DSL sample (#87)

Fixes #7

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
       # Using fixed Poetry version until
       # https://github.com/python-poetry/poetry/pull/7694 is fixed
       - run: python -m pip install --upgrade wheel "poetry==1.4.0" poethepoet
-      - run: poetry install --with pydantic
+      - run: poetry install --with pydantic --with dsl
       - run: poe lint
       - run: poe test -s -o log_cli_level=DEBUG
       - run: poe test -s -o log_cli_level=DEBUG --workflow-environment time-skipping

README.md

@@ -55,6 +55,7 @@ Some examples require extra dependencies. See each sample's directory for specif
 * [activity_worker](activity_worker) - Use Python activities from a workflow in another language.
 * [custom_converter](custom_converter) - Use a custom payload converter to handle custom types.
 * [custom_decorator](custom_decorator) - Custom decorator to auto-heartbeat a long-running activity.
+* [dsl](dsl) - DSL workflow that executes steps defined in a YAML file.
 * [encryption](encryption) - Apply end-to-end encryption for all input/output.
 * [gevent_async](gevent_async) - Combine gevent and Temporal.
 * [open_telemetry](open_telemetry) - Trace workflows with OpenTelemetry.

dsl/README.md

@@ -0,0 +1,29 @@
+# DSL Sample
+
+This sample shows how to have a workflow interpret/invoke arbitrary steps defined in a DSL. It is similar to the DSL
+samples [in TypeScript](https://github.com/temporalio/samples-typescript/tree/main/dsl-interpreter) and
+[in Go](https://github.com/temporalio/samples-go/tree/main/dsl).
+
+For this sample, the optional `dsl` dependency group must be included. To include, run:
+
+    poetry install --with dsl
+
+To run, first see [README.md](../README.md) for prerequisites. Then, run the following from this directory to start the
+worker:
+
+    poetry run python worker.py
+
+This will start the worker. Then, in another terminal, run the following to execute a workflow of steps defined in
+[workflow1.yaml](workflow1.yaml):
+
+    poetry run python starter.py workflow1.yaml
+
+This will run the workflow and show the final variables that the workflow returns. Looking in the worker terminal, each
+step executed will be visible.
+
+Similarly we can do the same for the more advanced [workflow2.yaml](workflow2.yaml) file:
+
+    poetry run python starter.py workflow2.yaml
+
+This sample gives a guide of how one can write a workflow to interpret arbitrary steps from a user-provided DSL. Many
+DSL models are more advanced and are more specific to conform to business logic needs.

dsl/activities.py

@@ -0,0 +1,28 @@
+from temporalio import activity
+
+
+class DSLActivities:
+    @activity.defn
+    async def activity1(self, arg: str) -> str:
+        activity.logger.info(f"Executing activity1 with arg: {arg}")
+        return f"[result from activity1: {arg}]"
+
+    @activity.defn
+    async def activity2(self, arg: str) -> str:
+        activity.logger.info(f"Executing activity2 with arg: {arg}")
+        return f"[result from activity2: {arg}]"
+
+    @activity.defn
+    async def activity3(self, arg1: str, arg2: str) -> str:
+        activity.logger.info(f"Executing activity3 with args: {arg1} and {arg2}")
+        return f"[result from activity3: {arg1} {arg2}]"
+
+    @activity.defn
+    async def activity4(self, arg: str) -> str:
+        activity.logger.info(f"Executing activity4 with arg: {arg}")
+        return f"[result from activity4: {arg}]"
+
+    @activity.defn
+    async def activity5(self, arg1: str, arg2: str) -> str:
+        activity.logger.info(f"Executing activity5 with args: {arg1} and {arg2}")
+        return f"[result from activity5: {arg1} {arg2}]"

dsl/starter.py

@@ -0,0 +1,46 @@
+import asyncio
+import logging
+import sys
+import uuid
+
+import dacite
+import yaml
+from temporalio.client import Client
+
+from dsl.workflow import DSLInput, DSLWorkflow
+
+
+async def main(dsl_yaml: str) -> None:
+    # Convert the YAML to our dataclass structure. We use PyYAML + dacite to do
+    # this but it can be done any number of ways.
+    dsl_input = dacite.from_dict(DSLInput, yaml.safe_load(dsl_yaml))
+
+    # Connect client
+    client = await Client.connect("localhost:7233")
+
+    # Run workflow
+    result = await client.execute_workflow(
+        DSLWorkflow.run,
+        dsl_input,
+        id=f"dsl-workflow-id-{uuid.uuid4()}",
+        task_queue="dsl-task-queue",
+    )
+    logging.info(
+        f"Final variables:\n    "
+        + "\n    ".join((f"{k}: {v}" for k, v in result.items()))
+    )
+
+
+if __name__ == "__main__":
+    logging.basicConfig(level=logging.INFO)
+
+    # Require the YAML file as an argument. We read this _outside_ of the async
+    # def function because thread-blocking IO should never happen in async def
+    # functions.
+    if len(sys.argv) != 2:
+        raise RuntimeError("Expected single argument for YAML file")
+    with open(sys.argv[1], "r") as yaml_file:
+        dsl_yaml = yaml_file.read()
+
+    # Run
+    asyncio.run(main(dsl_yaml))

