From f0f1eb1c51602f4e69c72040425f1dfa549fb480 Mon Sep 17 00:00:00 2001 From: RizaFarheen Date: Wed, 14 Feb 2024 16:30:55 +0400 Subject: [PATCH] Update python.md --- docs/sdks/python.md | 639 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 632 insertions(+), 7 deletions(-) diff --git a/docs/sdks/python.md b/docs/sdks/python.md index 394e3b91..770aa163 100644 --- a/docs/sdks/python.md +++ b/docs/sdks/python.md @@ -166,14 +166,639 @@ That's it - you just created your first distributed python app! There are three main ways you will use Conductor when building durable, resilient, distributed applications. -1. Write service workers that implements business logic to accomplish a specific goal - such as initiate payment transfer, get user information from database etc. -2. Create Conductor workflows that implements application state - A typical workflow implements Saga pattern +1. Write service workers that implement business logic to accomplish a specific goal - such as initiating payment transfer, getting user information from the database, etc. +2. Create Conductor workflows that implement application state - A typical workflow implements a Saga pattern. 3. Use Conductor SDK and APIs to manage workflows from your application. -- [Create and Run Conductor Workflows](https://github.com/conductor-sdk/conductor-python/blob/main/workers.md) -- [Create Conductor Workflows](https://github.com/conductor-sdk/conductor-python/blob/main/workflows.md) -- [Using Conductor in your Application](https://github.com/conductor-sdk/conductor-python/blob/main/conductor_apps.md) +## Create and Run Conductor Workers -## Related Topics +### Writing Workers -- Video Guide on [Getting Access Key and Secret](/content/how-to-videos/access-key-and-secret) \ No newline at end of file +A workflow task represents a unit of business logic that achieves a specific goal, such as checking inventory, initiating payment transfers, etc. Worker implements a task in the workflow. (note: often times, worker and task are used interchangeably in various blogs, docs, etc.) + +### Implementing Workers + +The workers can be implemented by writing a simple python function and annotating the function with the **@worker_task**. Conductor workers are services (similar to microservices) that follow the [Single Responsibility Principle](https://en.wikipedia.org/wiki/Single_responsibility_principle). + +Workers can be hosted along with the workflow or run in a distributed environment where a single workflow uses workers that are deployed and running in different machines/VMS/containers. Keeping all the workers in the same application or running them as a distributed application is a design and architectural choice. Conductor is well suited for both kind of scenarios. + +You create or convert any existing python function to a distributed worker by adding **@worker_task** annotation to it. Here is a simple worker that takes **name** as input and returns greetings: + +```python +from conductor.client.worker.worker_task import worker_task + +@worker_task(task_definition_name='greetings') +def greetings(name: str) -> str: + return f'Hello, {name}' +``` + +A worker can take inputs that are primitives - **str**, **int**, **float**, **bool**, etc. or can be complex data classes. + +Here is an example worker that uses **dataclass** as part of the worker input. + +```python +from conductor.client.worker.worker_task import worker_task +from dataclasses import dataclass + +@dataclass +class OrderInfo: + order_id: int + sku: str + quantity: int + sku_price: float + + +@worker_task(task_definition_name='process_order') +def process_order(order_info: OrderInfo) -> str: + return f'order: {order_info.order_id}' +``` + +### Managing workers in your application + +Workers use a polling mechanism (with long-poll) to check for any available tasks from server periodically. The startup and shutdown of workers are handled by **conductor.client.automator.task_handler.TaskHandler** class. + +```python +from conductor.client.automator.task_handler import TaskHandler +from conductor.client.configuration.configuration import Configuration + +def main(): + # points to http://localhost:8080/api by default + api_config = Configuration() + + task_handler = TaskHandler( + workers=[], + configuration=api_config, + scan_for_annotated_workers=True, + import_modules=['greetings'] # import workers from this module - leave empty if all the workers are in the same module + ) + + # start worker