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<@ULVA73B9P> my workers cant start Discovered type...
# ask-marvin
s
@Marvin my workers cant start Discovered type 'process' for work pool 'default'. Worker 'ProcessWorker 6c90b577-ffe6-45a4-b4e8-6a0fe718f982' started! 000846.326 | INFO | prefect.workers.process.processworker 6c90b577-ffe6-45a4-b4e8-6a0fe718f982 - Found 1 flow runs awaiting cancellation. 000846.392 | WARNING | prefect.workers.process.processworker 6c90b577-ffe6-45a4-b4e8-6a0fe718f982 - Unable to kill process 19796: The process was not found. Marking flow run as cancelled.
m
It looks like you're experiencing an issue with a Prefect worker, where it is unable to cancel a flow run due to a missing process. This kind of issue can happen for various reasons, such as changes in the system's process handling or the flow run state not being synchronized correctly with the actual running processes. Unfortunately, I couldn't find a direct match for this specific error message in the Prefect documentation. However, you might want to try a few general troubleshooting steps: 1. Restart the Worker: Sometimes, simply restarting the worker can help clear small glitches. Make sure no orphaned processes are running after the restart. 2. Check System Resources: Ensure your system has enough resources. If the system is running low on memory or CPU, it might be terminating processes unexpectedly. 3. Verify Installation: Ensure that Prefect and all dependencies are correctly installed and updated. Outdated or mismatched versions might cause unexpected behavior. 4. Review Worker Configuration: Double-check any environment variables or configuration settings associated with your Prefect worker, as these might affect how processes are started and managed. 5. Check Logs: Look through the Prefect logs for any additional hints or errors that might give more context about why the process cannot be found. For more detailed guidance or potential updates related to this issue, you can follow these links to explore the Prefect documentation and tutorials for more background and possible solutions: - Prefect 2.x documentation: Databricks Issues - Prefect 3.x documentation: Worker Deployment and Troubleshooting If your issue persists, consider checking Prefect's community forums or GitHub issues to see if anyone else has encountered and resolved a similar problem. Hopefully, this helps you get back to a smoothly functioning worker!
s
@Marvin how to force stop worker
m
To force stop a worker in Prefect, you may typically need to manage the worker process directly since there's no built-in "hard stop" command in Prefect's CLI or API. Here are some general methods: 1. Use the Operating System's Process Management: - Linux/Mac: You can use the 
kill
command followed by the process ID (PID) of the worker to stop it. Use 
kill -9 PID
for a forced stop. - Windows: Use 
Task Manager
to find the Prefect worker and end the task, or use 
taskkill
in the command prompt with the 
/F
flag for a forced shutdown. 2. Prefect CLI Command: If you're able to access the worker from the Prefect infrastructure, try using the CLI to stop it gracefully, although this may not "force" a stop:
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prefect worker stop [OPTIONS]
Replace 
[OPTIONS]
with any specific options or identifiers for your worker. Unfortunately, the Prefect documentation does not provide direct commands for force-stopping a worker, as seen in the document excerpts (Prefect Worker Concepts). It mainly covers how workers operate within work pools and the types of infrastructure they support. Thus, using your system's process management tools is the most practical approach for forcefully stopping them. And don't worry, preferring a methodical shutdown over a melodramatic "off with their heads" approach is relatively common in programming.
s
@Marvin No such command 'stop'.
m
Ah, it seems I led us astray there for a moment like a faulty GPS. Indeed, Prefect doesn't have a native CLI command specifically to "stop" a worker, which means you'll have to rely on your operating system's process management to handle this. Here are your options: 1. Identify the Worker Process: - Linux/Mac: Use 
ps aux | grep prefect
to find the worker's process ID (PID). - Windows: Use 
tasklist
or open 
Task Manager
to locate the process. 2. Terminate the Worker Process: - Linux/Mac: Use 
kill -9 <PID>
to forcefully stop the process. Note that 
-9
sends the SIGKILL signal, which ungracefully kills the process. Use with caution! - Windows: Execute 
taskkill /PID <PID> /F
in the command prompt to forcefully terminate the process. These methods should enable you to effectively manage your worker processes, even sans a dedicated "stop" command within Prefect's CLI. If you encounter any difficulties, feel free to share, and we'll debug it together—like the trusty companions we are.
