diff --git a/changelog.d/4567.misc b/changelog.d/4567.misc
new file mode 100644
index 000000000..96a2e0aef
--- /dev/null
+++ b/changelog.d/4567.misc
@@ -0,0 +1 @@
+Reduce duplication of ``synapse.app`` code.
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index 5b97a54d4..3cbb00303 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -15,7 +15,9 @@
 
 import gc
 import logging
+import signal
 import sys
+import traceback
 
 import psutil
 from daemonize import Daemonize
@@ -23,11 +25,25 @@ from daemonize import Daemonize
 from twisted.internet import error, reactor
 
 from synapse.app import check_bind_error
+from synapse.crypto import context_factory
 from synapse.util import PreserveLoggingContext
 from synapse.util.rlimit import change_resource_limit
 
 logger = logging.getLogger(__name__)
 
+_sighup_callbacks = []
+
+
+def register_sighup(func):
+    """
+    Register a function to be called when a SIGHUP occurs.
+
+    Args:
+        func (function): Function to be called when sent a SIGHUP signal.
+            Will be called with a single argument, the homeserver.
+    """
+    _sighup_callbacks.append(func)
+
 
 def start_worker_reactor(appname, config):
     """ Run the reactor in the main process
@@ -189,3 +205,50 @@ def listen_ssl(
 
     logger.info("Synapse now listening on port %d (TLS)", port)
     return r
+
+
+def refresh_certificate(hs):
+    """
+    Refresh the TLS certificates that Synapse is using by re-reading them from
+    disk and updating the TLS context factories to use them.
+    """
+    logging.info("Loading certificate from disk...")
+    hs.config.read_certificate_from_disk()
+    hs.tls_server_context_factory = context_factory.ServerContextFactory(hs.config)
+    hs.tls_client_options_factory = context_factory.ClientTLSOptionsFactory(
+        hs.config
+    )
+    logging.info("Certificate loaded.")
+
+
+def start(hs, listeners=None):
+    """
+    Start a Synapse server or worker.
+
+    Args:
+        hs (synapse.server.HomeServer)
+        listeners (list[dict]): Listener configuration ('listeners' in homeserver.yaml)
+    """
+    try:
+        # Set up the SIGHUP machinery.
+        if hasattr(signal, "SIGHUP"):
+            def handle_sighup(*args, **kwargs):
+                for i in _sighup_callbacks:
+                    i(hs)
+
+            signal.signal(signal.SIGHUP, handle_sighup)
+
+            register_sighup(refresh_certificate)
+
+        # Load the certificate from disk.
+        refresh_certificate(hs)
+
+        # It is now safe to start your Synapse.
+        hs.start_listening(listeners)
+        hs.get_datastore().start_profiling()
+    except Exception:
+        traceback.print_exc(file=sys.stderr)
+        reactor = hs.get_reactor()
+        if reactor.running:
+            reactor.stop()
+        sys.exit(1)
diff --git a/synapse/app/appservice.py b/synapse/app/appservice.py
index 8559e141a..33107f56d 100644
--- a/synapse/app/appservice.py
+++ b/synapse/app/appservice.py
@@ -168,12 +168,7 @@ def start(config_options):
     )
 
     ps.setup()
-    ps.start_listening(config.worker_listeners)
-
-    def start():
-        ps.get_datastore().start_profiling()
-
-    reactor.callWhenRunning(start)
+    reactor.callWhenRunning(_base.start, ps, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-appservice", config)
 
diff --git a/synapse/app/client_reader.py b/synapse/app/client_reader.py
index f8a417cb6..a9d214702 100644
--- a/synapse/app/client_reader.py
+++ b/synapse/app/client_reader.py
@@ -25,7 +25,6 @@ from synapse.app import _base
 from synapse.config._base import ConfigError
 from synapse.config.homeserver import HomeServerConfig
 from synapse.config.logger import setup_logging
-from synapse.crypto import context_factory
 from synapse.http.server import JsonResource
 from synapse.http.site import SynapseSite
 from synapse.metrics import RegistryProxy
@@ -173,17 +172,7 @@ def start(config_options):
     )
 
     ss.setup()
-
-    def start():
-        ss.config.read_certificate_from_disk()
-        ss.tls_server_context_factory = context_factory.ServerContextFactory(config)
-        ss.tls_client_options_factory = context_factory.ClientTLSOptionsFactory(
-            config
-        )
-        ss.start_listening(config.worker_listeners)
-        ss.get_datastore().start_profiling()
-
-    reactor.callWhenRunning(start)
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-client-reader", config)
 
