Split loading config vs homeserver setup (#18933)

This allows us to get access to `server_name` so we can use it when
creating the `LoggingContext("main")` in the future (pre-requisite for
#18868).

This also allows us more flexibility to parse config however we want and
setup a Synapse homeserver. Like what we do in [Synapse Pro for Small
Hosts](https://github.com/element-hq/synapse-small-hosts).

Split out from #18868

Author: MadLittleMods

changelog.d/18933.misc

@@ -0,0 +1 @@
+Split loading config from homeserver `setup`.

synapse/app/admin_cmd.py

@@ -24,7 +24,7 @@
 import os
 import sys
 import tempfile
-from typing import List, Mapping, Optional, Sequence
+from typing import List, Mapping, Optional, Sequence, Tuple
 
 from twisted.internet import defer, task
 
@@ -256,7 +256,7 @@ def finished(self) -> str:
         return self.base_directory
 
 
-def start(config_options: List[str]) -> None:
+def load_config(argv_options: List[str]) -> Tuple[HomeServerConfig, argparse.Namespace]:
     parser = argparse.ArgumentParser(description="Synapse Admin Command")
     HomeServerConfig.add_arguments_to_parser(parser)
 
@@ -282,11 +282,15 @@ def start(config_options: List[str]) -> None:
     export_data_parser.set_defaults(func=export_data_command)
 
     try:
-        config, args = HomeServerConfig.load_config_with_parser(parser, config_options)
+        config, args = HomeServerConfig.load_config_with_parser(parser, argv_options)
     except ConfigError as e:
         sys.stderr.write("\n" + str(e) + "\n")
         sys.exit(1)
 
+    return config, args
+
+
+def start(config: HomeServerConfig, args: argparse.Namespace) -> None:
     if config.worker.worker_app is not None:
         assert config.worker.worker_app == "synapse.app.admin_cmd"
 
@@ -325,7 +329,7 @@ def start(config_options: List[str]) -> None:
     # command.
 
     async def run() -> None:
-        with LoggingContext("command"):
+        with LoggingContext(name="command"):
             await _base.start(ss)
             await args.func(ss, args)
 
@@ -337,5 +341,6 @@ async def run() -> None:
 
 
 if __name__ == "__main__":
-    with LoggingContext("main"):
-        start(sys.argv[1:])
+    homeserver_config, args = load_config(sys.argv[1:])
+    with LoggingContext(name="main"):
+        start(homeserver_config, args)

synapse/app/appservice.py

@@ -21,13 +21,14 @@
 
 import sys
 
-from synapse.app.generic_worker import start
+from synapse.app.generic_worker import load_config, start
 from synapse.util.logcontext import LoggingContext
 
 
 def main() -> None:
-    with LoggingContext("main"):
-        start(sys.argv[1:])
+    homeserver_config = load_config(sys.argv[1:])
+    with LoggingContext(name="main"):
+        start(homeserver_config)
 
 
 if __name__ == "__main__":

synapse/app/client_reader.py

@@ -21,13 +21,14 @@
 
 import sys
 
-from synapse.app.generic_worker import start
+from synapse.app.generic_worker import load_config, start
 from synapse.util.logcontext import LoggingContext
 
 
 def main() -> None:
-    with LoggingContext("main"):
-        start(sys.argv[1:])
+    homeserver_config = load_config(sys.argv[1:])
+    with LoggingContext(name="main"):
+        start(homeserver_config)
 
 
 if __name__ == "__main__":

synapse/app/event_creator.py

@@ -20,13 +20,14 @@
 
 import sys
 
-from synapse.app.generic_worker import start
+from synapse.app.generic_worker import load_config, start
 from synapse.util.logcontext import LoggingContext
 
 
 def main() -> None:
-    with LoggingContext("main"):
-        start(sys.argv[1:])
+    homeserver_config = load_config(sys.argv[1:])
+    with LoggingContext(name="main"):
+        start(homeserver_config)
 
 
 if __name__ == "__main__":

synapse/app/federation_reader.py

@@ -21,13 +21,14 @@
 
 import sys
 
-from synapse.app.generic_worker import start
+from synapse.app.generic_worker import load_config, start
 from synapse.util.logcontext import LoggingContext
 
 
 def main() -> None:
-    with LoggingContext("main"):
-        start(sys.argv[1:])
+    homeserver_config = load_config(sys.argv[1:])
+    with LoggingContext(name="main"):
+        start(homeserver_config)
 
