nchan_store_init_worker: Assertion `procslot_found == 1' failed

The error message you’re encountering suggests an issue related to the Nchan module in Nginx. It seems like the Nchan module is trying to initialize a shared memory zone called “memstore,” and it’s encountering a problem with it.

This issue might be related to the fact that you initially had Passenger for Ruby on Rails support and then removed it.

You can try the following steps:

• Check Nginx Configuration Files: Ensure that there are no remnants of the Passenger configuration in your Nginx configuration files. Specifically, look for any references to Passenger and remove them. You may have configuration files in /etc/nginx/conf.d/ or /etc/nginx/sites-enabled/. Make sure your Nginx configuration is clean and does not reference Passenger anymore.

• Check for Nchan Module: Since the error message mentions the Nchan module, make sure you have uninstalled the Nchan module properly if it’s no longer needed. You can check whether it’s installed using nginx -V to list the compiled-in modules. If it’s still compiled into Nginx, you may need to recompile Nginx without the Nchan module.

• Check Nginx Logs: Review the Nginx error logs (usually located in /var/log/nginx/error.log) for more detailed error messages. This might provide more information about what’s causing the crash.

• Update Nginx: Consider updating Nginx to the latest version. Ubuntu 16.04 may have an older version of Nginx, and updating it might resolve some known issues. However, be cautious with this step, as updating Nginx may require changes to your configuration files.

• Check for Resource Issues: Ensure that your server has enough resources (CPU, memory, disk space). Resource limitations can sometimes cause unexpected crashes.

• Check for Third-party Modules: If you’re using third-party modules or extensions with Nginx, make sure they are compatible with your Nginx version and that they are correctly configured.

• Consider Using a More Recent Ubuntu Version: Ubuntu 16.04 LTS reached its end of life in April 2021. Consider upgrading to a more recent LTS version (e.g., Ubuntu 20.04 LTS) to benefit from security updates and improved software compatibility.

• Monitor Your Server: Implement server monitoring and automated alerting to detect and respond to server issues more proactively. Tools like Nagios, Zabbix, or Prometheus can help with this.

• Consider Professional Support: If you continue to experience issues and are unable to resolve them, it may be worthwhile to seek professional support, especially given the importance of your server for your website’s reputation.

Remember to backup your Nginx configuration files before making any changes, and proceed with caution, especially if your server is in a production environment.