How to restart CKAN processes (but not jobs/worker) inside running ckan-docker dev container?

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Summary

The problem at hand is restarting CKAN server processes inside a running ckan-docker development container without affecting the jobs/worker process or restarting the entire container. This is a common requirement during local extension development when frequent application restarts are necessary for code/config reload.

Root Cause

The root cause of this issue is the way the start_ckan_development.sh script is designed to automatically restart the CKAN server processes if they exit. This is achieved through a while loop that continuously runs the CKAN server command. The key points are:

  • The script uses a while true loop to ensure continuous execution
  • The CKAN server process is run with automatic reload
  • If the CKAN server process exits, the script restarts it after a short delay

Why This Happens in Real Systems

This issue occurs in real systems because of the following reasons:

  • Automated restart mechanisms can sometimes interfere with manual restart attempts
  • Containerization can make it difficult to manage individual processes within a container
  • Development environments often require frequent restarts, which can be challenging to manage without affecting other processes

Real-World Impact

The real-world impact of this issue includes:

  • Inability to reload code/config changes without affecting other processes
  • Difficulty in debugging due to the automated restart mechanism
  • Potential data loss if the jobs/worker process is interrupted

Example or Code

# Example of how to restart CKAN server processes without affecting jobs/worker
# Get the PID of the CKAN server process
CKAN_SERVER_PID=$(pgrep -f "ckan -c /srv/app/ckan.ini run")

# Kill the CKAN server process
kill $CKAN_SERVER_PID

# Wait for the process to exit
wait $CKAN_SERVER_PID

# Restart the CKAN server process
$CKAN_RUN $CKAN_OPTIONS

How Senior Engineers Fix It

Senior engineers fix this issue by:

  • Understanding the script logic and identifying the automated restart mechanism
  • Using process management tools like pgrep and kill to manage individual processes
  • Implementing a custom restart mechanism that allows for selective restarts without affecting other processes

Why Juniors Miss It

Junior engineers may miss this issue because:

  • Lack of experience with containerization and process management
  • Insufficient understanding of the script logic and automated restart mechanisms
  • Limited knowledge of debugging tools and techniques