 
 if __name__ == "__main__":

synapse/app/federation_sender.py

@@ -21,13 +21,14 @@
 
 import sys
 
-from synapse.app.generic_worker import start
+from synapse.app.generic_worker import load_config, start
 from synapse.util.logcontext import LoggingContext
 
 
 def main() -> None:
-    with LoggingContext("main"):
-        start(sys.argv[1:])
+    homeserver_config = load_config(sys.argv[1:])
+    with LoggingContext(name="main"):
+        start(homeserver_config)
 
 
 if __name__ == "__main__":

synapse/app/frontend_proxy.py

@@ -21,13 +21,14 @@
 
 import sys
 
-from synapse.app.generic_worker import start
+from synapse.app.generic_worker import load_config, start
 from synapse.util.logcontext import LoggingContext
 
 
 def main() -> None:
-    with LoggingContext("main"):
-        start(sys.argv[1:])
+    homeserver_config = load_config(sys.argv[1:])
+    with LoggingContext(name="main"):
+        start(homeserver_config)
 
 
 if __name__ == "__main__":

synapse/app/generic_worker.py

@@ -310,13 +310,26 @@ def start_listening(self) -> None:
         self.get_replication_command_handler().start_replication(self)
 
 
-def start(config_options: List[str]) -> None:
+def load_config(argv_options: List[str]) -> HomeServerConfig:
+    """
+    Parse the commandline and config files (does not generate config)
+
+    Args:
+        argv_options: The options passed to Synapse. Usually `sys.argv[1:]`.
+
+    Returns:
+        Config object.
+    """
     try:
-        config = HomeServerConfig.load_config("Synapse worker", config_options)
+        config = HomeServerConfig.load_config("Synapse worker", argv_options)
     except ConfigError as e:
         sys.stderr.write("\n" + str(e) + "\n")
         sys.exit(1)
 
+    return config
+
+
+def start(config: HomeServerConfig) -> None:
     # For backwards compatibility let any of the old app names.
     assert config.worker.worker_app in (
         "synapse.app.appservice",
@@ -368,8 +381,9 @@ async def start() -> None:
 
 
 def main() -> None:
-    with LoggingContext("main"):
-        start(sys.argv[1:])
+    homeserver_config = load_config(sys.argv[1:])
+    with LoggingContext(name="main"):
+        start(homeserver_config)
 
 
 if __name__ == "__main__":

synapse/app/homeserver.py

@@ -308,17 +308,21 @@ def start_listening(self) -> None:
                 logger.warning("Unrecognized listener type: %s", listener.type)
 
 
-def setup(config_options: List[str]) -> SynapseHomeServer:
+def load_or_generate_config(argv_options: List[str]) -> HomeServerConfig:
     """
+    Parse the commandline and config files
+
+    Supports generation of config files, so is used for the main homeserver app.
+
     Args:
-        config_options_options: The options passed to Synapse. Usually `sys.argv[1:]`.
+        argv_options: The options passed to Synapse. Usually `sys.argv[1:]`.
 
     Returns:
         A homeserver instance.
     """
     try:
         config = HomeServerConfig.load_or_generate_config(
-            "Synapse Homeserver", config_options
+            "Synapse Homeserver", argv_options
         )
     except ConfigError as e:
         sys.stderr.write("\n")
@@ -332,6 +336,20 @@ def setup(config_options: List[str]) -> SynapseHomeServer:
         # generating config files and shouldn't try to continue.
         sys.exit(0)
 
+    return config
+
+
+def setup(config: HomeServerConfig) -> SynapseHomeServer:
+    """
+    Create and setup a Synapse homeserver instance given a configuration.
+
+    Args:
+        config: The configuration for the homeserver.
+
+    Returns:
+        A homeserver instance.
+    """
+
     if config.worker.worker_app:
         raise ConfigError(
             "You have specified `worker_app` in the config but are attempting to start a non-worker "
@@ -405,10 +423,12 @@ def run(hs: HomeServer) -> None:
 
 
 def main() -> None:
+    homeserver_config = load_or_generate_config(sys.argv[1:])
+
     with LoggingContext("main"):
         # check base requirements
         check_requirements()
-        hs = setup(sys.argv[1:])
+        hs = setup(homeserver_config)
 
         # redirect stdio to the logs, if configured.
         if not hs.config.logging.no_redirect_stdio: