Difference between revisions of "StructuredStateManagement"
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== More Details! == | == More Details! == | ||
See: [[StructuredWorkflowPrimitives]] | See: [[StructuredWorkflowPrimitives]] | ||
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See: [[StructuredStateManagementDetails]] | See: [[StructuredStateManagementDetails]] | ||
See: [[StructuredWorkflows]] | See: [[StructuredWorkflows]] |
Revision as of 20:01, 25 May 2013
Please note that this is a PROPOSAL ONLY. This is not yet 100% implemented.
Drafter: Harlowja
Contents
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
- 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
- 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
- https://bugs.launchpad.net/nova/+bug/1173430
- (and more)
Blueprints
- https://blueprints.launchpad.net/nova/+spec/structured-state-management
- https://blueprints.launchpad.net/cinder/+spec/cinder-state-machine
Related papers
- http://www.netdb.cis.upenn.edu/papers/tropic_tr.pdf
- http://research.microsoft.com/pubs/64604/osr2007.pdf
Related wikis
- https://wiki.openstack.org/wiki/Convection
- https://wiki.openstack.org/wiki/NovaOrchestration/WorkflowEngines (old)
Potential Requirements
https://etherpad.openstack.org/task-system
Summit Discussions
Havana summit:
- https://etherpad.openstack.org/the-future-of-orch
- https://etherpad.openstack.org/Summit-Havana-Cinder-Safe-Shutdown
Plan of record
Step 1
Create prototype
- 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...)
Step 2
- 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.
Step 3
- 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?).
Step 4
- Move taskflow library (and associated tests) into oslo.
Step 5
- 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.
Prototype
https://github.com/Yahoo/NovaOrc
Design
Workflow
More Details!
See: StructuredWorkflowPrimitives
See: StructuredStateManagementDetails
See: StructuredWorkflows