polling + task_handler.start_processes() + + # Call to stop the workers when the application is ready to shutdown + task_handler.stop_processes() + + +if __name__ == '__main__': + main() +``` + +### Design Principles for Workers + +Each worker embodies the design pattern and follows certain basic principles: + +1. Workers are stateless and do not implement a workflow-specific logic. +2. Each worker executes a very specific task and produces well-defined output given specific inputs. +3. Workers are meant to be idempotent (or should handle cases where the task that is partially executed gets rescheduled due to timeouts, etc.) +4. Workers do not implement the logic to handle retries, etc., that the Conductor server takes care of. + +### System Task Workers + +A system task worker is a pre-built, general-purpose worker in your Conductor server distribution. + +System tasks automate repeated tasks such as calling an HTTP endpoint, executing lightweight ECMA-compliant javascript code, publishing to an event broker, etc. + +#### Wait Task + +:::tip +Wait is a powerful way to have your system wait for a certain trigger, such as an external event, a certain date/time, or a duration, such as 2 hours, without having to manage threads, background processes, or jobs. +::: + +##### Using code to create WAIT task + +```python +from conductor.client.workflow.task.wait_task import WaitTask + +# waits for 2 seconds before scheduling the next task +wait_for_two_sec = WaitTask(task_ref_name='wait_for_2_sec', wait_for_seconds=2) + +# wait until end of jan +wait_till_jan = WaitTask(task_ref_name='wait_till_jsn', wait_until='2024-01-31 00:00 UTC') + +# waits until an API call or an event is triggered +wait_for_signal = WaitTask(task_ref_name='wait_till_jan_end') +``` + +##### JSON configuration + +```json +{ + "name": "wait", + "taskReferenceName": "wait_till_jan_end", + "type": "WAIT", + "inputParameters": { + "until": "2024-01-31 00:00 UTC" + } +} +``` + +#### HTTP Task + +Make a request to an HTTP(S) endpoint. The task allows making GET, PUT, POST, DELETE, HEAD, and PATCH requests. + +##### Using code to create an HTTP task + +```python +from conductor.client.workflow.task.http_task import HttpTask + +HttpTask(task_ref_name='call_remote_api', http_input={ + 'uri': 'https://orkes-api-tester.orkesconductor.com/api' + }) +``` + +##### JSON configuration + +```json +{ + "name": "http_task", + "taskReferenceName": "http_task_ref", + "type" : "HTTP", + "uri": "https://orkes-api-tester.orkesconductor.com/api", + "method": "GET" +} +``` + +#### Javascript Executor Task + +Execute ECMA-compliant Javascript code. It is useful when you need to write a script for data mapping, calculations, etc. + +```python +from conductor.client.workflow.task.javascript_task import JavascriptTask + +say_hello_js = """ +function greetings() { + return { + "text": "hello " + $.name + } +} +greetings(); +""" + +js = JavascriptTask(task_ref_name='hello_script', script=say_hello_js, bindings={'name': '${workflow.input.name}'}) +``` + +```json +{ + "name": "inline_task", + "taskReferenceName": "inline_task_ref", + "type": "INLINE", + "inputParameters": { + "expression": " function greetings() {\n return {\n \"text\": \"hello \" + $.name\n }\n }\n greetings();", + "evaluatorType": "graaljs", + "name": "${workflow.input.name}" + } +} +``` + +#### Json Processing using JQ + +[jq](https://jqlang.github.io/jq/) is like sed for JSON data - you can use it to slice and filter and map and transform structured data with the same ease that sed, awk, grep and friends let you play with text. + +```python +from conductor.client.workflow.task.json_jq_task import JsonJQTask + +jq_script = """ +{ key3: (.key1.value1 + .key2.value2) } +""" + +jq = JsonJQTask(task_ref_name='jq_process', script=jq_script) +""" + +jq = JsonJQTask(task_ref_name='jq_process', script=jq_script) +``` + +```json +{ + "name": "json_transform_task", + "taskReferenceName": "json_transform_task_ref", + "type": "JSON_JQ_TRANSFORM", + "inputParameters": { + "key1": "k1", + "key2": "k2", + "queryExpression": "{ key3: (.key1.value1 + .key2.value2) }", + } +} +``` + +### Worker vs. Microservice / HTTP endpoints + +:::tip +Workers are a lightweight alternative to exposing an HTTP endpoint and orchestrating using an HTTP task. Using workers is a recommended approach if you do not need to expose the service over HTTP or gRPC endpoints. +::: + +There are several advantages to this approach: + +1. **No