1. TOSCA workflows

2. TOSCA workflows
Default workflow is declarative (generated from nodes and relationships)
install
at the beginning of install workflow all instances are in initial state.
at the end of install workflow all planned instances must be in started state
uninstall
at the end of uninstall workflow all instances must be in deleted state
Multiple solutions to allow users customize workflows
Imperative
Full override
Partial override
Declarative improvements
Various solutions are not exclusive

3. Full workflow override
Upsides
Simple from orchestrator perspective
User has a full-vision and understanding of the workflow
No doubt on TOSCA default workflow weaving (dependencies and sequencing between related nodes).
Downsides
Can be fastidious to write without tools
Workflow is specific to a given topology template

4. Full workflow override
Inspired by mistral
Adapted for TOSCA
Simplified declaration
Simplification, no need for inputs and outputs that are already defined on operations and using get_operation_output

5. Full workflow override
Single activity per step
Or allow multiple sequential activities per step ?
topology_template:
workflows:
<workflow_identifier>
description: <workflow_description>
inputs: <parameter_definition_list> # (can be used from operations using get_input as in standard topology template)
steps: # map of steps
<step_name>:
node: <node_name>
requirement: <relationship_name> # name of the requirement/relationship of the node activity: # sequence of activities to be executed in a sequential way
<activity_type>: <activity_configuration>
on-success:
- <list of step names>
topology_template:
workflows:
<workflow_identifier>
description: <workflow_description>
inputs: <parameter_definition_list> # (can be used from operations using get_input as in standard topology template)
steps: # map of steps
<step_name>:
node: <node_name>
requirement: <relationship_name> # name of the requirement/relationship of the node activities: # sequence of activities to be executed in a sequential way
- <activity_type>: <activity_configuration>
on-success:
- <list of step names>

6. Full workflow override
Activity type
description
delegate
Activity to be used when a node is not provided by a user but should be provided by the orchestrator engine (Compute, BlockStorage etc.). For such node weaving operations of relationships that are not also provided by the orchestrator should be prohibited.
set_state
Change the state of a node to a given state.
call_operation
Call the operation of the specified node (or one of it’s relationship). Inputs of the operation are defined on the operation element.
Delegate activity is important for portability in some use-cases
Orchestrator to provide nodes (Compute, BlockStorage etc.) where implementation can be specific
Reusability of existing services (an existing Oracle DB on the cloud to be matched against an abstract DB node in the topology one one cloud vs. creating one on the fly on another cloud)

7. Full workflow override
The on-success values are used to build the workflow graph. All steps that have a on-success defined to a given step should be executed before it (join).
All steps that doesn’t have a predecessor are considered as initial step and can run in parallel.
All steps that doesn’t have a successor are considered as final.
The TOSCA parser/validator SHOULD ensure that
all nodes MUST reach the started state at the end of the install workflow
all nodes MUST reach the deleted state at the end of the uninstall workflow

8. Full workflow override
steps: A:
on-success:
- B
- C B:
- D C: D: E:
- F F: A E B C F D

9. Sample:
The workflow that creates the compute node until started state is delegated to the orchestrator
compute started
tomcat
Tomcat
Requirements
Host
mysql creating
tomcat creating
mysql create
tomcat create
mysql created
tomcat created
HostedOn
mysql
MySQL
Requirements
Host
mysql starting
mysql start
mysql started
HostedOn
compute
tosca.nodes.Compute
Capabilities
Container
This scenario aims to
allow to perform tomcat’s creation in parallel of mysql creation and start (bypass the single concurrent operation per compute constraint)
Start tomcat after mysql even if no relation is specified between the two nodes
Tomcat starting
tomcat start
Tomcat started

10. Sample Delegating can be a mapping.
topology_template:
workflows:
install:
description: Workflow to deploy the application
steps:
Compute_install:
target: Compute
activities:
- delegate: install
on-success:
- Mysql_initial
- Tomcat_initial
Tomcat_initial:
target: Tomcat
- set_state: creating
- call_operation: tosca.interfaces.node.lifecycle.Standard.create
- set_state: created
- Tomcat_starting
Mysql_initial:
node: Mysql
- set_state: starting
- call_operation: tosca.interfaces.node.lifecycle.Standard.start
- set_state: started
Sample
Tomcat_starting:
target: Tomcat
activities:
- set_state: starting
- call_operation: tosca.interfaces.node.lifecycle.Standard.start
- set_state: started
on-success:
- Tomcat_starting
Delegating can be a mapping.
Think about convention for sure naming