diff --git a/synapse/app/event_creator.py b/synapse/app/event_creator.py
index 656e0edc0..b8e519615 100644
--- a/synapse/app/event_creator.py
+++ b/synapse/app/event_creator.py
@@ -25,7 +25,6 @@ from synapse.app import _base
 from synapse.config._base import ConfigError
 from synapse.config.homeserver import HomeServerConfig
 from synapse.config.logger import setup_logging
-from synapse.crypto import context_factory
 from synapse.http.server import JsonResource
 from synapse.http.site import SynapseSite
 from synapse.metrics import RegistryProxy
@@ -194,17 +193,7 @@ def start(config_options):
     )
 
     ss.setup()
-
-    def start():
-        ss.config.read_certificate_from_disk()
-        ss.tls_server_context_factory = context_factory.ServerContextFactory(config)
-        ss.tls_client_options_factory = context_factory.ClientTLSOptionsFactory(
-            config
-        )
-        ss.start_listening(config.worker_listeners)
-        ss.get_datastore().start_profiling()
-
-    reactor.callWhenRunning(start)
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-event-creator", config)
 
diff --git a/synapse/app/federation_reader.py b/synapse/app/federation_reader.py
index 3de271513..42886dbfc 100644
--- a/synapse/app/federation_reader.py
+++ b/synapse/app/federation_reader.py
@@ -26,7 +26,6 @@ from synapse.app import _base
 from synapse.config._base import ConfigError
 from synapse.config.homeserver import HomeServerConfig
 from synapse.config.logger import setup_logging
-from synapse.crypto import context_factory
 from synapse.federation.transport.server import TransportLayerServer
 from synapse.http.site import SynapseSite
 from synapse.metrics import RegistryProxy
@@ -160,17 +159,7 @@ def start(config_options):
     )
 
     ss.setup()
-
-    def start():
-        ss.config.read_certificate_from_disk()
-        ss.tls_server_context_factory = context_factory.ServerContextFactory(config)
-        ss.tls_client_options_factory = context_factory.ClientTLSOptionsFactory(
-            config
-        )
-        ss.start_listening(config.worker_listeners)
-        ss.get_datastore().start_profiling()
-
-    reactor.callWhenRunning(start)
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-federation-reader", config)
 
diff --git a/synapse/app/federation_sender.py b/synapse/app/federation_sender.py
index d944e0517..a461442fd 100644
--- a/synapse/app/federation_sender.py
+++ b/synapse/app/federation_sender.py
@@ -25,7 +25,6 @@ from synapse.app import _base
 from synapse.config._base import ConfigError
 from synapse.config.homeserver import HomeServerConfig
 from synapse.config.logger import setup_logging
-from synapse.crypto import context_factory
 from synapse.federation import send_queue
 from synapse.http.site import SynapseSite
 from synapse.metrics import RegistryProxy
@@ -192,17 +191,8 @@ def start(config_options):
     )
 
     ss.setup()
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
-    def start():
-        ss.config.read_certificate_from_disk()
-        ss.tls_server_context_factory = context_factory.ServerContextFactory(config)
-        ss.tls_client_options_factory = context_factory.ClientTLSOptionsFactory(
-            config
-        )
-        ss.start_listening(config.worker_listeners)
-        ss.get_datastore().start_profiling()
-
-    reactor.callWhenRunning(start)
     _base.start_worker_reactor("synapse-federation-sender", config)
 
 
diff --git a/synapse/app/frontend_proxy.py b/synapse/app/frontend_proxy.py
index d9ef6edc3..d5b954361 100644
--- a/synapse/app/frontend_proxy.py
+++ b/synapse/app/frontend_proxy.py
@@ -26,7 +26,6 @@ from synapse.app import _base
 from synapse.config._base import ConfigError
 from synapse.config.homeserver import HomeServerConfig
 from synapse.config.logger import setup_logging
-from synapse.crypto import context_factory
 from synapse.http.server import JsonResource
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
 from synapse.http.site import SynapseSite
@@ -250,17 +249,7 @@ def start(config_options):
     )
 
     ss.setup()
-
-    def start():
-        ss.config.read_certificate_from_disk()
-        ss.tls_server_context_factory = context_factory.ServerContextFactory(config)
-        ss.tls_client_options_factory = context_factory.ClientTLSOptionsFactory(
-            config
-        )
-        ss.start_listening(config.worker_listeners)
-        ss.get_datastore().start_profiling()
-
-    reactor.callWhenRunning(start)
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-frontend-proxy", config)
 
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index 250a17cef..1a341568a 100755
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -17,7 +17,6 @@
 import gc
 import logging
 import os
-import signal
 import sys
 import traceback
 
