Add database config class (#6513)

This encapsulates config for a given database and is the way to get new
connections.

synapse/server.py

@@ -25,7 +25,6 @@ import abc
 import logging
 import os
 
-from twisted.enterprise import adbapi
 from twisted.mail.smtp import sendmail
 from twisted.web.client import BrowserLikePolicyForHTTPS
 
@@ -98,7 +97,6 @@ from synapse.server_notices.worker_server_notices_sender import (
 )
 from synapse.state import StateHandler, StateResolutionHandler
 from synapse.storage import DataStores, Storage
-from synapse.storage.engines import create_engine
 from synapse.streams.events import EventSources
 from synapse.util import Clock
 from synapse.util.distributor import Distributor
@@ -134,7 +132,6 @@ class HomeServer(object):
 
     DEPENDENCIES = [
         "http_client",
-        "db_pool",
         "federation_client",
         "federation_server",
         "handlers",
@@ -233,12 +230,6 @@ class HomeServer(object):
         self.admin_redaction_ratelimiter = Ratelimiter()
         self.registration_ratelimiter = Ratelimiter()
 
-        self.database_engine = create_engine(config.database_config)
-        config.database_config.setdefault("args", {})[
-            "cp_openfun"
-        ] = self.database_engine.on_new_connection
-        self.db_config = config.database_config
-
         self.datastores = None
 
         # Other kwargs are explicit dependencies
@@ -247,10 +238,8 @@ class HomeServer(object):
 
     def setup(self):
         logger.info("Setting up.")
-        with self.get_db_conn() as conn:
-            self.datastores = DataStores(self.DATASTORE_CLASS, conn, self)
-            conn.commit()
         self.start_time = int(self.get_clock().time())
+        self.datastores = DataStores(self.DATASTORE_CLASS, self)
         logger.info("Finished setting up.")
 
     def setup_master(self):
@@ -284,6 +273,9 @@ class HomeServer(object):
     def get_datastore(self):
         return self.datastores.main
 
+    def get_datastores(self):
+        return self.datastores
+
     def get_config(self):
         return self.config
 
@@ -433,31 +425,6 @@ class HomeServer(object):
         )
         return MatrixFederationHttpClient(self, tls_client_options_factory)
 
-    def build_db_pool(self):
-        name = self.db_config["name"]
-
-        return adbapi.ConnectionPool(
-            name, cp_reactor=self.get_reactor(), **self.db_config.get("args", {})
-        )
-
-    def get_db_conn(self, run_new_connection=True):
-        """Makes a new connection to the database, skipping the db pool
-
-        Returns:
-            Connection: a connection object implementing the PEP-249 spec
-        """
-        # Any param beginning with cp_ is a parameter for adbapi, and should
-        # not be passed to the database engine.
-        db_params = {
-            k: v
-            for k, v in self.db_config.get("args", {}).items()
-            if not k.startswith("cp_")
-        }
-        db_conn = self.database_engine.module.connect(**db_params)
-        if run_new_connection:
-            self.database_engine.on_new_connection(db_conn)
-        return db_conn
-
     def build_media_repository_resource(self):
         # build the media repo resource. This indirects through the HomeServer
         # to ensure that we only have a single instance of