11. Partial workflow override
Work in progress
Upsides
Easier to write if a user has no tool
Downsides
May be prone to errors as it may be harder to understand what will be added or not by the TOSCA orchestrator (no automatic weaving should be done between steps that are defined in an implicit workflow).
Only for install and uninstall workflows ?
Custom workflows and other scenarios will anyway probably require a full-workflow describtion
Workflow is specific to a given topology template

12. Partial workflow override
Work in progress
Similar to full workflow override but you can have more than one partial workflow.
Partial workflow let the orchestrator generate the workflow of nodes before the
topology_template:
workflows:
<workflow_identifier>
description: <workflow_description>
inputs: <parameter_definition_list> # (can be used from operations using get_input as in standard topology template)
partials:
steps: # map of steps for the partial workflow
<step_name>:
node: <node_name>
requirement: <relationship_name> # name of the requirement/relationship of the node activities: # sequence of activities to be executed in a sequential way
- <activity_type>: <activity_configuration>
on-success:
- <list of step names>

13. Declarative workflows improvements (TOSCA-219)
Upsides
Can onboard ‘workflow updates’ on types and make them reusable (not specific to a topology template)
Downsides
Less focused on reusability on a specific existing workflow for a specific topology (need to get into TOSCA declarative workflow logic)

14. Declarative workflows improvements
Add elements to instruct the declarative workflows for types
Node Types
Relationships Types
Allow to override them on templates (like interfaces)

15. Declarative workflows improvements
Work in progress
node_types:
<node_type>:
workflows: # Defines the workflow for the given node.
<workflow_identifier>:
steps: # map of steps (you can even do some things in parallel for a single node if that make sense)
<step_name>:
activities: # sequence of activities to be executed in a sequential way
- <activity_type>: <activity_configuration>
on-success:
- <list of step names>

16. Declarative workflows improvements
Work in progress
node_types:
tosca.nodes.Root:
workflows:
install:
steps:
install_sequence:
activities:
- set_state: creating
- call_operation: tosca.interfaces.node.lifecycle.Standard.create
- set_state: created
- set_state: configuring
- call_operation: tosca.interfaces.node.lifecycle.Standard.configure
- set_state: configured
- set_state: starting
- call_operation: tosca.interfaces.node.lifecycle.Standard.start
- set_state: started
uninstall:
uninstall_sequence:
- set_state: stopping
- call_operation: tosca.interfaces.node.lifecycle.Standard.stop
- set_state: stopped
- set_state: deleting
- call_operation: tosca.interfaces.node.lifecycle.Standard.delete
- set_state: deleted
Group and clusters
- Mongo
Scalable single nodes
- Zookeeper

17. Declarative workflows improvements
Work in progress
relationship_types:
tosca.relationships.ConnectsTo:
workflow:
install: # name of the workflow for wich the weaving has to be taken in account
source_weaving: # Instruct how to weave some tasks on the source workflow (executed on SOURCE instance)
- after: configuring # instruct that this operation should be weaved after the target reach configuring state
wait_target: created # add a join from a state of the target
activity: tosca.interfaces.relationships.Configure.pre_configure_source
- before: configured # instruct that this operation should be weaved before the target reach configured state
activity: tosca.interfaces.relationships.Configure.post_configure_source
- before: starting
wait_target: started # add a join from a state of the target
- after: started
activity: tosca.interfaces.relationships.Configure.add_target
target_weaving: # Instruct how to weave some tasks on the target workflow (executed on TARGET instance)
after_source: created # add a join from a state of the source
activity: tosca.interfaces.relationships.Configure.pre_configure_target
activity: tosca.interfaces.relationships.Configure.post_configure_target
activity: tosca.interfaces.relationships.Configure.add_source

18. Declarative workflows improvements
TODO:
Provide elements relative to instance model
Scaled Apache node: each node has independent workflow
Scaled Zookeeper node: Ideally I would like to wait that all zookeeper instances are created before I do the configure operations
Manage impacts and weaving of Groups interfaces for some clusters scenarios