@@ -28,7 +27,6 @@ from prometheus_client import Gauge
 
 from twisted.application import service
 from twisted.internet import defer, reactor
-from twisted.protocols.tls import TLSMemoryBIOFactory
 from twisted.web.resource import EncodingResourceWrapper, NoResource
 from twisted.web.server import GzipEncoderFactory
 from twisted.web.static import File
@@ -49,7 +47,6 @@ from synapse.app import _base
 from synapse.app._base import listen_ssl, listen_tcp, quit_with_error
 from synapse.config._base import ConfigError
 from synapse.config.homeserver import HomeServerConfig
-from synapse.crypto import context_factory
 from synapse.federation.transport.server import TransportLayerServer
 from synapse.http.additional_resource import AdditionalResource
 from synapse.http.server import RootRedirect
@@ -241,10 +238,10 @@ class SynapseHomeServer(HomeServer):
 
         return resources
 
-    def start_listening(self):
+    def start_listening(self, listeners):
         config = self.get_config()
 
-        for listener in config.listeners:
+        for listener in listeners:
             if listener["type"] == "http":
                 self._listening_services.extend(
                     self._listener_http(config, listener)
@@ -328,20 +325,11 @@ def setup(config_options):
         # generating config files and shouldn't try to continue.
         sys.exit(0)
 
-    sighup_callbacks = []
     synapse.config.logger.setup_logging(
         config,
-        use_worker_options=False,
-        register_sighup=sighup_callbacks.append
+        use_worker_options=False
     )
 
-    def handle_sighup(*args, **kwargs):
-        for i in sighup_callbacks:
-            i(*args, **kwargs)
-
-    if hasattr(signal, "SIGHUP"):
-        signal.signal(signal.SIGHUP, handle_sighup)
-
     events.USE_FROZEN_DICTS = config.use_frozen_dicts
 
     database_engine = create_engine(config.database_config)
@@ -377,31 +365,6 @@ def setup(config_options):
 
     hs.setup()
 
-    def refresh_certificate(*args):
-        """
-        Refresh the TLS certificates that Synapse is using by re-reading them
-        from disk and updating the TLS context factories to use them.
-        """
-        logging.info("Reloading certificate from disk...")
-        hs.config.read_certificate_from_disk()
-        hs.tls_server_context_factory = context_factory.ServerContextFactory(config)
-        hs.tls_client_options_factory = context_factory.ClientTLSOptionsFactory(
-            config
-        )
-        logging.info("Certificate reloaded.")
-
-        logging.info("Updating context factories...")
-        for i in hs._listening_services:
-            if isinstance(i.factory, TLSMemoryBIOFactory):
-                i.factory = TLSMemoryBIOFactory(
-                    hs.tls_server_context_factory,
-                    False,
-                    i.factory.wrappedFactory
-                )
-        logging.info("Context factories updated.")
-
-    sighup_callbacks.append(refresh_certificate)
-
     @defer.inlineCallbacks
     def start():
         try:
@@ -425,18 +388,9 @@ def setup(config_options):
                 ):
                     yield acme.provision_certificate()
 
-            # Read the certificate from disk and build the context factories for
-            # TLS.
-            hs.config.read_certificate_from_disk()
-            hs.tls_server_context_factory = context_factory.ServerContextFactory(config)
-            hs.tls_client_options_factory = context_factory.ClientTLSOptionsFactory(
-                config
-            )
+            _base.start(hs, config.listeners)
 
-            # It is now safe to start your Synapse.
-            hs.start_listening()
             hs.get_pusherpool().start()
-            hs.get_datastore().start_profiling()
             hs.get_datastore().start_doing_background_updates()
         except Exception as e:
             # If a DeferredList failed (like in listening on the ACME listener),
diff --git a/synapse/app/media_repository.py b/synapse/app/media_repository.py
index 4ecf64031..d4cc4e944 100644
--- a/synapse/app/media_repository.py
+++ b/synapse/app/media_repository.py
@@ -26,7 +26,6 @@ from synapse.app import _base
 from synapse.config._base import ConfigError
 from synapse.config.homeserver import HomeServerConfig
 from synapse.config.logger import setup_logging
-from synapse.crypto import context_factory
 from synapse.http.site import SynapseSite
 from synapse.metrics import RegistryProxy
 from synapse.metrics.resource import METRICS_PREFIX, MetricsResource
@@ -160,17 +159,7 @@ def start(config_options):
     )
 