dsl/worker.py

@@ -0,0 +1,44 @@
+import asyncio
+import logging
+
+from temporalio.client import Client
+from temporalio.worker import Worker
+
+from dsl.activities import DSLActivities
+from dsl.workflow import DSLWorkflow
+
+interrupt_event = asyncio.Event()
+
+
+async def main():
+    # Connect client
+    client = await Client.connect("localhost:7233")
+
+    # Run a worker for the activities and workflow
+    activities = DSLActivities()
+    async with Worker(
+        client,
+        task_queue="dsl-task-queue",
+        activities=[
+            activities.activity1,
+            activities.activity2,
+            activities.activity3,
+            activities.activity4,
+            activities.activity5,
+        ],
+        workflows=[DSLWorkflow],
+    ):
+        # Wait until interrupted
+        logging.info("Worker started, ctrl+c to exit")
+        await interrupt_event.wait()
+        logging.info("Shutting down")
+
+
+if __name__ == "__main__":
+    logging.basicConfig(level=logging.INFO)
+    loop = asyncio.new_event_loop()
+    try:
+        loop.run_until_complete(main())
+    except KeyboardInterrupt:
+        interrupt_event.set()
+        loop.run_until_complete(loop.shutdown_asyncgens())

dsl/workflow.py

@@ -0,0 +1,85 @@
+from __future__ import annotations
+
+import asyncio
+import dataclasses
+from dataclasses import dataclass
+from datetime import timedelta
+from typing import Any, Dict, List, Optional, Union
+
+from temporalio import workflow
+
+
+@dataclass
+class DSLInput:
+    root: Statement
+    variables: Dict[str, Any] = dataclasses.field(default_factory=dict)
+
+
+@dataclass
+class ActivityStatement:
+    activity: ActivityInvocation
+
+
+@dataclass
+class ActivityInvocation:
+    name: str
+    arguments: List[str] = dataclasses.field(default_factory=list)
+    result: Optional[str] = None
+
+
+@dataclass
+class SequenceStatement:
+    sequence: Sequence
+
+
+@dataclass
+class Sequence:
+    elements: List[Statement]
+
+
+@dataclass
+class ParallelStatement:
+    parallel: Parallel
+
+
+@dataclass
+class Parallel:
+    branches: List[Statement]
+
+
+Statement = Union[ActivityStatement, SequenceStatement, ParallelStatement]
+
+
+@workflow.defn
+class DSLWorkflow:
+    @workflow.run
+    async def run(self, input: DSLInput) -> Dict[str, Any]:
+        self.variables = dict(input.variables)
+        workflow.logger.info("Running DSL workflow")
+        await self.execute_statement(input.root)
+        workflow.logger.info("DSL workflow completed")
+        return self.variables
+
+    async def execute_statement(self, stmt: Statement) -> None:
+        if isinstance(stmt, ActivityStatement):
+            # Invoke activity loading arguments from variables and optionally
+            # storing result as a variable
+            result = await workflow.execute_activity(
+                stmt.activity.name,
+                args=[self.variables.get(arg, "") for arg in stmt.activity.arguments],
+                start_to_close_timeout=timedelta(minutes=1),
+            )
+            if stmt.activity.result:
+                self.variables[stmt.activity.result] = result
+        elif isinstance(stmt, SequenceStatement):
+            # Execute each statement in order
+            for elem in stmt.sequence.elements:
+                await self.execute_statement(elem)
+        elif isinstance(stmt, ParallelStatement):
+            # Execute all in parallel. Note, this will raise an exception when
+            # the first activity fails and will not cancel the others. We could
+            # store tasks and cancel if we wanted. In newer Python versions this
+            # would use a TaskGroup instead.
+            await asyncio.gather(
+                *[self.execute_statement(branch) for branch in stmt.parallel.branches]
+            )

dsl/workflow1.yaml

@@ -0,0 +1,28 @@
+# This sample workflows execute 3 steps in sequence.
+# 1) Activity1, takes arg1 as input, and put result as result1.
+# 2) Activity2, takes result1 as input, and put result as result2.
+# 3) Activity3, takes args2 and result2 as input, and put result as result3.
+
+variables:
+  arg1: value1
+  arg2: value2
+
+root:
+  sequence:
+    elements:
+      - activity:
+          name: activity1
+          arguments:
+            - arg1
+          result: result1
+      - activity:
+          name: activity2
+          arguments:
+            - result1
+          result: result2
+      - activity:
+          name: activity3
+          arguments:
+            - arg2
+            - result2
+          result: result3

dsl/workflow2.yaml

@@ -0,0 +1,58 @@
+# This sample workflow executes 3 steps in sequence.
+# 1) activity1, takes arg1 as input, and put result as result1.
+# 2) it runs a parallel block which runs below sequence branches in parallel
+#  2.1) sequence 1
+#    2.1.1) activity2, takes result1 as input, and put result as result2
+#    2.1.2) activity3, takes arg2 and result2 as input, and put result as result3
+#  2.2) sequence 2
+#    2.2.1) activity4, takes result1 as input, and put result as result4
+#    2.2.2) activity5, takes arg3 and result4 as input, and put result as result5
+# 3) activity3, takes result3 and result5 as input, and put result as result6.
+
+variables:
+  arg1: value1
+  arg2: value2
+  arg3: value3
+
+root:
+  sequence:
+    elements:
+      - activity:
+          name: activity1
+          arguments:
+            - arg1
+          result: result1
+      - parallel:
+          branches:
+            - sequence:
+                elements:
+                  - activity:
+                      name: activity2
+                      arguments:
+                        - result1
+                      result: result2
+                  - activity:
+                      name: activity3
+                      arguments:
+                        - arg2
+                        - result2
+                      result: result3
+            - sequence:
+                elements:
+                  - activity:
+                      name: activity4
+                      arguments:
+                        - result1
+                      result: result4
+                  - activity:
+                      name: activity5
+                      arguments:
+                        - arg3
+                        - result4
+                      result: result5
+      - activity:
+          name: activity3
+          arguments:
+            - result3
+            - result5
+          result: result6