cadence-client 0.0.2

Python framework for Cadence Workflow Service

Python framework for Cadence Workflow Service

Cadence is a workflow engine developed at Uber Engineering. With this framework, workflows and activities managed by Cadence can be implemented in Python code.

Status / TODO

cadence-python is still under going heavy development. It should be considered EXPERIMENTAL at the moment. A production version is targeted to be released in September of 2019 January 2020.

• Tchannel implementation
• Python-friendly wrapper around Cadence's Thrift API
• Author activities in Python
• Start workflows (synchronously)
• Create workflows
• Workflow execution in coroutines
• Invoke activities from workflows
• Activity heartbeating and doNotCompleteOnReturn
• Activity retry
• Signals
• Queries
• Async workflow execution
• await
• now (currentTimeMillis)
• Timers
• Sleep
• Loggers
• newRandom
• UUID
• Workflow Versioning

2.0

• Sticky workflows

Post 2.0:

• sideEffect/mutableSideEffect
• Parallel activity execution
• Cancellation Scopes
• Child Workflows

Installation

pip install cadence-client

Hello World Sample

import sys
import logging
from cadence.activity_method import activity_method
from cadence.workerfactory import WorkerFactory
from cadence.workflow import workflow_method, Workflow, WorkflowClient

logging.basicConfig(level=logging.DEBUG)

TASK_LIST = "HelloActivity-python-tasklist"
DOMAIN = "sample"


# Activities Interface
class GreetingActivities:
    @activity_method(task_list=TASK_LIST, schedule_to_close_timeout_seconds=2)
    def compose_greeting(self, greeting: str, name: str) -> str:
        raise NotImplementedError


# Activities Implementation
class GreetingActivitiesImpl:
    def compose_greeting(self, greeting: str, name: str):
        return greeting + " " + name + "!"


# Workflow Interface
class GreetingWorkflow:
    @workflow_method(execution_start_to_close_timeout_seconds=10, task_list=TASK_LIST)
    async def get_greeting(self, name: str) -> str:
        raise NotImplementedError


# Workflow Implementation
class GreetingWorkflowImpl(GreetingWorkflow):

    def __init__(self):
        self.greeting_activities: GreetingActivities = Workflow.new_activity_stub(GreetingActivities)

    async def get_greeting(self, name):
        return await self.greeting_activities.compose_greeting("Hello", name)


if __name__ == '__main__':
    factory = WorkerFactory("localhost", 7933, DOMAIN)
    worker = factory.new_worker(TASK_LIST)
    worker.register_activities_implementation(GreetingActivitiesImpl(), "GreetingActivities")
    worker.register_workflow_implementation_type(GreetingWorkflowImpl)
    factory.start()

    client = WorkflowClient.new_client(domain=DOMAIN)
    greeting_workflow: GreetingWorkflow = client.new_workflow_stub(GreetingWorkflow)
    result = greeting_workflow.get_greeting("Python")
    print(result)

    print("Stopping workers....")
    worker.stop()
    print("Workers stopped...")
    sys.exit(0)