retry query class

orm/_retry.py

@@ -0,0 +1,34 @@
+from sqlalchemy.exc import OperationalError, StatementError
+from sqlalchemy.orm.query import Query as _Query
+from time import sleep
+
+class RetryingQuery(_Query):
+    __max_retry_count__ = 3
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+    def __iter__(self):
+        attempts = 0
+        while True:
+            attempts += 1
+            try:
+                return super().__iter__()
+            except OperationalError as ex:
+                if "server closed the connection unexpectedly" not in str(ex):
+                    raise
+                if attempts <= self.__max_retry_count__:
+                    sleep_for = 2 ** (attempts - 1)
+                    logging.error(
+                        "/!\ Database connection error: retrying Strategy => sleeping for {}s"
+                    " and will retry (attempt #{} of {}) \n Detailed query impacted: {}".format(
+                        sleep_for, attempts, self.__max_retry_count__, ex)
+                )
+                    sleep(sleep_for)
+                    continue
+                else:
+                    raise
+            except StatementError as ex:
+                if "reconnect until invalid transaction is rolled back" not in str(ex):
+                    raise
+                self.session.rollback()

orm/base.py

@@ -6,8 +6,17 @@ from sqlalchemy.orm import sessionmaker
 from sqlalchemy.sql.schema import Table
 
 from settings import DB_URL
+from _retry import RetryingQuery
 
-engine = create_engine(DB_URL, convert_unicode=True, echo=False)
+# engine = create_engine(DB_URL, convert_unicode=True, echo=False)
+engine = sqlalchemy.create_engine(connection_string,
+                                      pool_size=10,
+                                      max_overflow=2,
+                                      pool_recycle=300,
+                                      pool_pre_ping=True,
+                                      pool_use_lifo=True)
+
+sqlalchemy.orm.sessionmaker(bind=engine, query_cls=RetryingQuery)
 Session = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 global_session = Session()