Added updatable timer sample.

.gitignore

@@ -1,2 +1,3 @@
 .venv
+.idea
 __pycache__

README.md

@@ -73,6 +73,7 @@ Some examples require extra dependencies. See each sample's directory for specif
 * [schedules](schedules) - Demonstrates a Workflow Execution that occurs according to a schedule.
 * [sentry](sentry) - Report errors to Sentry.
 * [trio_async](trio_async) - Use asyncio Temporal in Trio-based environments.
+* [updatable_timer](updatable_timer) - A timer that can be updated while sleeping.
 * [worker_specific_task_queues](worker_specific_task_queues) - Use unique task queues to ensure activities run on specific workers.
 * [worker_versioning](worker_versioning) - Use the Worker Versioning feature to more easily version your workflows & other code.
 

updatable_timer/README.md

@@ -0,0 +1,42 @@
+# Updatable Timer Sample
+
+Demonstrates a helper class which relies on `workflow.wait_condition` to implement a blocking sleep that can be updated at any moment.
+
+The sample is composed of the three executables:
+
+* `worker.py` hosts the Workflow Executions.
+* `starter.py` starts Workflow Executions.
+* `wake_up_timer_updater.py` Signals the Workflow Execution with the new time to wake up.
+
+First start the Worker:
+
+```bash
+poetry run python worker.py
+```
+Check the output of the Worker window. The expected output is:
+
+```
+Worker started, ctrl+c to exit
+```
+
+Then in a different terminal window start the Workflow Execution:
+
+```bash
+poetry run python starter.py
+```
+Check the output of the Worker window. The expected output is:
+```
+Workflow started: run_id=...
+```
+
+Then run the updater as many times as you want to change timer to 10 seconds from now:
+
+```bash
+poetry run python wake_up_time_updater.py
+```
+
+Check the output of the worker window. The expected output is:
+
+```
+Updated wake up time to 10 seconds from now
+```

updatable_timer/__init__.py

@@ -0,0 +1 @@
+TASK_QUEUE = "updatable-timer"

updatable_timer/starter.py

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+import asyncio
+import logging
+from datetime import datetime, timedelta
+from typing import Optional
+
+from temporalio import exceptions
+from temporalio.client import Client
+
+from updatable_timer import TASK_QUEUE
+from updatable_timer.workflow import Workflow
+
+
+async def main(client: Optional[Client] = None):
+    logging.basicConfig(level=logging.INFO)
+
+    client = client or await Client.connect("localhost:7233")
+    try:
+        handle = await client.start_workflow(
+            Workflow.run,
+            (datetime.now() + timedelta(days=1)).timestamp(),
+            id=f"updatable-timer-workflow",
+            task_queue=TASK_QUEUE,
+        )
+        logging.info(f"Workflow started: run_id={handle.result_run_id}")
+    except exceptions.WorkflowAlreadyStartedError as e:
+        logging.info(
+            f"Workflow already running: workflow_id={e.workflow_id}, run_id={e.run_id}"
+        )
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

updatable_timer/updatable_timer_lib.py

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+import asyncio
+from datetime import datetime, timedelta
+
+from temporalio import workflow
+
+
+class UpdatableTimer:
+    def __init__(self, wake_up_time: datetime) -> None:
+        self.wake_up_time = wake_up_time
+        self.wake_up_time_updated = False
+
+    async def sleep(self) -> None:
+        workflow.logger.info(f"sleep_until: {self.wake_up_time}")
+        while True:
+            now = workflow.now()
+
+            sleep_interval = self.wake_up_time - now
+            if sleep_interval <= timedelta(0):
+                break
+            workflow.logger.info(f"Going to sleep for {sleep_interval}")
+
+            try:
+                self.wake_up_time_updated = False
+                await workflow.wait_condition(
+                    lambda: self.wake_up_time_updated,
+                    timeout=sleep_interval,
+                )
+            except asyncio.TimeoutError:
+                # checks condition at the beginning of the loop
+                continue
+        workflow.logger.info(f"sleep_until completed")
+
+    def update_wake_up_time(self, wake_up_time: datetime) -> None:
+        workflow.logger.info(f"update_wake_up_time:  {wake_up_time}")
+        self.wake_up_time = wake_up_time
+        self.wake_up_time_updated = True
+
+    def get_wake_up_time(self) -> datetime:
+        return self.wake_up_time

updatable_timer/wake_up_time_updater.py

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+import asyncio
+import logging
+from datetime import datetime, timedelta
+from typing import Optional
+
+from temporalio.client import Client
+
+from updatable_timer.workflow import Workflow
+
+
+async def main(client: Optional[Client] = None):
+    logging.basicConfig(level=logging.INFO)
+
+    client = client or await Client.connect("localhost:7233")
+    handle = client.get_workflow_handle(workflow_id="updatable-timer-workflow")
+    # signal workflow about the wake up time change
+    await handle.signal(
+        Workflow.update_wake_up_time,
+        (datetime.now() + timedelta(seconds=10)).timestamp(),
+    )
+
+    logging.info("Updated wake up time to 10 seconds from now")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

updatable_timer/worker.py

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+import asyncio
+import logging
+
+from temporalio.client import Client
+from temporalio.worker import Worker
+
+from updatable_timer import TASK_QUEUE
+from updatable_timer.workflow import Workflow
+
+interrupt_event = asyncio.Event()
+
+
+async def main():
+    logging.basicConfig(level=logging.INFO)
+
+    client = await Client.connect("localhost:7233")
+    async with Worker(
+        client,
+        task_queue=TASK_QUEUE,
+        workflows=[Workflow],
+    ):
+        logging.info("Worker started, ctrl+c to exit")
+        # Wait until interrupted
+        await interrupt_event.wait()
+        logging.info("Interrupt received, shutting down...")
+
+
+if __name__ == "__main__":
+    loop = asyncio.new_event_loop()
+    asyncio.set_event_loop(loop)
+    try:
+        loop.run_until_complete(main())
+    except KeyboardInterrupt:
+        interrupt_event.set()
+        loop.run_until_complete(loop.shutdown_asyncgens())

updatable_timer/workflow.py

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+from datetime import datetime, timezone
+from typing import Optional
+
+from temporalio import workflow
+
+from updatable_timer.updatable_timer_lib import UpdatableTimer
+
+
+@workflow.defn
+class Workflow:
+    def __init__(self):
+        self.timer: Optional[UpdatableTimer] = None
+
+    @workflow.run
+    async def run(self, wake_up_time: float):
+        self.timer = UpdatableTimer(
+            datetime.fromtimestamp(wake_up_time, tz=timezone.utc)
+        )
+        await self.timer.sleep()
+
+    @workflow.signal
+    async def update_wake_up_time(self, wake_up_time: float):
+        # Deals with situation when the signal method is called before the run method.
+        # This happens when a workflow task is executed after a signal is received
+        # or when a workflow is started using the signal-with-start.
+        await workflow.wait_condition(lambda: self.timer is not None)
+        assert self.timer is not None  # for mypy
+        self.timer.update_wake_up_time(
+            datetime.fromtimestamp(wake_up_time, tz=timezone.utc)
+        )
+
+    @workflow.query
+    def get_wake_up_time(self):
+        assert self.timer is not None  # for mypy
+        return self.timer.get_wake_up_time()