Add multiplexed subscription testing

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6637
GitOrigin-RevId: a92b333b88c548ba514e69598a86098d8f6243cc

server/lib/api-tests/test/Test/Subscriptions/LiveQueriesSpec.hs

@@ -60,7 +60,7 @@ tests opts = withSubscriptions $ do
       shouldBe = shouldReturnYaml opts
 
   describe "Websockets-based live queries" do
-    it "Sanity check" \(mkSubscription, testEnvironment) -> do
+    it "Hasura sends updated query results after insert" \(mkSubscription, testEnvironment) -> do
       let schemaName :: Schema.SchemaName
           schemaName = Schema.getSchemaName testEnvironment
       query <-
@@ -122,7 +122,86 @@ tests opts = withSubscriptions $ do
                     - id: 2
                       name: "B"
               |]
+
+        getNextResponse query `shouldBe` expected
+
+    it "Multiplexes" \(mkSubscription, testEnvironment) -> do
+      let schemaName :: Schema.SchemaName
+          schemaName = Schema.getSchemaName testEnvironment
+
+      subIdEq3 <-
+        mkSubscription
+          [graphql|
+            subscription {
+              #{schemaName}_example(where: { id: { _eq: 3 } }) {
+                id
+                name
+              }
+            }
+          |]
+
+      subIdEq4 <-
+        mkSubscription
+          [graphql|
+            subscription {
+              #{schemaName}_example(where: { id: { _eq: 4 } }) {
+                id
+                name
+              }
+            }
+          |]
+
+      getNextResponse subIdEq3
+        `shouldBe` [yaml|
+        data:
+          hasura_example: []
+      |]
+
+      getNextResponse subIdEq4
+        `shouldBe` [yaml|
+        data:
+          hasura_example: []
+      |]
+
+      let expected :: Value
+          expected =
+            [yaml|
+              data:
+                insert_hasura_example:
+                  affected_rows: 2
+            |]
+
           actual :: IO Value
-            actual = getNextResponse query
+          actual =
+            postGraphql
+              testEnvironment
+              [graphql|
+                mutation {
+                  insert_#{schemaName}_example(
+                    objects:
+                      [ {id: 3, name: "A"},
+                        {id: 4, name: "B"}
+                      ]
+                  ) {
+                    affected_rows
+                  }
+                }
+              |]
 
       actual `shouldBe` expected
+
+      getNextResponse subIdEq3
+        `shouldBe` [yaml|
+        data:
+          hasura_example:
+            - id: 3
+              name: "A"
+      |]
+
+      getNextResponse subIdEq4
+        `shouldBe` [yaml|
+        data:
+          hasura_example:
+            - id: 4
+              name: "B"
+      |]

server/lib/test-harness/src/Harness/GraphqlEngine.hs

@@ -54,14 +54,16 @@ import Control.Lens (preview)
 import Control.Monad.Trans.Managed (ManagedT (..), lowerManagedT)
 import Data.Aeson
 import Data.Aeson.Encode.Pretty as AP
-import Data.Aeson.Lens (key)
+import Data.Aeson.Lens (key, _String)
 import Data.Aeson.QQ.Simple
 import Data.Aeson.Types (Pair)
 import Data.Environment qualified as Env
+import Data.IORef (IORef, atomicModifyIORef', newIORef, readIORef)
+import Data.Map.Strict qualified as Map
 import Data.Text qualified as T
 import Data.Time (getCurrentTime)
 import Harness.Constants qualified as Constants
-import Harness.Exceptions (SomeException (SomeException), bracket, catch, displayException, withFrozenCallStack)
+import Harness.Exceptions (bracket, throw, withFrozenCallStack)
 import Harness.Http qualified as Http
 import Harness.Quoter.Yaml (yaml)
 import Harness.TestEnvironment (BackendSettings (..), Server (..), TestEnvironment (..), getServer, serverUrl, testLog, testLogBytestring)
@@ -76,7 +78,6 @@ import Hasura.Server.Prometheus (makeDummyPrometheusMetrics)
 import Network.Socket qualified as Socket
 import Network.Wai.Handler.Warp qualified as Warp
 import Network.WebSockets qualified as WS
-import System.Log.FastLogger
 import System.Metrics qualified as EKG
 import System.Timeout (timeout)
 import Test.Hspec
@@ -417,13 +418,26 @@ withSubscriptions = aroundAllWith \actionWithSubAndTest testEnvironment -> do
     -- send initialization message
     WS.sendTextData conn (encode initMessage)
 
-    -- open communication channel with responses
-    messageMVar <- newEmptyMVar
+    -- Open communication channel with responses.
+    --
+    -- TODO: this currently doesn't capture any notion of ordering across
+    -- subscriptions (only within a single subscription). This might be
+    -- something we want to change in future. For now, we can tell that
+    -- response @S@ comes before response @T@ with a single identifier.
+    handlers <- newIORef Map.empty
 
     -- counter for subscriptions
     subNextId <- newTVarIO 1
 
-    let -- Is this an actual message or client/server busywork?
+    let -- Shorthand for an 'atomicModifyIORef'' call that returns no information.
+        atomicModify :: IORef x -> (x -> x) -> IO ()
+        atomicModify ref f = atomicModifyIORef' ref \x -> (f x, ())
+
+        -- Convenience function for converting JSON values to strings.
+        jsonToString :: Value -> String
+        jsonToString = T.unpack . WS.fromLazyByteString . encode
+
+        -- Is this an actual message or client/server busywork?
         isInteresting :: Value -> Bool
         isInteresting res =
           preview (key "type") res
@@ -431,62 +445,71 @@ withSubscriptions = aroundAllWith \actionWithSubAndTest testEnvironment -> do
                         Just "connection_ack" -- connection acknowledged
                       ]
 
-        -- listens for server responses and populates @messageMVar@ with the new response.
-        -- It will only read one message at a time because it is blocked by reading/writing
-        -- to the MVar.
-        -- Will throw an exception to the other thread if it encounters an error.
+        -- listens for server responses and populates @handlers@ with the new
+        -- response. It will only read one message at a time because it is
+        -- blocked by reading/writing to the MVar. Will throw an exception to
+        -- the other thread if it encounters an error.
         responseListener :: IO ()
         responseListener = do
           res <- eitherDecode <$> WS.receiveData conn
+
           case res of
             Left err -> do
-              logger testEnvironment $ toLogStr $ "subscription decode failed: " ++ err
-              putMVar messageMVar (Left err)
+              testLog testEnvironment $ "subscription decode failed: " ++ err
+              throw $ userError err
             Right msg -> do
               when (isInteresting msg) do
-                logger testEnvironment (toLogStr $ "subscriptions message: " ++ show msg)
-                case preview (key "payload") msg of
+                testLog testEnvironment $ "subscriptions message: " ++ jsonToString msg
+
+                let maybePayload :: Maybe Value
+                    maybePayload = preview (key "payload") msg
+
+                    maybeIdentifier :: Maybe Text
+                    maybeIdentifier = preview (key "id" . _String) msg
+
+                case liftA2 (,) maybePayload maybeIdentifier of
                   Nothing -> do
-                    logger testEnvironment (toLogStr ("Unable to parse message" :: Text))
-                    putMVar messageMVar (Left $ "Unable to parse message: " ++ show msg)
-                  Just payload -> putMVar messageMVar (Right payload)
+                    testLog testEnvironment "Unable to parse message"
+                    throw $ userError ("Unable to parse message: " ++ show msg)
+                  Just (payload, identifier) ->
+                    readIORef handlers >>= \mvars ->
+                      case Map.lookup identifier mvars of
+                        Just mvar -> putMVar mvar (Right payload)
+                        Nothing -> throw (userError "Unexpected handler identifier")
+
               responseListener
 
-        -- Create a subscription over this websocket connection.
-        -- Will be used by the user to create new subscriptions.
-        -- The handled can be used to request the next response.
+        -- Create a subscription over this websocket connection. Will be used
+        -- by the user to create new subscriptions. The handled can be used to
+        -- request the next response.
         mkSub :: Value -> IO SubscriptionHandle
         mkSub query = do
           -- each subscription has an id, this manages a new id for each subscription.
           subId <- atomically do
             currSubId <- readTVar subNextId
             let !next = currSubId + 1
+
             writeTVar subNextId next
             pure currSubId
+
+          messageBox <- newEmptyMVar
+          atomicModify handlers (Map.insert (tshow subId) messageBox)
+
           -- initialize a connection.
           WS.sendTextData conn (encode $ startQueryMessage subId query)
-          pure $ SubscriptionHandle messageMVar
+          pure $ SubscriptionHandle messageBox
 
         handleExceptionsAndTimeout action = do
           let time = seconds subscriptionsTimeoutTime
-          catch
-            ( do
-                res <-
-                  timeout
-                    (fromIntegral $ diffTimeToMicroSeconds time)
-                    action
-                case res of
-                  Nothing ->
-                    error ("Subscription exceeded the allotted time of: " <> show time)
-                  Just () ->
-                    pure ()
-            )
-            ( \(SomeException err) ->
-                putMVar messageMVar (Left $ displayException err)
-            )
 
-    _ <- Async.async (handleExceptionsAndTimeout responseListener)
+          timeout (fromIntegral $ diffTimeToMicroSeconds time) action >>= \case
+            Nothing -> throw $ userError do
+              "Subscription exceeded the allotted time of: " <> show time
+            Just _ -> pure ()
 
+    -- @withAsync@ will take care of cancelling the 'responseListener' thread
+    -- for us once the test has been executed.
+    Async.withAsync (handleExceptionsAndTimeout responseListener) \_ -> do
       actionWithSubAndTest (mkSub, testEnvironment)
 
 -- | Get the next response received on a subscription.