of a state transition on a given state.
Workflow
The sequence of administrative/other processes through which a piece of work passes from initiation to completion.
State management engine
An individual or entity that arranges or control the elements of, as to achieve a desired overall effect.

What problems is this attempting to solve

  • Increasing the ['extendability', 'recoverability', 'reliability', 'stability'] of states and state transitions.
  • Making it easier to [ 'add', 'debug', 'review', 'test', 'understand', 'verify'] existing & new states and state transitions.
  • Removing hard to discover state & transition dependencies and interactions.
  • Ensuring state transitions are done ['correctly', 'reliably'] by isolating those transitions to a entity whose exclusive responsibility is to ['correctly', 'reliably'] perform said transitions.
  • Fixing a variety of problems that previously had piecemeal like patches applied to solve them.
  • Eliminating the inherent fragility of the current ad-hoc workflows.
  • Allows for upgrading a cloud/software with inflight actions without needing later manual cleanup of said actions.
  • Makes it possible to audit & track the state transitions performed on a given resource in a unified manner.
    • Note: that there currently exists notifications, logging, event reporting as different mechanisms (which are not used in a uniform manner).
  • Removes the need for certain types of periodic tasks which start to consume more and more resources as you grow your cluster larger.
  • Moves toward the path where actions will automatically recover on cutting events (node failure, resource failure, network failure..).
  • Removes the need for periodic tasks to cleanup garbage (orphaned instances/resources/tasks...) left behind.
  • Creates the foundation for a more reliable and automatic recovery process when errors do occur.
  • Encourages the ['altering', 'extension'] of default workflows with a more ['complex', 'custom', 'experimental'] workflows.

Fixing a known need

Blueprints

Related papers

Related wikis

Potential Requirements

https://etherpad.openstack.org/task-system

Summit Discussions

Havana summit:

Plan of record

Step 1

Create prototype

  1. Create core workflow/task library and prototype using said library in nova for run_instance action.
  2. Split this action (refactored) into small atomic task chunks (don't aim for perfection just yet, since its a prototype).
  3. Organize chunks into a workflow and test workflow.
  4. Show working prototype at summit session (with associated docs...)

Step 2

  1. Get feedback on prototype from people involved in making it + other interested parties.
  2. Get feedback from summit session.
  3. Get more feedback from email list + other interested parties.
  4. Form group of interested folks that would like to help move forward the prototypes design principles & usage in other core projects.

Step 3

  1. Select single first target project to use new taskflow library.
  2. Incubate taskflow library using parts from prototype inside said project.
    1. Keep other active projects involved from the start (so that said library can be easily used there).
  3. Prove library in said single first target project by using it to do a key workflow.
    1. Adjust workflow in chunks in said target project to use said library.
  4. Adjust tests for each small chunks (depending on what it changes) and add new ones for new functionality.
  5. Submit chunks into http://review.openstack.org (disabling whole/pieces component until ready to turn on?).

Step 4

  1. Move taskflow library (and associated tests) into oslo.

Step 5

  1. Pick another flow and refactor it in said first project and/or pick another interested project for said flow.
  2. Split this other flow into small chunks using said library.
  3. Adjust unit tests for each small chunks (depending on what it changes) and add new ones for new functionality.
  4. Submit chunks into http://review.openstack.org (disabling whole/pieces component until ready to turn on?).
  5. Rinse & repeat.

Prototype

https://github.com/Yahoo/NovaOrc

Design

New-arch.png

Workflow

Run workflow.png

More Details!

See: StructuredStateManagementDetails

See: StructuredWorkflowPrimitives

Get involved: StructuredWorkflows

Retrieved from "https://wiki.openstack.org/w/index.php?title=StructuredStateManagement&oldid=23471"