     ss.setup()
-
-    def start():
-        ss.config.read_certificate_from_disk()
-        ss.tls_server_context_factory = context_factory.ServerContextFactory(config)
-        ss.tls_client_options_factory = context_factory.ClientTLSOptionsFactory(
-            config
-        )
-        ss.start_listening(config.worker_listeners)
-        ss.get_datastore().start_profiling()
-
-    reactor.callWhenRunning(start)
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-media-repository", config)
 
diff --git a/synapse/app/pusher.py b/synapse/app/pusher.py
index 83b0863f0..cbf0d67f5 100644
--- a/synapse/app/pusher.py
+++ b/synapse/app/pusher.py
@@ -224,11 +224,10 @@ def start(config_options):
     )
 
     ps.setup()
-    ps.start_listening(config.worker_listeners)
 
     def start():
+        _base.start(ps, config.worker_listeners)
         ps.get_pusherpool().start()
-        ps.get_datastore().start_profiling()
 
     reactor.callWhenRunning(start)
 
diff --git a/synapse/app/synchrotron.py b/synapse/app/synchrotron.py
index 0354e82bf..9163b56d8 100644
--- a/synapse/app/synchrotron.py
+++ b/synapse/app/synchrotron.py
@@ -445,12 +445,7 @@ def start(config_options):
     )
 
     ss.setup()
-    ss.start_listening(config.worker_listeners)
-
-    def start():
-        ss.get_datastore().start_profiling()
-
-    reactor.callWhenRunning(start)
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-synchrotron", config)
 
diff --git a/synapse/app/user_dir.py b/synapse/app/user_dir.py
index 176d55a78..d1ab9512c 100644
--- a/synapse/app/user_dir.py
+++ b/synapse/app/user_dir.py
@@ -26,7 +26,6 @@ from synapse.app import _base
 from synapse.config._base import ConfigError
 from synapse.config.homeserver import HomeServerConfig
 from synapse.config.logger import setup_logging
-from synapse.crypto import context_factory
 from synapse.http.server import JsonResource
 from synapse.http.site import SynapseSite
 from synapse.metrics import RegistryProxy
@@ -220,17 +219,7 @@ def start(config_options):
     )
 
     ss.setup()
-
-    def start():
-        ss.config.read_certificate_from_disk()
-        ss.tls_server_context_factory = context_factory.ServerContextFactory(config)
-        ss.tls_client_options_factory = context_factory.ClientTLSOptionsFactory(
-            config
-        )
-        ss.start_listening(config.worker_listeners)
-        ss.get_datastore().start_profiling()
-
-    reactor.callWhenRunning(start)
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-user-dir", config)
 
diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index a795e39b1..4b938053f 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -15,7 +15,6 @@
 import logging
 import logging.config
 import os
-import signal
 import sys
 from string import Template
 
@@ -24,6 +23,7 @@ import yaml
 from twisted.logger import STDLibLogObserver, globalLogBeginner
 
 import synapse
+from synapse.app import _base as appbase
 from synapse.util.logcontext import LoggingContextFilter
 from synapse.util.versionstring import get_version_string
 
@@ -127,7 +127,7 @@ class LoggingConfig(Config):
                 )
 
 
-def setup_logging(config, use_worker_options=False, register_sighup=None):
+def setup_logging(config, use_worker_options=False):
     """ Set up python logging
 
     Args:
@@ -140,12 +140,6 @@ def setup_logging(config, use_worker_options=False, register_sighup=None):
         register_sighup (func | None): Function to call to register a
             sighup handler.
     """
-    if not register_sighup:
-        if getattr(signal, "SIGHUP"):
-            register_sighup = lambda x: signal.signal(signal.SIGHUP, x)
-        else:
-            register_sighup = lambda x: None
-
     log_config = (config.worker_log_config if use_worker_options
                   else config.log_config)
     log_file = (config.worker_log_file if use_worker_options
@@ -187,7 +181,7 @@ def setup_logging(config, use_worker_options=False, register_sighup=None):
         else:
             handler = logging.StreamHandler()
 
-            def sighup(signum, stack):
+            def sighup(*args):
                 pass
 
         handler.setFormatter(formatter)
@@ -200,14 +194,14 @@ def setup_logging(config, use_worker_options=False, register_sighup=None):
             with open(log_config, 'r') as f:
                 logging.config.dictConfig(yaml.load(f))
 
-        def sighup(signum, stack):
+        def sighup(*args):
             # it might be better to use a file watcher or something for this.
             load_log_config()
             logging.info("Reloaded log config from %s due to SIGHUP", log_config)
 
         load_log_config()
 
-    register_sighup(sighup)
+    appbase.register_sighup(sighup)
 
     # make sure that the first thing we log is a thing we can grep backwards
     # for