Specify a limit on the number of EDUs and PDUs a transaction can contain

api/server-server/definitions/transaction.yaml

@@ -31,7 +31,7 @@ properties:
     example: 1532991320875
   pdus:
     type: array
-    description: List of persistent updates to rooms.
+    description: List of persistent updates to rooms. Must not include more than 50 PDUs.
     items:
       $ref: "pdu.yaml"
 required: ['origin', 'origin_server_ts', 'pdus']

api/server-server/transactions.yaml

@@ -60,8 +60,8 @@ paths:
                   edus:
                     type: array
                     description: |-
-                      List of ephemeral messages. May be omitted if there are no ephemeral 
-                      messages to be sent.
+                      List of ephemeral messages. May be omitted if there are no ephemeral
+                      messages to be sent. Must not include more than 100 EDUs.
                     items:
                       $ref: "definitions/edu.yaml"
           example: {

specification/server_server_api.rst

@@ -262,6 +262,8 @@ of Transaction messages, which are encoded as JSON objects, passed over an HTTP
 PUT request. A Transaction is meaningful only to the pair of homeservers that
 exchanged it; they are not globally-meaningful.
 
+Transactions are limited in size; they can have at most 50 PDUs and 100 EDUs.
+
 {{transactions_ss_http_api}}
 
 PDUs