c3d3138516
* A lot of redundant info has been cleanup * Deleted the docker install guide (was obsolete) * Move mistral client from admin to user guide * Various cleanup in doc Change-Id: I5c0c27653a053603bb6ad8428db18024a58533a8 Signed-off-by: Arnaud M <arnaud.morin@gmail.com>
141 lines
4.9 KiB
ReStructuredText
141 lines
4.9 KiB
ReStructuredText
Workflows
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=========
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Workflow is the main building block of Mistral Workflow Language, the reason
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why the project exists. Workflow represents a process that can be described in
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a various number of ways and that can do some job interesting to the end user.
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Each workflow consists of tasks (at least one) describing what exact steps
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should be made during workflow execution.
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YAML example
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^^^^^^^^^^^^
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::
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---
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version: '2.0'
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create_vm:
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description: Simple workflow sample
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type: direct
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input: # Input parameter declarations
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- vm_name
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- image_ref
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- flavor_ref
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output: # Output definition
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vm_id: <% $.vm_id %>
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tasks:
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create_server:
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action: nova.servers_create name=<% $.vm_name %> image=<% $.image_ref %> flavor=<% $.flavor_ref %>
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publish:
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vm_id: <% task().result.id %>
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on-success:
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- wait_for_instance
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wait_for_instance:
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action: nova.servers_find id=<% $.vm_id %> status='ACTIVE'
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retry:
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delay: 5
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count: 15
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Workflow types
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^^^^^^^^^^^^^^
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Mistral Workflow Language v2 introduces different workflow types and the
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structure of each workflow type varies according to its semantics. Currently,
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Mistral provides two workflow types:
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- `Direct workflow <#direct-workflow>`__
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- `Reverse workflow <#reverse-workflow>`__
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See corresponding sections for details.
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Direct workflow
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^^^^^^^^^^^^^^^
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Direct workflow consists of tasks combined in a graph where every next
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task starts after another one depending on produced result. So direct
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workflow has a notion of transition. Direct workflow is considered to be
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completed if there aren't any transitions left that could be used to
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jump to next tasks.
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.. image:: img/direct_workflow.png
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YAML example of direct workflow
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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::
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---
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version: '2.0'
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create_vm_and_send_email:
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type: direct
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input:
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- vm_name
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- image_id
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- flavor_id
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output:
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result: <% $.vm_id %>
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tasks:
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create_vm:
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action: nova.servers_create name=<% $.vm_name %> image=<% $.image_id %> flavor=<% $.flavor_id %>
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publish:
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vm_id: <% task().result.id %>
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on-error:
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- send_error_email
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on-success:
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- send_success_email
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send_error_email:
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action: send_email to='admin@mysite.org' body='Failed to create a VM'
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on-complete:
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- fail
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send_success_email:
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action: send_email to='admin@mysite.org' body='Vm is successfully created and its id is <% $.vm_id %>'
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Reverse workflow
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^^^^^^^^^^^^^^^^
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In reverse workflow all relationships in workflow task graph are
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dependencies. In order to run this type of workflow we need to specify a
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task that needs to be completed, it can be conventionally called 'target
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task'. When Mistral Engine starts a workflow it recursively identifies
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all the dependencies that need to be completed first.
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.. image:: img/reverse_workflow.png
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The figure explains how reverse workflow works. In the example, task
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**T1** is chosen a target task. So when the workflow starts Mistral will
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run only tasks **T7**, **T8**, **T5**, **T6**, **T2** and **T1** in the
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specified order (starting from tasks that have no dependencies). Tasks
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**T3** and **T4** won't be a part of this workflow because there's no
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route in the directed graph from **T1** to **T3** or **T4**.
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YAML example of reverse workflow
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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::
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---
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version: '2.0'
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create_vm_and_send_email:
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type: reverse
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input:
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- vm_name
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- image_id
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- flavor_id
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output:
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result: <% $.vm_id %>
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tasks:
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create_vm:
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action: nova.servers_create name=<% $.vm_name %> image=<% $.image_id %> flavor=<% $.flavor_id %>
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publish:
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vm_id: <% task().result.id %>
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search_for_ip:
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action: nova.floating_ips_findall instance_id=null
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publish:
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vm_ip: <% task().result[0].ip %>
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associate_ip:
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action: nova.servers_add_floating_ip server=<% $.vm_id %> address=<% $.vm_ip %>
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requires: [search_for_ip]
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send_email:
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action: send_email to='admin@mysite.org' body='Vm is created and id <% $.vm_id %> and ip address <% $.vm_ip %>'
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requires: [create_vm, associate_ip]
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For more details about Mistral Workflow Language itself, please see
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:doc:`Mistral Workflow Language specification </user/wf_lang_v2>`
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