Ensure many batches are able to be imported (MSC2716)

tests/msc2716_test.go

@@ -207,6 +207,54 @@ func TestImportHistoricalMessages(t *testing.T) {
 			}
 		})
 
+		t.Run("Many batches are able to be imported and recalled from /messages", func(t *testing.T) {
+			t.Parallel()
+
+			roomID := as.CreateRoom(t, createPublicRoomOpts)
+			alice.JoinRoom(t, roomID, nil)
+
+			// Create some normal messages in the timeline
+			eventIDsBefore := createMessagesInRoom(t, alice, roomID, 2)
+			eventIdBefore := eventIDsBefore[len(eventIDsBefore)-1]
+			timeAfterEventBefore := time.Now()
+
+			// wait X number of ms to ensure that the timestamp changes enough for
+			// each of the historical messages we try to import later
+			numBatches := 11
+			numHistoricalMessagesPerBatch := 100
+			time.Sleep(time.Duration(numBatches*numHistoricalMessagesPerBatch) * timeBetweenMessages)
+
+			// eventIDsAfter
+			createMessagesInRoom(t, alice, roomID, 2)
+
+			// Import a long chain of batches connected to each other.
+			// We want to make sure Synapse doesn't blow up after we import
+			// many messages.
+			nextBatchID := ""
+			for i := 0; i < numBatches; i++ {
+				insertTime := timeAfterEventBefore.Add(timeBetweenMessages * time.Duration(numBatches-numHistoricalMessagesPerBatch*i))
+				batchSendRes := batchSendHistoricalMessages(
+					t,
+					as,
+					roomID,
+					eventIdBefore,
+					nextBatchID,
+					createJoinStateEventsForBatchSendRequest([]string{virtualUserID}, insertTime),
+					createMessageEventsForBatchSendRequest([]string{virtualUserID}, insertTime, numHistoricalMessagesPerBatch),
+					// Status
+					200,
+				)
+				batchSendResBody := client.ParseJSON(t, batchSendRes)
+				nextBatchID = client.GetJSONFieldStr(t, batchSendResBody, "next_batch_id")
+			}
+
+			// Ensure the /message response gives a 200
+			alice.MustDoFunc(t, "GET", []string{"_matrix", "client", "r0", "rooms", roomID, "messages"}, client.WithContentType("application/json"), client.WithQueries(url.Values{
+				"dir":   []string{"b"},
+				"limit": []string{"100"},
+			}))
+		})
+
 		t.Run("Historical events from multiple users in the same batch", func(t *testing.T) {
 			t.Parallel()