[IMP] queue_job: HA job runner using session level advisory lock

queue_job/jobrunner/runner.py

@@ -159,12 +159,17 @@
 
 SELECT_TIMEOUT = 60
 ERROR_RECOVERY_DELAY = 5
+PG_ADVISORY_LOCK_ID = 2293787760715711918
 
 _logger = logging.getLogger(__name__)
 
 select = selectors.DefaultSelector
 
 
+class MasterElectionLost(Exception):
+    pass
+
+
 # Unfortunately, it is not possible to extend the Odoo
 # server command line arguments, so we resort to environment variables
 # to configure the runner (channels mostly).
@@ -268,6 +273,7 @@ def __init__(self, db_name):
             self.conn.set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT)
             self.has_queue_job = self._has_queue_job()
             if self.has_queue_job:
+                self._acquire_master_lock()
                 self._initialize()
         except BaseException:
             self.close()
@@ -284,6 +290,14 @@ def close(self):
             pass
         self.conn = None
 
+    def _acquire_master_lock(self):
+        """Acquire the master runner lock or raise MasterElectionLost"""
+        with closing(self.conn.cursor()) as cr:
+            cr.execute("SELECT pg_try_advisory_lock(%s)", (PG_ADVISORY_LOCK_ID,))
+            if not cr.fetchone()[0]:
+                msg = f"could not acquire master runner lock on {self.db_name}"
+                raise MasterElectionLost(msg)
+
     def _has_queue_job(self):
         with closing(self.conn.cursor()) as cr:
             cr.execute(
@@ -413,7 +427,7 @@ def get_db_names(self):
             db_names = config["db_name"].split(",")
         else:
             db_names = odoo.service.db.list_dbs(True)
-        return db_names
+        return sorted(db_names)
 
     def close_databases(self, remove_jobs=True):
         for db_name, db in self.db_by_name.items():
@@ -522,7 +536,7 @@ def run(self):
         while not self._stop:
             # outer loop does exception recovery
             try:
-                _logger.info("initializing database connections")
+                _logger.debug("initializing database connections")
                 # TODO: how to detect new databases or databases
                 #       on which queue_job is installed after server start?
                 self.initialize_databases()
@@ -537,6 +551,14 @@ def run(self):
             except InterruptedError:
                 # Interrupted system call, i.e. KeyboardInterrupt during select
                 self.stop()
+            except MasterElectionLost as e:
+                _logger.debug(
+                    "master election lost: %s, sleeping %ds and retrying",
+                    e,
+                    ERROR_RECOVERY_DELAY,
+                )
+                self.close_databases()
+                time.sleep(ERROR_RECOVERY_DELAY)
             except Exception:
                 _logger.exception(
                     "exception: sleeping %ds and retrying", ERROR_RECOVERY_DELAY