7e5abd504f
Add three DBOS SDK skills with reference documentation for building reliable, fault-tolerant applications with durable workflows. Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
71 lines
1.6 KiB
Markdown
71 lines
1.6 KiB
Markdown
---
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title: Follow Workflow Constraints
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impact: CRITICAL
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impactDescription: Violating constraints causes failures or incorrect behavior
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tags: workflow, step, constraints, rules
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---
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## Follow Workflow Constraints
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DBOS workflows and steps have specific constraints that must be followed for correct operation.
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**Incorrect (calling start_workflow from step):**
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```python
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@DBOS.step()
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def my_step():
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# Never start workflows from inside a step!
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DBOS.start_workflow(another_workflow)
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```
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**Incorrect (modifying global state):**
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```python
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results = [] # Global variable
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@DBOS.workflow()
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def my_workflow():
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# Don't modify globals from workflows!
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results.append("done")
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```
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**Incorrect (using recv outside workflow):**
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```python
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@DBOS.step()
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def my_step():
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# recv can only be called from workflows!
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msg = DBOS.recv("topic")
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```
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**Correct (following constraints):**
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```python
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@DBOS.workflow()
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def parent_workflow():
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result = my_step()
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# Start child workflow from workflow, not step
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handle = DBOS.start_workflow(child_workflow, result)
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# Use recv from workflow
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msg = DBOS.recv("topic")
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return handle.get_result()
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@DBOS.step()
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def my_step():
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# Steps just do their work and return
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return process_data()
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@DBOS.workflow()
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def child_workflow(data):
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return transform(data)
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```
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Key constraints:
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- Do NOT call `DBOS.start_workflow` from a step
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- Do NOT call `DBOS.recv` from a step
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- Do NOT call `DBOS.set_event` from outside a workflow
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- Do NOT modify global variables from workflows or steps
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- Do NOT use threads to start workflows
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Reference: [DBOS Workflows](https://docs.dbos.dev/python/tutorials/workflow-tutorial)
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