s
i killed all python processes, but still worker cant start
@Marvin i killed all python processes, but still worker cant start | Traceback (most recent call last): | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 340, in kill_process | os.kill(pid, signal.CTRL_BREAK_EVENT) | OSError: [WinError 11] An attempt was made to load a program with an incorrect format | | During handling of the above exception, another exception occurred: | | Traceback (most recent call last): | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 478, in cancel_run | await self.kill_process( | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 342, in kill_process | raise InfrastructureNotFound( | prefect.exceptions.InfrastructureNotFound: Unable to kill process 19796: The process was not found. | | During handling of the above exception, another exception occurred: | | Traceback (most recent call last): | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 488, in cancel_run | await self._mark_flow_run_as_cancelled(flow_run) | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\base.py", line 1148, in _mark_flow_run_as_cancelled | await self._client.set_flow_run_state(flow_run.id, state, force=True) | File "C:\dev\zeus\venv\Lib\site-packages\prefect\client\orchestration.py", line 2180, in set_flow_run_state | state=state_create.model_dump(mode="json", serialize_as_any=True), | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | File "C:\dev\zeus\venv\Lib\site-packages\pydantic\main.py", line 390, in model_dump | return self.__pydantic_serializer__.to_python( | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | TypeError: 'MockValSer' object cannot be converted to 'SchemaSerializer'
m
Your message was too long by 242 tokens - please shorten it and try again. For reference, here's your message at the allowed limit:
i killed all python processes, but still worker cant start
| Traceback (most recent call last): | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 340, in kill_process | os.kill(pid, signal.CTRL_BREAK_EVENT) | OSError: [WinError 11] An attempt was made to load a program with an incorrect format | | During handling of the above exception, another exception occurred: | | Traceback (most recent call last): | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 478, in cancel_run | await self.kill_process( | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 342, in kill_process | raise InfrastructureNotFound( | prefect.exceptions.InfrastructureNotFound: Unable to kill process 19796: The process was not found. | | During handling of the above exception, another exception occurred: | | Traceback (most recent call last): | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 488, in cancel_run
s
@Marvin killed all python processes, but still worker cant start
| Traceback (most recent call last): | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 340, in kill_process | os.kill(pid, signal.CTRL_BREAK_EVENT) | OSError: [WinError 11] An attempt was made to load a program with an incorrect format | | During handling of the above exception, another exception occurred: | | Traceback (most recent call last): | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 478, in cancel_run | await self.kill_process( | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 342, in kill_process | raise InfrastructureNotFound( | prefect.exceptions.InfrastructureNotFound: Unable to kill process 19796: The process was not found. | | During handling of the above exception, another exception occurred: | | Traceback (most recent call last): | File "C:\dev\zeus\venv\Lib\site-packages\prefect\workers\process.py", line 488, in cancel_run
m
It seems like your Prefect worker is encountering an issue with Windows-specific process management. The 
OSError: [WinError 11]
typically indicates a problem with the attempt to send a signal to a process that doesn't match the expected format, or it might not exist anymore, leading to an 
InfrastructureNotFound
error. This can occur if: 1. Process ID Misalignment: The worker attempts to kill a process using an incorrect PID, perhaps because the process has already terminated on its own. 2. Signal Handling on Windows: The signal being sent (
CTRL_BREAK_EVENT
) is suitable for certain applications and might not be supported by your environment or process. Here's a couple of things you can try: - Ensure Correct Python Bit Version: Sometimes this error pops up if there’s a mismatch between 32-bit and 64-bit versions of Python and the operating system. Make sure your Python version matches your OS architecture. - Check for Background Processes: Ensure that there are no leftover background Python processes that might interfere with launching a new worker. - Update Prefect and Dependencies: Ensure you're using the latest Prefect version and all dependencies are up-to-date. Outdated packages can occasionally cause such mishaps due to missing patches. These issues can be subtle and system-specific, so it might take some trial and error to identify the exact cause. If the problem persists, consider reaching out to the Prefect community on their Discuss Forum for more targeted help, as someone might have encountered and resolved a similar issue.
s
@Marvin i think need to just clean prefect database from running workers
m
To clean up Prefect's database and remove records of "running" workers, you typically interact with the backend database where Prefect stores its state. Here are some high-level steps you can follow: 1. Access the Database: If you're running Prefect with a PostgreSQL backend (common for Prefect Server), you'll need access to the PostgreSQL database. Use a tool like 
psql
or any SQL client. 2. Identify Worker Records: Depending on your database schema, identify the tables that contain running or scheduled worker information. Common tables might include 
flow_runs
, 
tasks
, or other worker-related tables. 3. Backup the Database: Before making any changes, ensure you have a backup of your database. This step is vital to prevent data loss or unforeseen issues. 4. Run Cleanup Commands: - For PostgreSQL, you can execute SQL commands to delete or update records. Here's a generalized command to delete running flows:
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sql
     DELETE FROM flow_runs WHERE state = 'Running';
- Adjust the command to match your schema and target the correct status or table. 5. Restart Prefect Services: After cleanup, restart your Prefect services to apply changes and ensure the system recognizes the updated state. If you're using Prefect Cloud, you may need to utilize Prefect's API or reach out to their support, as direct database access is not applicable. Be cautious with direct database modifications—like giving a robot a direct feed to its emotional core. Always ensure you're precisely targeting the intended records and have a solid recovery plan.
s
@Marvin i have sqllite, prefect has some CLI commands to clean database?
m
Prefect doesn't have specific CLI commands to clean or reset the SQLite database directly. However, you can achieve this by manually executing commands or using some practices to handle the cleanup: 1. Use SQLite CLI Commands: You can use SQLite command-line interface to remove records or reset specific tables. Here’s a basic outline: - Open your SQLite database using a tool like the SQLite command line or a GUI tool like DB Browser for SQLite. - Execute SQL commands to delete the rows you want to clear. For example:
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sql
     DELETE FROM flow_runs WHERE state = 'Running';
- Make sure to replace 
flow_runs
and 
state
with actual table names and conditions you want to target in your database schema. 2. Backup Before Clean: Always create a backup of your database before performing any delete operations to prevent accidental loss of important data. 3. Automate Cleanup Tasks: Consider creating a script that uses Python's 
sqlite3
module to automate these cleanup operations. This can be run as a scheduled task to ensure your database remains clear of redundant or stale records. 4. Database Migrations: Prefect uses Alembic for database migrations with SQLAlchemy, but this is typically for schema changes rather than content cleaning. If your database needs to be reset frequently, consider adjusting your workflow to avoid such states, if feasible. 5. Considerations: If you're self-hosting Prefect with SQLite, remember that it's more suitable for development and testing. For production environments, it's recommended to use a more robust database like PostgreSQL. If you encounter any issues, Prefect's community resources may provide additional insights, or consider exploring Prefect's documentation on managing the database for more guidance.
s
@Marvin when prefect server was starting, working pool already works, idk why. Need to off in Prefect UI, after worker can start. I think it will be useful
m
It sounds like your work pool might be set to automatically start when the Prefect server is booting up. This automatic behavior can sometimes preempt the starting of individual workers if resources are constrained or settings are not aligned. Here are some steps and considerations to help manage this: 1. Prefect UI Dashboard: - You can manage and control your work pools and workers directly from the Prefect UI. This manual intervention ensures that you can start and stop operations as needed. - If you find that the pool always starts when it's not supposed to, try setting it to "stopped" or disabling auto-activation (if applicable) directly from the UI or through the Prefect settings. 2. Configuration Files and Environment Variables: - Check your Prefect configuration files or environment variables to ensure there's no setting that causes work pools to auto-start on server boot. Sometimes automated scripts or persistent settings can invoke certain behaviors by default. 3. Server Initialization Scripts: - If you have any scripts or cron jobs that execute when the server starts, verify that they do not contain commands to automatically spin up your work pools. 4. Feedback and Feature Suggestions: - Since you mentioned it would be useful to have a more controlled way to manage these settings from the Prefect UI, consider providing feedback to the Prefect team. They might offer insights or consider feature requests to make such configurations more intuitive. If managing via the UI seems cumbersome as a regular task, scripting the process using Prefect's API could streamline operations instead of manual intervention through the UI every time the server starts. Additionally, if you experience recurring issues, the Prefect community is a great resource to discuss potential solutions or workarounds.
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