Clean up startup for the pusher (#6558)

* Remove redundant python2 support code

`str.decode()` doesn't exist on python3, so presumably this code was doing
nothing

* Filter out pushers with corrupt data

When we get a row with unparsable json, drop the row, rather than returning a
row with null `data`, which will then cause an explosion later on.

* Improve logging when we can't start a pusher

Log the ID to help us understand the problem

* Make email pusher setup more robust

We know we'll have a `data` member, since that comes from the database. What we
*don't* know is if that is a dict, and if that has a `brand` member, and if
that member is a string.

4 files changed, 37 insertions, 43 deletions

diff --git a/synapse/push/pusher.py b/synapse/push/pusher.py

index f277aeb131..8ad0bf5936 100644
--- a/synapse/push/pusher.py
+++ b/synapse/push/pusher.py
@@ -80,9 +80,11 @@ class PusherFactory(object):
         return EmailPusher(self.hs, pusherdict, mailer)
 
     def _app_name_from_pusherdict(self, pusherdict):
-        if "data" in pusherdict and "brand" in pusherdict["data"]:
-            app_name = pusherdict["data"]["brand"]
-        else:
-            app_name = self.config.email_app_name
+        data = pusherdict["data"]
 
-        return app_name
+        if isinstance(data, dict):
+            brand = data.get("brand")
+            if isinstance(brand, str):
+                return brand
+
+        return self.config.email_app_name
diff --git a/synapse/push/pusherpool.py b/synapse/push/pusherpool.py

index 0f6992202d..b9dca5bc63 100644
--- a/synapse/push/pusherpool.py
+++ b/synapse/push/pusherpool.py
@@ -232,7 +232,6 @@ class PusherPool:
             Deferred
         """
         pushers = yield self.store.get_all_pushers()
-        logger.info("Starting %d pushers", len(pushers))
 
         # Stagger starting up the pushers so we don't completely drown the
         # process on start up.
@@ -245,7 +244,7 @@ class PusherPool:
         """Start the given pusher
 
         Args:
-            pusherdict (dict):
+            pusherdict (dict): dict with the values pulled from the db table
 
         Returns:
             Deferred[EmailPusher|HttpPusher]
@@ -254,7 +253,8 @@ class PusherPool:
             p = self.pusher_factory.create_pusher(pusherdict)
         except PusherConfigException as e:
             logger.warning(
-                "Pusher incorrectly configured user=%s, appid=%s, pushkey=%s: %s",
+                "Pusher incorrectly configured id=%i, user=%s, appid=%s, pushkey=%s: %s",
+                pusherdict["id"],
                 pusherdict.get("user_name"),
                 pusherdict.get("app_id"),
                 pusherdict.get("pushkey"),
@@ -262,7 +262,9 @@ class PusherPool:
             )
             return
         except Exception:
-            logger.exception("Couldn't start a pusher: caught Exception")
+            logger.exception(
+                "Couldn't start pusher id %i: caught Exception", pusherdict["id"],
+            )
             return
 
         if not p:
diff --git a/synapse/rest/client/v1/pusher.py b/synapse/rest/client/v1/pusher.py

index 0791866f55..6f6b7aed6e 100644
--- a/synapse/rest/client/v1/pusher.py
+++ b/synapse/rest/client/v1/pusher.py
@@ -28,6 +28,17 @@ from synapse.rest.client.v2_alpha._base import client_patterns
 
 logger = logging.getLogger(__name__)
 
+ALLOWED_KEYS = {
+    "app_display_name",
+    "app_id",
+    "data",
+    "device_display_name",
+    "kind",
+    "lang",
+    "profile_tag",
+    "pushkey",
+}
+
 
 class PushersRestServlet(RestServlet):
     PATTERNS = client_patterns("/pushers$", v1=True)
@@ -43,23 +54,11 @@ class PushersRestServlet(RestServlet):
 
         pushers = await self.hs.get_datastore().get_pushers_by_user_id(user.to_string())
 
-        allowed_keys = [
-            "app_display_name",
-            "app_id",
-            "data",
-            "device_display_name",
-            "kind",
-            "lang",
-            "profile_tag",
-            "pushkey",
-        ]
-
-        for p in pushers:
-            for k, v in list(p.items()):
-                if k not in allowed_keys:
-                    del p[k]
-
-        return 200, {"pushers": pushers}
+        filtered_pushers = list(
+            {k: v for k, v in p.items() if k in ALLOWED_KEYS} for p in pushers
+        )
+
+        return 200, {"pushers": filtered_pushers}
 
     def on_OPTIONS(self, _):
         return 200, {}
diff --git a/synapse/storage/data_stores/main/pusher.py b/synapse/storage/data_stores/main/pusher.py

index f07309ef09..6b03233262 100644
--- a/synapse/storage/data_stores/main/pusher.py
+++ b/synapse/storage/data_stores/main/pusher.py
@@ -15,8 +15,7 @@
 # limitations under the License.
 
 import logging
-
-import six
+from typing import Iterable, Iterator
 
 from canonicaljson import encode_canonical_json, json
 
@@ -27,21 +26,16 @@ from synapse.util.caches.descriptors import cachedInlineCallbacks, cachedList
 
 logger = logging.getLogger(__name__)
 
-if six.PY2:
-    db_binary_type = six.moves.builtins.buffer
-else:
-    db_binary_type = memoryview
-
 
 class PusherWorkerStore(SQLBaseStore):
-    def _decode_pushers_rows(self, rows):
+    def _decode_pushers_rows(self, rows: Iterable[dict]) -> Iterator[dict]:
+        """JSON-decode the data in the rows returned from the `pushers` table
+
+        Drops any rows whose data cannot be decoded
+        """
         for r in rows:
             dataJson = r["data"]
-            r["data"] = None
             try:
-                if isinstance(dataJson, db_binary_type):
-                    dataJson = str(dataJson).decode("UTF8")
-
                 r["data"] = json.loads(dataJson)
             except Exception as e:
                 logger.warning(
@@ -50,12 +44,9 @@ class PusherWorkerStore(SQLBaseStore):
                     dataJson,
                     e.args[0],
                 )
-                pass
-
-            if isinstance(r["pushkey"], db_binary_type):
-                r["pushkey"] = str(r["pushkey"]).decode("UTF8")
+                continue
 
-        return rows
+            yield r
 
     @defer.inlineCallbacks
     def user_has_pusher(self, user_id):