need for an API management layer**: Given there are no exposed endpoints and workers are self load-balancing. +2. **Reduced infrastructure footprint**: No need for an API gateway/load balancer. +3. All the communication is initiated from worker using polling - avoiding need to open up any incoming TCP ports. +4. Workers **self-regulate** when busy; they only poll as much as they can handle. Backpressure handling is done out of the box. +5. Workers can be scaled up / down quickly based on the demand by increasing the no. of processes. + +### Deploying Workers in production + +Conductor workers can run in the cloud-native environment or on-prem and can easily be deployed like any other Python application. Workers can run a containerized environment, VMs, or on bare-metal just like you would deploy your other Python applications. + +## Create Conductor Workflows + +Workflow can be defined as the collection of tasks and operators that specify the order and execution of the defined tasks. This orchestration occurs in a hybrid ecosystem that encircles serverless functions, microservices, and monolithic applications. + +In this section, we will dive deeper into creating and executing Conductor workflows using Python SDK. + +### Creating Workflows + +Conductor lets you create the workflows either using Python or JSON as the configuration. Using Python as code to define and execute workflows enables you to build extremely powerful, dynamic workflows and run them on Conductor. + +When the workflows are fairly static, they can be designed using the Orkes UI (available when using orkes.io) and using APIs or SDKs to register and run the workflows. + +Both the code and configuration approaches are equally powerful and similar in nature to how you treat Infrastructure as Code. + +#### Execute dynamic workflows using Code + +For cases where the workflows cannot be created statically ahead of time, Conductor is a powerful dynamic workflow execution platform that lets you create very complex workflows in code and execute them. Useful when the workflow is unique for each execution. + +```python +from conductor.client.automator.task_handler import TaskHandler +from conductor.client.configuration.configuration import Configuration +from conductor.client.orkes_clients import OrkesClients +from conductor.client.worker.worker_task import worker_task +from conductor.client.workflow.conductor_workflow import ConductorWorkflow + + +@worker_task(task_definition_name='get_user_email') +def get_user_email(userid: str) -> str: + return f'{userid}@example.com' + + +@worker_task(task_definition_name='send_email') +def send_email(email: str, subject: str, body: str): + print(f'sending email to {email} with subject {subject} and body {body}') + + +def main(): + + # defaults to reading the configuration using following env variables + # CONDUCTOR_SERVER_URL : conductor server e.g. https://play.orkes.io/api + # CONDUCTOR_AUTH_KEY : API Authentication Key + # CONDUCTOR_AUTH_SECRET: API Auth Secret + api_config = Configuration() + + task_handler = TaskHandler(configuration=api_config) + task_handler.start_processes() + + clients = OrkesClients(configuration=api_config) + workflow_executor = clients.get_workflow_executor() + workflow = ConductorWorkflow(name='dynamic_workflow', version=1, executor=workflow_executor) + get_email = get_user_email(task_ref_name='get_user_email_ref', userid=workflow.input('userid')) + sendmail = send_email(task_ref_name='send_email_ref', email=get_email.output('result'), subject='Hello from Orkes', + body='Test Email') + workflow >> get_email >> sendmail + + # Configure the output of the workflow + workflow.output_parameters(output_parameters={ + 'email': get_email.output('result') + }) + + result = workflow.execute(workflow_input={'userid': 'user_a'}) + print(f'\nworkflow output: {result.output}\n') + task_handler.stop_processes() + + +if __name__ == '__main__': + main() +``` + +```python +>> python3 dynamic_workflow.py + +2024-02-03 19:54:35,700 [32853] conductor.client.automator.task_handler INFO created worker with name=get_user_email and domain=None +2024-02-03 19:54:35,781 [32853] conductor.client.automator.task_handler INFO created worker with name=send_email and domain=None +2024-02-03 19:54:35,859 [32853] conductor.client.automator.task_handler INFO TaskHandler initialized +2024-02-03 19:54:35,859 [32853] conductor.client.automator.task_handler INFO Starting worker processes... +2024-02-03 19:54:35,861 [32853] conductor.client.automator.task_runner INFO Polling task get_user_email with domain None with polling interval 0.1 +2024-02-03 19:54:35,861 [32853] conductor.client.automator.task_handler INFO Started 2 TaskRunner process +2024-02-03 19:54:35,862 [32853] conductor.client.automator.task_handler INFO Started all processes +2024-02-03 19:54:35,862 [32853] conductor.client.automator.task_runner INFO Polling task send_email with domain None with polling interval 0.1 +sending email to user_a@example.com with subject Hello from Orkes and body Test Email + +workflow output: {'email': 'user_a@example.com'} + +2024-02-03 19:54:36,309 [32853] conductor.client.automator.task_handler INFO Stopped worker processes... +``` + +See [dynamic_workflow.py](https://github.com/conductor-sdk/conductor-python/blob/main/examples/dynamic_workflow.py) for a fully functional example. + +#### Kitchensink Workflow + +See [kitchensink.py](https://github.com/conductor-sdk/conductor-python/blob/main/examples/kitchensink.py) for a more complex example. + +### Executing Workflows + +[WorkflowClient](https://github.com/conductor-sdk/conductor-python/blob/main/src/conductor/client/workflow_client.py) interface provides all the APIs required to work with workflow executions. + +```python +from conductor.client.configuration.configuration import Configuration +from conductor.client.orkes_clients import OrkesClients + +api_config = Configuration() +clients = OrkesClients(configuration=api_config) +workflow_client = clients.get_workflow_client() +``` + +#### Execute workflow asynchronously + +Useful when workflows are long-running. + +```python +from conductor.client.http.models import StartWorkflowRequest + +request = StartWorkflowRequest() +request.name = 'hello' +request.version = 1 +request.input = {'name': 'Orkes'} +# workflow id is the unique execution id associated with this execution +workflow_id = workflow_client.start_workflow(request) +``` + +#### Execute workflow synchronously + +Useful when workflows complete very quickly - usually under 20-30 seconds. + +```python +from conductor.client.http.models import StartWorkflowRequest + +request = StartWorkflowRequest() +request.name = 'hello' +request.version = 1 +request.input = {'name': 'Orkes'} + +workflow_run = workflow_client.execute_workflow( + start_workflow_request=request, + wait_for_seconds=12) +``` + +### Managing Workflow Executions + +:::note +See [workflow_ops.py](https://github.com/conductor-sdk/conductor-python/blob/main/examples/workflow_ops.py) for a fully working application that demonstrates working with the workflow executions and sending signals to the workflow to manage its state. +::: + +Workflows represent te application state. With Conductor, you can query the workflow execution state anytime during its lifecycle. You can also send Signals to the workflow that determines the outcome of the workflow state. + +[WorkflowClient](https://github.com/conductor-sdk/conductor-python/blob/main/src/conductor/client/workflow_client.py) is the client interface used to manage workflow executions. + +```python +from conductor.client.configuration.configuration import Configuration +from conductor.client.orkes_clients import OrkesClients + +api_config = Configuration() +clients = OrkesClients(configuration=api_config) +workflow_client = clients.get_workflow_client() +``` + +#### Get the execution status + +The following method lets you query the status of the workflow execution given the id. When the **include_tasks** is set the response also includes all the completed and in progress tasks. + +``` +get_workflow(workflow_id: str, include_tasks: Optional[bool] = True) -> Workflow +``` + +#### Update workflow state variables + +Variables inside a workflow are the equivalent of global variables in a program. + +``` +update_variables(self, workflow_id: str, variables: dict[str, object] = {}) +``` + +#### Terminate running workflows + +Terminates a running workflow. Any pending tasks are cancelled and no further work is scheduled for this workflow upon termination. A failure workflow will be triggered, but can be avoided if **trigger_failure_workflow** is set to False. + +``` +terminate_workflow(self, workflow_id: str, reason: Optional[str] = None, trigger_failure_workflow: bool = False) +``` + +#### Retry failed workflows + +If the workflow has failed due to one of the task failures after exhausting the retries for the task, the workflow can still be resumed by calling