Enable connection pooling in the registry

conf/init/service/gunicorn_registry/run

@@ -4,6 +4,7 @@ echo 'Starting gunicon'
 
 QUAYPATH=${QUAYPATH:-"."}
 QUAYCONF=${QUAYCONF:-"$QUAYPATH/conf"}
+DB_CONNECTION_POOLING=${DB_CONNECTION_POOLING:-"true"}
 
 cd ${QUAYDIR:-"/"}
 PYTHONPATH=$QUAYPATH nice -n 10 venv/bin/gunicorn -c $QUAYCONF/gunicorn_registry.py registry:application

data/database.py

@@ -6,9 +6,10 @@ import string
 import sys
 import time
 import uuid
+import os
 
 from contextlib import contextmanager
-from collections import defaultdict
+from collections import defaultdict, namedtuple
 from datetime import datetime
 from random import SystemRandom
 
@@ -17,6 +18,7 @@ import toposort
 from enum import Enum
 from peewee import *
 from playhouse.shortcuts import RetryOperationalError
+from playhouse.pool import PooledMySQLDatabase, PooledPostgresqlDatabase, PooledSqliteDatabase
 
 from sqlalchemy.engine.url import make_url
 
@@ -39,13 +41,14 @@ DEFAULT_DB_CONNECT_TIMEOUT = 10 # seconds
 # image has not yet been scanned.
 IMAGE_NOT_SCANNED_ENGINE_VERSION = -1
 
+schemedriver = namedtuple('schemedriver', ['driver', 'pooled_driver'])
 
 _SCHEME_DRIVERS = {
-  'mysql': MySQLDatabase,
-  'mysql+pymysql': MySQLDatabase,
-  'sqlite': SqliteDatabase,
-  'postgresql': PostgresqlDatabase,
-  'postgresql+psycopg2': PostgresqlDatabase,
+  'mysql': schemedriver(MySQLDatabase, PooledMySQLDatabase),
+  'mysql+pymysql': schemedriver(MySQLDatabase, PooledMySQLDatabase),
+  'sqlite': schemedriver(SqliteDatabase, PooledSqliteDatabase),
+  'postgresql': schemedriver(PostgresqlDatabase, PooledPostgresqlDatabase),
+  'postgresql+psycopg2': schemedriver(PostgresqlDatabase, PooledPostgresqlDatabase),
 }
 
 
@@ -269,7 +272,12 @@ def _db_from_url(url, db_kwargs, connect_timeout=DEFAULT_DB_CONNECT_TIMEOUT):
   if parsed_url.drivername != 'sqlite':
     db_kwargs['connect_timeout'] = db_kwargs.get('connect_timeout', connect_timeout)
 
-  driver = _SCHEME_DRIVERS[parsed_url.drivername]
+  drivers = _SCHEME_DRIVERS[parsed_url.drivername]
+  driver = drivers.driver
+  if os.getenv('DB_CONNECTION_POOLING', 'false').lower() == 'true':
+    logger.debug('Connection pooling enabled')
+    driver = drivers.pooled_driver
+
   wrapped_driver = _wrap_for_retry(driver)
   return wrapped_driver(parsed_url.database, **db_kwargs)