Subject: Solution for RuntimeError: OrderedDict mutated during iteration in Odoo 17 CRON Jobs

I ran into the same issue on Odoo 17 on-premise. The issue lies in the registries.d being modified while being iterated over by the cron_thread method.

Initially, I thought that registries.d would only be modified upon creation, editing, or deleting of a database. However, this is not the case. The registries.d is updated more frequently, for example, when you install a new module on a database.

Upon investigating the /odoo/modules/registry.py file, I found that there are multiple threads or processes accessing and modifying the registry concurrently. 

This concurrent access can lead to the observed behavior, especially if there are background jobs or operations interacting with the registry while CRON jobs are running.

If you run CRON jobs very often, as I do, it is almost inevitable that you will encounter this error at some point. 

The solution suggested by Dries should work. It involves modifying the cron_thread method to iterate over a list copy of registries.d.items(). This prevents the iteration from being disrupted by concurrent modifications.

Here’s the change I’m going to apply:

1. Locate the cron_thread method in server.py:

   def cron_thread(self, number):
       from odoo.addons.base.models.ir_cron import ir_cron
       conn = odoo.sql_db.db_connect('postgres')
       with conn.cursor() as cr:
           pg_conn = cr._cnx
           cr.execute("SELECT pg_is_in_recovery()")
           in_recovery = cr.fetchone()[0]
           if not in_recovery:
               cr.execute("LISTEN cron_trigger")
           else:
               _logger.warning("PG cluster in recovery mode, cron trigger not activated")
           cr.commit()
   
           while True:
               select.select([pg_conn], [], [], SLEEP_INTERVAL + number)
               time.sleep(number / 100)
               pg_conn.poll()
   
               registries = odoo.modules.registry.Registry.registries
               _logger.debug('cron%d polling for jobs', number)
   
               # Create a copy of the items to avoid mutation during iteration
               for db_name, registry in list(registries.d.items()):
                   if registry.ready:
                       thread = threading.current_thread()
                       thread.start_time = time.time()
                       try:
                           ir_cron._process_jobs(db_name)
                       except Exception:
                           _logger.warning('cron%d encountered an Exception:', number, exc_info=True)
                       finally:
                           thread.start_time = None
   

2. Restart Odoo:

   sudo systemctl restart odoo
   

3. Monitor the logs to ensure the error does not reoccur and that CRON jobs are running smoothly:

   sudo tail -f /var/log/odoo/odoo-server.log
   

By making this change, I hope to prevent the OrderedDict mutated during iteration error and ensure that my CRON jobs run without interruption. 

If you encounter similar issues, this approach should help.

Best of luck!