the retry. + +``` +retry_workflow(self, workflow_id: str, resume_subworkflow_tasks: Optional[bool] = False) +``` + +When a sub-workflow inside a workflow has failed, there are two options: + +1. Re-trigger the sub-workflow from the start (Default behavior) +2. Resume the sub-workflow from the failed task (set resume_subworkflow_tasks to True) + +#### Restart workflows + +A workflow in the terminal state (COMPLETED, TERMINATED, FAILED) can be restarted from the beginning. Useful when retrying from the last failed task is insufficient, and the whole workflow must be started again. + +``` +restart_workflow(self, workflow_id: str, use_latest_def: Optional[bool] = False) +``` + +#### Rerun a workflow from a specific task + + +In the cases where a workflow needs to be restarted from a specific task rather than from the beginning, **re-run** provides that option. When issuing the re-run command to the workflow, you have the ability to specify the id of the task from where the workflow should be restarted (as opposed to from the beginning) and optionally, the input of the workflow can also be changed: + +``` +rerun_workflow(self, workflow_id: str, rerun_workflow_request: RerunWorkflowRequest) +``` + +:::tip +Re-run is one of the most powerful features of Conductor, giving you unparalleled control over the restart of workflow. +::: + +#### Pause a running workflow + +A running workflow can be put to a PAUSED status. A paused workflow lets the currently running tasks be completed but does not schedule any new tasks until resumed. + +``` +pause_workflow(self, workflow_id: str) +``` + +#### Resume paused workflow + +Resume operation resumes the currently paused workflow, immediately evaluating its state and scheduling the next set of tasks. + +``` +resume_workflow(self, workflow_id: str) +``` + +### Searching for workflows + +Workflow executions are retained until removed from Conductor. This gives complete visibility into all the executions an application has - regardless of the number of executions. Conductor has a poewrful search API that allows you to search for workflow executions. + +``` +search(self, start, size, free_text: str = '*', query: str = None) -> ScrollableSearchResultWorkflowSummary +``` + +- **free_text**: Free text search to look for specific words in the workflow and task input/output +- **query**: SQL like query to search against specific fields in the workflow. + +Supported fields for query: + +| Field | Description | +| ----- | ----------- | +| status | Workflow status | +| correlationId | Correlation Id | +| workflowType | Name of the workflow | +| version | Workflow version | +| startTime | Start time of the workflow in unix millis | + +### Handling Failures, Retries and Rate Limits + +Conductor lets you embrace failures rather than worry about failures and complexities that are introduced in the system to handle failures. + +All aspects of handling failures, retries, rate limits, etc., are driven by the configuration that can be updated in real time without having to redeploy your application. + +#### Retries + +Each task in Conductor workflow can be configured to handle failures with retries, along with the retry policy (linear, fixed, exponential backoff) and maximum number of retry attempts allowed. + +See [Error Handling](https://orkes.io/content/error-handling) for more details. + +#### Rate Limits + +What happens when a task is operating on a critical resource that can only handle so many requests at a time? Tasks can be configured to have a fixed concurrency (X request at a time) or a rate (Y tasks/time window). + +##### Task Registration + +```python +from conductor.client.configuration.configuration import Configuration +from conductor.client.http.models import TaskDef +from conductor.client.orkes_clients import OrkesClients + + +def main(): + api_config = Configuration() + clients = OrkesClients(configuration=api_config) + metadata_client = clients.get_metadata_client() + + task_def = TaskDef() + task_def.name = 'task_with_retries' + task_def.retry_count = 3 + task_def.retry_logic = 'LINEAR_BACKOFF' + task_def.retry_delay_seconds = 1 + + # only allow 3 tasks at a time to be in the IN_PROGRESS status + task_def.concurrent_exec_limit = 3 + + # timeout the task if not polled within 60 seconds of scheduling + task_def.poll_timeout_seconds = 60 + + # timeout the task if the task does not COMPLETE in 2 minutes + task_def.timeout_seconds = 120 + + # for the long running tasks, timeout