Core & Internals: reduce usage of global temp table detection. rucio#…

…5714

Use memcached instead of a local cache.
Make it configurable to allow completely avoid any DB call.

lib/rucio/common/cache.py

@@ -39,7 +39,7 @@
         _mc_client.close()
 
 
-def make_region_memcached(expiration_time, function_key_generator=None):
+def make_region_memcached(expiration_time, function_key_generator=None, memcached_expire_time=None):
     """
     Make and configure a dogpile.cache.pymemcache region
     """
@@ -55,7 +55,7 @@ def make_region_memcached(expiration_time, function_key_generator=None):
             arguments={
                 'url': CACHE_URL,
                 'distributed_lock': True,
-                'memcached_expire_time': expiration_time + 60,  # must be bigger than expiration_time
+                'memcached_expire_time': memcached_expire_time if memcached_expire_time else expiration_time + 60,  # must be bigger than expiration_time
             }
         )
     else:

lib/rucio/db/sqla/util.py

@@ -22,7 +22,6 @@
 import sqlalchemy
 from alembic import command, op
 from alembic.config import Config
-from dogpile.cache import make_region
 from dogpile.cache.api import NoValue
 from sqlalchemy import func, inspect, Column, PrimaryKeyConstraint
 from sqlalchemy.dialects.postgresql.base import PGInspector
@@ -33,7 +32,8 @@
 from sqlalchemy.sql.expression import select, text
 
 from rucio import alembicrevision
-from rucio.common.config import config_get
+from rucio.common.cache import make_region_memcached
+from rucio.common.config import config_get, config_get_list
 from rucio.common.schema import get_schema_value
 from rucio.common.types import InternalAccount
 from rucio.common.utils import generate_uuid
@@ -48,7 +48,7 @@
     from sqlalchemy.orm import Session  # noqa: F401
     from sqlalchemy.engine import Inspector  # noqa: F401
 
-REGION = make_region().configure('dogpile.cache.memory', expiration_time=600)
+REGION = make_region_memcached(expiration_time=600, memcached_expire_time=3660)
 
 
 def build_database():
@@ -309,8 +309,13 @@ def list_oracle_global_temp_tables(session):
     """
     Retrieve the list of global temporary tables in oracle
     """
+    global_temp_tables = config_get_list('core', 'oracle_global_temp_tables', raise_exception=False, check_config_table=False, default=[])
+    if global_temp_tables:
+        return [t.upper() for t in global_temp_tables]
+
     cache_key = 'oracle_global_temp_tables'
-    global_temp_tables = REGION.get(cache_key)
+    # Set long expiration time to avoid hammering the database with this costly query
+    global_temp_tables = REGION.get(cache_key, expiration_time=3600)
     if isinstance(global_temp_tables, NoValue):
         # As of time of writing, get_temp_table_names doesn't allow setting the correct schema when called
         # (like get_table_names allows). This may be fixed in a later version of sqlalchemy: