StackStorm介紹

StackStorm是一個強大的自動化平臺，結合DevOps和ChatOps，提供可擴展、靈活和健壯的工具鏈用於應用、服務和工作流的自動化能力。

Mistral

Mistral是Mirantis公司爲Openstack開發的工作流組件，提供Workflow as aService。Stackstorm集成了Mistral，提供更加靈活和強大的Workflow支持。

Mistral的一些概念，需要和StackStrom的概念區分開來：

Workbook：工作簿。可以理解爲工作流任務的文檔，紀錄了工作流，任務以及任務的執行順序，依賴關係，以及每個任務的輸入輸出等。從開發者的角度看，可以認爲它是一種工作流任務的文檔組織形式，或者命名空間。
Workflow：工作流。比Workbook小的單元。描述了任務，動作的執行順序，依賴關係。一個Workbook可以有多條Workflow，也可以只有一條Workflow。
Task:描述Workflow中包含的工作步驟。
Action:Mistral中最小的單位，描述了某一個具體的動作，比如執行一個http請求，或者發一個e-mail等等。

YAQL & Jinja

Mistral中支持的模板解析語法有YAQL和Jinja，這提供了強大的流程控制和語法支持。下面對比下YAQL和Jinja:

YAQL:

version: '2.0'

examples.mistral-branching:

description: >

A sample workflow that demonstrates how to use conditions

to determine which path in the workflow to take.

type: direct

input:

- which

tasks:

t1:

action: core.local

input:

cmd: "printf <% $.which %>"

publish:

path: <% task(t1).result.stdout %>

on-success:

- a: <% $.path = 'a' %>

- b: <% $.path = 'b' %>

- c: <% not $.path in list(a, b) %>

action: core.local

input:

cmd: "echo 'Took path A.'"

publish:

stdout: <% task(a).result.stdout %>

action: core.local

input:

cmd: "echo 'Took path B.'"

publish:

stdout: <% task(b).result.stdout %>

action: core.local

input:

cmd: "echo 'Took path C.'"

publish:

stdout: <% task(c).result.stdout %>

Jinja

version: '2.0'

examples.mistral-jinja-branching:

description: >

A sample workflow that demonstrates how to use conditions

to determine which path in the workflow to take.

type: direct

input:

- which

tasks:

t1:

action: core.local

input:

cmd: "echo {{ _.which }}"

publish:

path: "{{ task('t1').result.stdout }}"

on-success:

- a: "{{ _.path == 'a' }}"

- b: "{{ _.path == 'b' }}"

- c: "{{ not _.path in ['a', 'b'] }}"

action: core.local

input:

cmd: "echo 'Took path A.'"

action: core.local

input:

cmd: "echo 'Took path B.'"

action: core.local

input:

cmd: "echo 'Took path C.'"

Mistral示例

StackStorm的examples下面提供了關於Mistral的示例，我們接下來通過一系列的示例來說明Mistral。

examples.mistral-basic

同樣的MistralWorkflow跟ActionChainWorkflow一樣都需要提供元數據文件和規格文件，

Pack examples的元數據文件是在/opt/stackstorm/packs/examples/actions目錄下，規格文件是在/opt/stackstorm/packs/examples/actions/workflows目錄下.

/opt/stackstorm/packs/examples/actions/mistral-basic.yaml

---

description: Run a local linux command

enabled: true

runner_type: mistral-v2

entry_point: workflows/mistral-basic.yaml

pack: examples

parameters:

cmd:

required: true

type: string

timeout:

type: integer

default: 60

規格文件/opt/stackstorm/packs/examples/actions/workflows/mistral-basic.yaml

version: '2.0'

examples.mistral-basic:

description: A basic workflow that runs an arbitrary linux command.

type: direct

input:

- cmd

- timeout

output:

stdout: <% $.stdout %>

tasks:

task1:

action: core.local cmd=<% $.cmd %> timeout=<% $.timeout %>

publish:

stdout: <% task(task1).result.stdout %>

stderr: <% task(task1).result.stderr %>

根據定義examples.mistral-basic需要提供參數cmd（必選）和timeout（可選），然後在task1中調用core.local執行，並且打印執行結果。執行如下：

$ st2 run examples.mistral-basic cmd="date"

id: 5afba6ed2b2556015687cdda

action.ref: examples.mistral-basic

parameters:

cmd: date

status: succeeded

result_task: task1

result:

failed: false

return_code: 0

stderr: ''

stdout: Wed May 16 03:35:10 UTC 2018

succeeded: true

start_timestamp: Wed, 16 May 2018 03:35:09 UTC

end_timestamp: Wed, 16 May 2018 03:35:11 UTC

+--------------------------+------------------------+-------+------------+-------------------------------+

+--------------------------+------------------------+-------+------------+-------------------------------+

+--------------------------+------------------------+-------+------------+-------------------------------+

examples. mistral-workbook-basic

Mistral中有個WorkBook的概念，是Workflow的組合，也就是說可以同時定義多個Workflow

/opt/stackstorm/packs/examples/actions/workflows/mistral-workbook-multiple-subflows.yaml

version: "2.0"

workflows:

main:

type: direct

output:

report: <% $.report %>

state: <% $.state %>

tasks:

call_internal_workflow:

workflow: wf1

input:

v1: ok

publish:

report: <% task(call_internal_workflow).result.report %>

on-success:

- call_internal_workflow_multiple_tasks

call_internal_workflow_multiple_tasks:

workflow: wf2

input:

v1: good

v2: excellent

on-success:

- call_external_workflow

call_external_workflow:

action: examples.mistral-basic

input:

cmd: "echo 'external workflow ok'"

publish:

state: <% task(call_external_workflow).result.stdout %>

on-success:

- call_action_chain

call_action_chain:

action: examples.echochain

wf1:

type: direct

input:

- v1

output:

report: <% $.report %>

tasks:

t1:

action: core.local

input:

cmd: "echo 'task1 <% $.v1 %>'; sleep 1"

publish:

report: <% task(t1).result.stdout %>

wf2:

type: direct

input:

- v1

- v2

tasks:

t1:

action: core.local

input:

cmd: "echo 'task2 <% $.v1 %>'; sleep 1"

t2:

action: core.local

input:

cmd: "echo 'task3 <% $.v2 %>'; sleep 2"

examples.mistral-handle-error

Mistral Workflow通過可以設置子任務成功失敗後的執行順序，

/opt/stackstorm/packs/examples/actions/workflows/mistral-handle-error.yaml：

version: '2.0'

examples.mistral-handle-error:

description: >

A workflow example that illustrates error handling. By default when any task fails,

the notify_on_error task will be executed and the workflow will transition to the

failed state.

type: direct

input:

- cmd

vars:

error_handled: False

tasks:

task1:

action: core.local cmd="echo 1 && exit 0"

publish:

stdout: <% task(task1).result.stdout %>

on-success:

- task2

on-error:

- handle_error

task2:

action: core.local cmd="echo 2 && exit 1"

publish:

stdout: <% task(task1).result.stdout %>

on-error:

- handle_error

handle_error:

action: core.local

input:

cmd: "printf '<% task(task1).result.stderr %>'"

publish:

error_handled: True

on-complete:

- fail

examples.mistral-handle-error定義了task1和task2，task1成功後執行task2，task2失敗後執行handle_error。

$ st2 run examples.mistral-handle-error

id: 5afbca362b2556015687cddf

action.ref: examples.mistral-handle-error

parameters: None

status: failed

start_timestamp: Wed, 16 May 2018 06:05:42 UTC

end_timestamp: Wed, 16 May 2018 06:05:45 UTC

+--------------------------+------------------------+--------------+------------+-------------------------------+

+--------------------------+------------------------+--------------+------------+-------------------------------+

Mistral Workflow可以針對失敗的子任務進行重跑（StackStorm2.7版本的ActionChain不支持從失敗的子任務繼續重跑）：

$ st2 execution re-run 5afbca362b2556015687cddf --tasks task2

id: 5afbcadc2b2556015687cde8

action.ref: examples.mistral-handle-error

parameters: None

status: failed

result_task: task2

result:

failed: true

return_code: 1

stderr: ''

stdout: 2

succeeded: false

start_timestamp: Wed, 16 May 2018 06:08:28 UTC

end_timestamp: Wed, 16 May 2018 06:08:30 UTC

+--------------------------+------------------------+--------------+------------+-------------------------------+

+--------------------------+------------------------+--------------+------------+-------------------------------+

+--------------------------+------------------------+--------------+------------+-------------------------------+

examples.mistral-repeat

Mistral Workflow支持循環語法：

/opt/stackstorm/packs/examples/actions/workflows/mistral-repeat.yaml

version: '2.0'

examples.mistral-repeat:

description: >

A sample workflow that demonstrates how to repeat a task

x number of times with the same inputs.

type: direct

input:

- cmd

- count

tasks:

repeat:

with-items: i in <% list(range(0, $.count)) %>

action: core.local cmd=<% $.cmd %>

publish:

result: <% task(repeat).result.select($.stdout) %>

循環5次執行命令：

st2 run examples.mistral-repeat cmd=date count=5

id: 5afbdab82b2556015687ce19

action.ref: examples.mistral-repeat

parameters:

cmd: date

status: succeeded

result_task: repeat

result: - failed: false

return_code: 0

stderr: ''