if the task does not get updated in COMPLETED or IN_PROGRESS status in + # 60 seconds after the last update + task_def.response_timeout_seconds = 60 + + # only allow 100 executions in a 10-second window! -- Note, this is complementary to concurrent_exec_limit + task_def.rate_limit_per_frequency = 100 + task_def.rate_limit_frequency_in_seconds = 10 + + metadata_client.register_task_def(task_def=task_def) +``` + +```json +{ + "name": "task_with_retries", + + "retryCount": 3, + "retryLogic": "LINEAR_BACKOFF", + "retryDelaySeconds": 1, + "backoffScaleFactor": 1, + + "timeoutSeconds": 120, + "responseTimeoutSeconds": 60, + "pollTimeoutSeconds": 60, + "timeoutPolicy": "TIME_OUT_WF", + + "concurrentExecLimit": 3, + + "rateLimitPerFrequency": 0, + "rateLimitFrequencyInSeconds": 1 +} +``` + +Update the task definition: + +``` +POST /api/metadata/taskdef -d @task_def.json +``` + +See [task_configure.py](https://github.com/conductor-sdk/conductor-python/blob/main/examples/task_configure.py) for a detailed working app. + +## Using Conductor in your Application + +Conductor SDKs are very lightweight and can easily be added to your existing or new Python app. In this section, we will dive deeper into integrating Conductor in your application. + +### Adding Conductor SDK to your application + +Conductor Python SDKs are published on PyPi at https://pypi.org/project/conductor-python/ + +``` +pip3 install conductor-python +``` + +### Testing your workflows + +Conductor SDK for Python provides a full feature testing framework for your workflow-based applications. The framework works well with any testing framework you prefer to use without imposing any specific framework. + +Conductor server provides a test endpoint **POST /api/workflow/test** that allows you to post a workflow along with the test execution data to evaluate the workflow. + +The goal of the test framework is as follows: + +1. Ability to test the various branches of the workflow. +2. Confirm the execution of the workflow and tasks given fixed set of inputs and outputs. +3. Validate that the workflow completes or fails given specific inputs. + +Here are example assertions from the test: + +```python + +... +test_request = WorkflowTestRequest(name=wf.name, version=wf.version, + task_ref_to_mock_output=task_ref_to_mock_output, + workflow_def=wf.to_workflow_def()) +run = workflow_client.test_workflow(test_request=test_request) + +print(f'completed the test run') +print(f'status: {run.status}') +self.assertEqual(run.status, 'COMPLETED') + +... +``` + +:::note +Workflow workers are your regular python functions and can be tested with any of the available testing frameworks. +::: + +#### Example Unit Testing application + +See [test_workflows.py](https://github.com/conductor-sdk/conductor-python/blob/main/examples/test_workflows.py) for a fully functional example of how to test a moderately complex workflow with branches. + +### Workflow deployments using CI/CD + +:::tip +Treat your workflow definitions just like your code. Suppose you are defining the workflows using UI. In that case, we recommend checking the JSON configuration into the version control and using your development workflow for CI/CD to promote the workflow definitions across various environments such as Dev, Test, and Prod. +::: + +Here is a recommended approach when defining workflows using JSON: + +- Treat your workflow metadata as code. +- Check in the workflow and task definitions along with the application code. +- Use **POST /api/metadata/*** endpoints or MetadataClient (**from conductor.client.metadata_client import MetadataClient**) to register/update workflows as part of the deployment process. +- Version your workflows. If there is a significant change, change the version field of the workflow. See Versioning workflows below for more details. + +### Versioning workflows + +A powerful feature of Conductor is ability to version workflows. You should increment the version of the workflow when there is a significant change to the definition. You can run multiple versions of the workflow at the same time. When starting a new workflow execution, use the **version** field to specify which version to use. When omitted, the latest (highest numbered) version is used. + +- Versioning allows safely testing changes by doing canary testing in production or A/B testing across multiple versions before rolling out. +- A version can be deleted as well, effectively allowing for "rollback" if required.