make mongo tests safer to run in parallel

pants runs each test file separately in pytest. So, if two files try to
modify the same database at the same time, we'll get strange results.
So, modify the db name to ensure that they are safe in parallel.

Author: cognifloyd

st2common/tests/unit/test_db.py

@@ -126,6 +126,7 @@ def test_check_connect(self):
     def test_network_level_compression(self):
         disconnect()
 
+        # db is not modified in this test, so this is safe to run in parallel.
         db_name = "st2"
         db_host = "localhost"
         db_port = 27017
@@ -521,6 +522,7 @@ def test_db_connect_server_selection_timeout_ssl_on_non_ssl_listener(self):
         # and propagating the error
         disconnect()
 
+        # db is not modified in this test, so this is safe to run in parallel.
         db_name = "st2"
         db_host = "localhost"
         db_port = 27017

st2tests/st2tests/config.py

@@ -85,7 +85,9 @@ def _register_config_opts():
 
 
 def _override_db_opts():
-    CONF.set_override(name="db_name", override="st2-test", group="database")
+    # use separate dbs for safer parallel test runs
+    db_name = f"st2-test{os.environ.get('ST2TESTS_PARALLEL_SLOT', '')}"
+    CONF.set_override(name="db_name", override=db_name, group="database")
     CONF.set_override(name="host", override="127.0.0.1", group="database")