使用Python开源库Couler编写和提交Argo Workflow工作流

Python 是用户在 Kubernetes 上编写机器学习工作流的流行编程语言。

开箱即用时，Argo 并没有为 Python 提供一流的支持。相反，我们提供Java、Golang 和 Python API 客户端[1]。

但这对大多数用户来说还不够。许多用户需要一个抽象层来添加组件和特定于用例的特性。

今天你有两个选择。

KFP 编译器+ Python 客户端

Argo 工作流被用作执行 Kubeflow 流水线的引擎。你可以定义一个 Kubeflow 流水线，并在 Python 中将其直接编译到 Argo 工作流中。

然后你可以使用Argo Python 客户端[2]向 Argo 服务器 API 提交工作流。

这种方法允许你利用现有的 Kubeflow 组件。

安装：

pip3 install kfp
pip3 install argo-workflows

例子：

import kfp as kfp
def flip_coin():
    return kfp.dsl.ContainerOp(
        name='Flip a coin',
        image='python:alpine3.6',
        command=['python', '-c', """
import random
res = "heads" if random.randint(0, 1) == 0 else "tails"
with open('/output', 'w') as f:
    f.write(res)
        """],
        file_outputs={'output': '/output'}
    )
def heads():
    return kfp.dsl.ContainerOp(name='Heads', image="alpine:3.6", command=["sh", "-c", 'echo "it was heads"'])
def tails():
    return kfp.dsl.ContainerOp(name='Tails', image="alpine:3.6", command=["sh", "-c", 'echo "it was tails"'])
@kfp.dsl.pipeline(name='Coin-flip', description='Flip a coin')
def coin_flip_pipeline():
    flip = flip_coin()
    with kfp.dsl.Condition(flip.output == 'heads'):
        heads()
    with kfp.dsl.Condition(flip.output == 'tails'):
        tails()
def main():
    kfp.compiler.Compiler().compile(coin_flip_pipeline, __file__ + ".yaml")
if __name__ == '__main__':
    main()

运行这个来创建你的工作流：

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: coin-flip-
  annotations: {pipelines.kubeflow.org/kfp_sdk_version: 1.3.0, pipelines.kubeflow.org/pipeline_compilation_time: '2021-01-21T17:17:54.299235',
    pipelines.kubeflow.org/pipeline_spec: '{"description": "Flip a coin", "name":
      "Coin-flip"}'}
  labels: {pipelines.kubeflow.org/kfp_sdk_version: 1.3.0}
spec:
  entrypoint: coin-flip
  templates:
  - name: coin-flip
    dag:
      tasks:
      - name: condition-1
        template: condition-1
        when: '"{{tasks.flip-a-coin.outputs.parameters.flip-a-coin-output}}" == "heads"'
        dependencies: [flip-a-coin]
      - name: condition-2
        template: condition-2
        when: '"{{tasks.flip-a-coin.outputs.parameters.flip-a-coin-output}}" == "tails"'
        dependencies: [flip-a-coin]
      - {name: flip-a-coin, template: flip-a-coin}
  - name: condition-1
    dag:
      tasks:
      - {name: heads, template: heads}
  - name: condition-2
    dag:
      tasks:
      - {name: tails, template: tails}
  - name: flip-a-coin
    container:
      command:
      - python
      - -c
      - "\nimport random\nres = \"heads\" if random.randint(0, 1) == 0 else \"tails\"\
        \nwith open('/output', 'w') as f:\n    f.write(res)        \n        "
      image: python:alpine3.6
    outputs:
      parameters:
      - name: flip-a-coin-output
        valueFrom: {path: /output}
      artifacts:
      - {name: flip-a-coin-output, path: /output}
  - name: heads
    container:
      command: [sh, -c, echo "it was heads"]
      image: alpine:3.6
  - name: tails
    container:
      command: [sh, -c, echo "it was tails"]
      image: alpine:3.6
  arguments:
    parameters: []
  serviceAccountName: pipeline-runner

注意，Kubeflow 不支持这种方法。

你可以使用客户端提交上述工作流程如下：

import yaml
from argo.workflows.client import (ApiClient,
                                   WorkflowServiceApi,
                                   Configuration,
                                   V1alpha1WorkflowCreateRequest)
def main():
    config = Configuration(host="http://localhost:2746")
    client = ApiClient(configuration=config)
    service = WorkflowServiceApi(api_client=client)
with open("coin-flip.py.yaml") as f:
        manifest: dict = yaml.safe_load(f)
del manifest['spec']['serviceAccountName']
service.create_workflow('argo', V1alpha1WorkflowCreateRequest(workflow=manifest))
if __name__ == '__main__':
    main()

Couler

Couler[3]是一个流行的项目，它允许你以一种平台无感的方式指定工作流，但它主要支持 Argo 工作流（计划在未来支持 Kubeflow 和 AirFlow）：

安装：

pip3 install git+https://github.com/couler-proj/couler

例子：

import couler.argo as couler
from couler.argo_submitter import ArgoSubmitter
def random_code():
    import random
res = "heads" if random.randint(0, 1) == 0 else "tails"
    print(res)
def flip_coin():
    return couler.run_script(image="python:alpine3.6", source=random_code)
def heads():
    return couler.run_container(
        image="alpine:3.6", command=["sh", "-c", 'echo "it was heads"']
    )
def tails():
    return couler.run_container(
        image="alpine:3.6", command=["sh", "-c", 'echo "it was tails"']
    )
result = flip_coin()
couler.when(couler.equal(result, "heads"), lambda: heads())
couler.when(couler.equal(result, "tails"), lambda: tails())
submitter = ArgoSubmitter()
couler.run(submitter=submitter)

这会创建以下工作流程：

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: couler-example-
spec:
  templates:
    - name: couler-example
      steps:
        - - name: flip-coin-29
            template: flip-coin
        - - name: heads-31
            template: heads
            when: '{{steps.flip-coin-29.outputs.result}} == heads'
          - name: tails-32
            template: tails
            when: '{{steps.flip-coin-29.outputs.result}} == tails'
    - name: flip-coin
      script:
        name: ''
        image: 'python:alpine3.6'
        command:
          - python
        source: |
import random
res = "heads" if random.randint(0, 1) == 0 else "tails"
          print(res)
    - name: heads
      container:
        image: 'alpine:3.6'
        command:
          - sh
          - '-c'
          - echo "it was heads"
    - name: tails
      container:
        image: 'alpine:3.6'
        command:
          - sh
          - '-c'
          - echo "it was tails"
  entrypoint: couler-example
  ttlStrategy:
    secondsAfterCompletion: 600
  activeDeadlineSeconds: 300

---

参考资料

使用Python编写和提交Argo工作流 - SegmentFault 思否10人将获赠CNCF商店$100美元礼券！你填了吗？问卷链接（[链接]）作者：Alex CollinsPython 是用户在 Kubernetes 上编写机器学习工作流的流行编程语言。开箱即...https://segmentfault.com/a/1190000039101534[1]

Java、Golang和Python API客户端: https://github.com/argoproj-labs/argo-client-gen

[2]

Argo Python客户端: https://github.com/argoproj-labs/argo-client-python

[3]

Couler: https://github.com/couler-proj/couler