Add option to flush database before/after tests

We need to flush database after running tests.
Before py.test with parallel tests was introduced
dropdb was performed by ./run_tests.sh, but currently
we need to run dropdb for each slave

- Added py.test --cleandb
- Connection should be closed and returned to pool,
  and pool should be recreated, because we are reusing
  same engine after db cleanup is done
- We should not reuse metadata used for models declaration,
  it gets populated by stale db information

DocImpact
Closes-Bug: 1396500
Change-Id: Idc2d4d6395b8b5f30dc7f5e72a80b830808d2b75

nailgun/conftest.py

@@ -22,6 +22,8 @@ from nailgun.settings import settings
 def pytest_addoption(parser):
     parser.addoption("--dbname", default=settings.DATABASE['name'],
                      help="Overwrite database name")
+    parser.addoption("--cleandb", default=False, action="store_true",
+                     help="Provide this flag to dropdb/syncdb for all slaves")
 
 
 def pytest_configure(config):
@@ -39,6 +41,18 @@ def pytest_configure(config):
         if not_present(cursor, db_name):
             create_database(connection, cursor, db_name)
     settings.DATABASE['name'] = db_name
+    cleandb = config.getoption('cleandb')
+    if cleandb:
+        from nailgun.db import dropdb, syncdb
+        dropdb()
+        syncdb()
+
+
+def pytest_unconfigure(config):
+    cleandb = config.getoption('cleandb')
+    if cleandb:
+        from nailgun.db import dropdb
+        dropdb()
 
 
 def create_database(connection, cursor, name):

nailgun/nailgun/db/sqlalchemy/__init__.py

@@ -19,6 +19,7 @@ import contextlib
 from sqlalchemy import create_engine
 from sqlalchemy import schema
 
+from sqlalchemy import MetaData
 from sqlalchemy.engine import reflection
 from sqlalchemy.orm import scoped_session
 from sqlalchemy.orm import Session
@@ -96,11 +97,10 @@ def syncdb():
 
 def dropdb():
     from nailgun.db import migration
-    from nailgun.db.sqlalchemy.models.base import Base
-
     conn = engine.connect()
     trans = conn.begin()
-
+    meta = MetaData()
+    meta.reflect(bind=engine)
     inspector = reflection.Inspector.from_engine(engine)
 
     tbs = []
@@ -116,7 +116,7 @@ def dropdb():
             )
         t = schema.Table(
             table_name,
-            Base.metadata,
+            meta,
             *fks,
             extend_existing=True
         )
@@ -142,10 +142,10 @@ def dropdb():
 
     for tp in custom_types:
         conn.execute("DROP TYPE {0}".format(tp[1]))
-
     trans.commit()
     migration.drop_migration_meta(engine)
-
+    conn.close()
+    engine.dispose()
 
 def flush():
     """Delete all data from all tables within nailgun metadata

run_tests.sh

@@ -247,7 +247,7 @@ function run_nailgun_tests {
   local result=0
   local artifacts=$ARTIFACTS/nailgun
   local config=$artifacts/test.yaml
-  local options="-vv --junit-xml $NAILGUN_XUNIT"
+  local options="-vv --cleandb --junit-xml $NAILGUN_XUNIT"
   prepare_artifacts $artifacts $config
   if [ $# -ne 0 ]; then
     TESTS="$@"
@@ -256,9 +256,6 @@ function run_nailgun_tests {
   if [ ! $TEST_WORKERS -eq 0 ]; then
     options+=" -n $TEST_WORKERS"
   fi
-  # prepare database
-  dropdb $config
-  syncdb $config false
 
   pushd $ROOT/nailgun >> /dev/null
   # # run tests