Ah, this is actually a common situation during migrations from Prefect 2.x to 3.x. There are several key reasons this might happen, and fortunately, there are specific solutions for each: 1. Infrastructure Resources - Prefect 3.x has different resource requirements than 2.x. Given that you're using a db.t4g.small instance, you'll want to ensure it has sufficient resources for the new architecture. - Monitor your database and worker logs for any signs of resource constraints or timeout issues. 2. Worker Configuration - In Prefect 3.x, workers replace the old agent system. If workers aren't properly configured or are experiencing issues, flows can appear to hang in the "Running" state. - Ensure your workers are properly running and configured with appropriate work pools. - Check worker logs for any error messages or warnings. 3. Flow Execution Environment - Prefect 3.x handles flow execution differently. Make sure your deployment infrastructure (containers, virtual environments, etc.) is properly configured. - Use logging to debug:

python
     from prefect import get_run_logger

     @flow
     def my_flow():
         logger = get_run_logger()
         <http://logger.info|logger.info>("Flow starting...")
         # Your flow code
         <http://logger.info|logger.info>("Flow completed")

4. State Handling - Prefect 3.x has a more robust state transition system. Sometimes flows appear "stuck" because they're actually failing silently or timing out. - Set appropriate timeouts in your deployments - Monitor flow run logs in the UI or via CLI for detailed state transition information To troubleshoot: 1. Check your worker logs for any errors 2. Verify resource utilization on your db.t4g.small instance 3. Ensure all dependencies are properly installed in your flow's execution environment 4. Consider implementing more detailed logging in your flows 5. Check that your work pool and worker configurations match your deployment needs For more detailed information, you can refer to: - Prefect 3.x States Documentation - Troubleshooting Guide - Server Configuration Guide Would you like me to dive deeper into any of these specific areas or help you implement any of these solutions?

Based on your setup using a db.t4g.small instance, database resource constraints are the most likely culprit. Here's why: 1. The db.t4g.small instance type has limited CPU credits and memory (2GB RAM), which can be quickly exhausted in Prefect 3.x because: - It handles state transitions more frequently - It maintains more detailed logging - It manages concurrent operations differently than 2.x The symptoms typically manifest as: - Flow runs appearing to hang without error messages - Delayed state updates in the UI - Inconsistent behavior during peak load periods You can verify this is your issue by: 1. Checking your RDS metrics in AWS CloudWatch, particularly: - CPU Credit Balance - Free Memory - Database Connections 2. Looking for slow query logs in your database 3. Monitoring if the issues occur more frequently during periods of higher flow run concurrency The most straightforward solution would be to upgrade to at least a db.t4g.medium instance, which provides double the memory and CPU credits. If that's not immediately possible, you can: 1. Reduce the number of concurrent flow runs 2. Implement more aggressive database connection pooling 3. Add appropriate indexing to your Prefect database tables Would you like me to provide specific guidance for any of these solutions?

Sigh... No, this information isn't as prominently featured in the migration documentation as it should be. While the migration guides do cover technical steps and architectural changes, they don't adequately highlight the increased database resource requirements when moving from 2.x to 3.x. The documentation does mention: - Database migration timeout considerations - The need to set

PREFECT_API_DATABASE_TIMEOUT

for larger databases - General architectural changes But it doesn't explicitly warn about: - The need for potentially larger database instances - Specific instance size recommendations - Performance implications of smaller database instances like db.t4g.small This is a rather significant oversight, particularly for users managing self-hosted Prefect instances. The documentation focuses more on the functional aspects of migration rather than the operational requirements. If you're interested in helping the community, you might consider: 1. Opening a documentation improvement issue on GitHub 2. Sharing your experience on the Prefect Discourse forum 3. Contributing to the migration guide documentation Would you like me to help you draft a documentation improvement suggestion based on your experience?

Here's a draft for a GitHub issue that addresses this documentation gap:

markdown
Title: Documentation: Add Database Resource Requirements to Migration Guide

## Overview
When migrating from Prefect 2.x to 3.x, users need clear guidance about database resource requirements. Currently, this critical information is not prominently featured in the migration documentation, leading to potential performance issues and hanging flow runs.

## Current State
The migration guide currently covers:
- Technical steps for migration
- Architectural changes
- Database timeout settings (`PREFECT_API_DATABASE_TIMEOUT`)

## Proposed Additions

### 1. Database Requirements Section
Add a new section titled "Database Requirements and Sizing" that includes:

#### Resource Requirements
- Minimum recommended database specifications
- Comparison of resource usage between 2.x and 3.x
- Warning about common instance types that may be insufficient (e.g., db.t4g.small)

#### Common Symptoms of Undersized Databases
- Flow runs appearing to hang in "Running" state
- Delayed state transitions
- Inconsistent UI updates
- Database timeout errors

#### Recommended Specifications
- Development: Minimum specifications for development/testing
- Production: Recommended specifications based on workflow volume
  - Small deployments (<100 flows/day)
  - Medium deployments (100-1000 flows/day)
  - Large deployments (>1000 flows/day)

### 2. Troubleshooting Guide
Add a subsection specifically for database-related issues:
- How to identify database resource constraints
- Monitoring metrics to watch
- Steps to upgrade database resources
- Temporary workarounds for resource constraints

## Why This Matters
This addition will:
1. Help users plan migrations more effectively
2. Reduce support issues related to database sizing
3. Improve user experience during migration
4. Prevent common performance issues

## Personal Experience
As a user who migrated from 2.x to 3.x using a db.t4g.small instance, I encountered hanging flow runs due to insufficient database resources. This issue could have been avoided with clearer documentation about resource requirements.

## Additional Context
This information would be valuable in:
- Migration guide
- Self-hosted deployment guide
- Production deployment best practices

Would you like me to help implement this documentation improvement?

This draft: 1. Clearly outlines the current documentation gap 2. Provides a structured solution 3. Includes real-world context from your experience 4. Maintains a constructive tone 5. Offers specific, actionable improvements Would you like me to modify any part of this draft before you submit it? For instance, we could add more specific details about your experience with the db.t4g.small instance or include additional sections you think would be helpful.