Clean up `ShardedWorkerHandlingConfig` (#9466)

* Split ShardedWorkerHandlingConfig

This is so that we have a type level understanding of when it is safe to
call `get_instance(..)` (as opposed to `should_handle(..)`).

* Remove special cases in ShardedWorkerHandlingConfig.

`ShardedWorkerHandlingConfig` tried to handle the various different ways
it was possible to configure federation senders and pushers. This led to
special cases that weren't hit during testing.

To fix this the handling of the different cases is moved from there and
`generic_worker` into the worker config class. This allows us to have
the logic in one place and allows the rest of the code to ignore the
different cases.

2 files changed, 2 insertions, 32 deletions

diff --git a/synapse/app/admin_cmd.py b/synapse/app/admin_cmd.py

index b4bd4d8e7a..9f99651aa2 100644
--- a/synapse/app/admin_cmd.py
+++ b/synapse/app/admin_cmd.py
@@ -210,7 +210,9 @@ def start(config_options):
     config.update_user_directory = False
     config.run_background_tasks = False
     config.start_pushers = False
+    config.pusher_shard_config.instances = []
     config.send_federation = False
+    config.federation_shard_config.instances = []
 
     synapse.events.USE_FROZEN_DICTS = config.use_frozen_dicts
 
diff --git a/synapse/app/generic_worker.py b/synapse/app/generic_worker.py

index 6ed405e66b..dc0d3eb725 100644
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -919,22 +919,6 @@ def start(config_options):
         # For other worker types we force this to off.
         config.appservice.notify_appservices = False
 
-    if config.worker_app == "synapse.app.pusher":
-        if config.server.start_pushers:
-            sys.stderr.write(
-                "\nThe pushers must be disabled in the main synapse process"
-                "\nbefore they can be run in a separate worker."
-                "\nPlease add ``start_pushers: false`` to the main config"
-                "\n"
-            )
-            sys.exit(1)
-
-        # Force the pushers to start since they will be disabled in the main config
-        config.server.start_pushers = True
-    else:
-        # For other worker types we force this to off.
-        config.server.start_pushers = False
-
     if config.worker_app == "synapse.app.user_dir":
         if config.server.update_user_directory:
             sys.stderr.write(
@@ -951,22 +935,6 @@ def start(config_options):
         # For other worker types we force this to off.
         config.server.update_user_directory = False
 
-    if config.worker_app == "synapse.app.federation_sender":
-        if config.worker.send_federation:
-            sys.stderr.write(
-                "\nThe send_federation must be disabled in the main synapse process"
-                "\nbefore they can be run in a separate worker."
-                "\nPlease add ``send_federation: false`` to the main config"
-                "\n"
-            )
-            sys.exit(1)
-
-        # Force the pushers to start since they will be disabled in the main config
-        config.worker.send_federation = True
-    else:
-        # For other worker types we force this to off.
-        config.worker.send_federation = False
-
     synapse.events.USE_FROZEN_DICTS = config.use_frozen_dicts
 
     hs = GenericWorkerServer(