Add CI for synapse_port_db (#6140)

This adds:

* a test sqlite database
* a configuration file for the sqlite database
* a configuration file for a postgresql database (using the credentials in `.buildkite/docker-compose.pyXX.pgXX.yaml`)

as well as a new script named `.buildkite/scripts/test_synapse_port_db.sh` that:

1. installs Synapse
2. updates the test sqlite database to the latest schema and runs background updates on it
3. creates an empty postgresql database
4. run the `synapse_port_db` script to migrate the test sqlite database to the empty postgresql database (with coverage)

Step `2` is done via a new script located at `scripts-dev/update_database`.

The test sqlite database is extracted from a SyTest run, so that it can be considered as an actual homeserver's database with actual data in it.

7 files changed, 196 insertions, 3 deletions

diff --git a/.buildkite/postgres-config.yaml b/.buildkite/postgres-config.yaml
new file mode 100644
index 0000000000..23db43fac9
--- /dev/null
+++ b/.buildkite/postgres-config.yaml
@@ -0,0 +1,19 @@
+# Configuration file used for testing the 'synapse_port_db' script.
+# Tells the script to connect to the postgresql database that will be available in the
+# CI's Docker setup at the point where this file is considered.
+server_name: "test"
+
+report_stats: false
+
+database:
+  name: "psycopg2"
+  args:
+    user: postgres
+    host: postgres
+    password: postgres
+    database: synapse
+
+# Suppress the key server warning.
+trusted_key_servers:
+  - server_name: "matrix.org"
+suppress_key_server_warning: true
diff --git a/.buildkite/scripts/test_synapse_port_db.sh b/.buildkite/scripts/test_synapse_port_db.sh
new file mode 100755
index 0000000000..7defd47bc6
--- /dev/null
+++ b/.buildkite/scripts/test_synapse_port_db.sh
@@ -0,0 +1,29 @@
+#!/bin/bash
+#
+# Test script for 'synapse_port_db', which creates a virtualenv, installs Synapse along
+# with additional dependencies needed for the test (such as coverage or the PostgreSQL
+# driver), update the schema of the test SQLite database and run background updates on it,
+# create an empty test database in PostgreSQL, then run the 'synapse_port_db' script to
+# test porting the SQLite database to the PostgreSQL database (with coverage).
+
+set -xe
+cd `dirname $0`/../..
+
+# Create a virtualenv and use it.
+virtualenv env
+source env/bin/activate
+
+# Install dependencies for this test.
+pip install psycopg2 coverage coverage-enable-subprocess
+
+# Install Synapse itself. This won't update any libraries.
+pip install -e .
+
+# Make sure the SQLite3 database is using the latest schema and has no pending background update.
+scripts-dev/update_database --database-config .buildkite/sqlite-config.yaml
+
+# Create the PostgreSQL database.
+PGPASSWORD=postgres createdb -h postgres -U postgres synapse
+
+# Run the script
+coverage run scripts/synapse_port_db --sqlite-database .buildkite/test_db.db --postgres-config .buildkite/postgres-config.yaml
diff --git a/.buildkite/sqlite-config.yaml b/.buildkite/sqlite-config.yaml
new file mode 100644
index 0000000000..56503cc4ce
--- /dev/null
+++ b/.buildkite/sqlite-config.yaml
@@ -0,0 +1,16 @@
+# Configuration file used for testing the 'synapse_port_db' script.
+# Tells the 'update_database' script to connect to the test SQLite database to upgrade its
+# schema and run background updates on it.
+server_name: "test"
+
+report_stats: false
+
+database:
+  name: "sqlite3"
+  args:
+    database: ".buildkite/test_db.db"
+
+# Suppress the key server warning.
+trusted_key_servers:
+  - server_name: "matrix.org"
+suppress_key_server_warning: true
diff --git a/.buildkite/test_db.db b/.buildkite/test_db.db
new file mode 100644
index 0000000000..f20567ba73
--- /dev/null
+++ b/.buildkite/test_db.db
Binary files differdiff --git a/changelog.d/6140.misc b/changelog.d/6140.misc
new file mode 100644
index 0000000000..0feb97ec61
--- /dev/null
+++ b/changelog.d/6140.misc
@@ -0,0 +1 @@
+Add a CI job to test the `synapse_port_db` script.
\ No newline at end of file
diff --git a/scripts-dev/update_database b/scripts-dev/update_database
new file mode 100755
index 0000000000..10166583e1
--- /dev/null
+++ b/scripts-dev/update_database
@@ -0,0 +1,125 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright 2019 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse
+import logging
+import sys
+
+import yaml
+
+from twisted.internet import defer, reactor
+
+from synapse.config.homeserver import HomeServerConfig
+from synapse.metrics.background_process_metrics import run_as_background_process
+from synapse.server import HomeServer
+from synapse.storage.engines import create_engine
+from synapse.storage import DataStore
+from synapse.storage.prepare_database import prepare_database
+
+logger = logging.getLogger("update_database")
+
+
+class MockHomeserver(HomeServer):
+    DATASTORE_CLASS = DataStore
+
+    def __init__(self, config, database_engine, db_conn, **kwargs):
+        super(MockHomeserver, self).__init__(
+            config.server_name,
+            reactor=reactor,
+            config=config,
+            database_engine=database_engine,
+            **kwargs
+        )
+
+        self.database_engine = database_engine
+        self.db_conn = db_conn
+
+    def get_db_conn(self):
+        return self.db_conn
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        description=(
+            "Updates a synapse database to the latest schema and runs background updates"
+            " on it."
+        )
+    )
+    parser.add_argument("-v", action='store_true')
+    parser.add_argument(
+        "--database-config",
+        type=argparse.FileType('r'),
+        required=True,
+        help="A database config file for either a SQLite3 database or a PostgreSQL one.",
+    )
+
+    args = parser.parse_args()
+
+    logging_config = {
+        "level": logging.DEBUG if args.v else logging.INFO,
+        "format": "%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(message)s",
+    }
+
+    logging.basicConfig(**logging_config)
+
+    # Load, process and sanity-check the config.
+    hs_config = yaml.safe_load(args.database_config)
+
+    if "database" not in hs_config:
+        sys.stderr.write("The configuration file must have a 'database' section.\n")
+        sys.exit(4)
+
+    config = HomeServerConfig()
+    config.parse_config_dict(hs_config, "", "")
+
+    # Create the database engine and a connection to it.
+    database_engine = create_engine(config.database_config)
+    db_conn = database_engine.module.connect(
+        **{
+            k: v
+            for k, v in config.database_config.get("args", {}).items()
+            if not k.startswith("cp_")
+        }
+    )
+
+    # Update the database to the latest schema.
+    prepare_database(db_conn, database_engine, config=config)
+    db_conn.commit()
+
+    # Instantiate and initialise the homeserver object.
+    hs = MockHomeserver(
+        config,
+        database_engine,
+        db_conn,
+        db_config=config.database_config,
+    )
+    # setup instantiates the store within the homeserver object.
+    hs.setup()
+    store = hs.get_datastore()
+
+    @defer.inlineCallbacks
+    def run_background_updates():
+        yield store.run_background_updates(sleep=False)
+        # Stop the reactor to exit the script once every background update is run.
+        reactor.stop()
+
+    # Apply all background updates on the database.
+    reactor.callWhenRunning(lambda: run_as_background_process(
+        "background_updates", run_background_updates
+    ))
+
+    reactor.run()
+
diff --git a/synapse/storage/background_updates.py b/synapse/storage/background_updates.py
index 80b57a948c..37d469ffd7 100644
--- a/synapse/storage/background_updates.py
+++ b/synapse/storage/background_updates.py
@@ -94,13 +94,16 @@ class BackgroundUpdateStore(SQLBaseStore):
         self._all_done = False
 
     def start_doing_background_updates(self):
-        run_as_background_process("background_updates", self._run_background_updates)
+        run_as_background_process("background_updates", self.run_background_updates)
 
     @defer.inlineCallbacks
-    def _run_background_updates(self):
+    def run_background_updates(self, sleep=True):
         logger.info("Starting background schema updates")
         while True:
-            yield self.hs.get_clock().sleep(self.BACKGROUND_UPDATE_INTERVAL_MS / 1000.0)
+            if sleep:
+                yield self.hs.get_clock().sleep(
+                    self.BACKGROUND_UPDATE_INTERVAL_MS / 1000.0
+                )
 
             try:
                 result = yield self.do_next_background_update(