Server-side call cancellation (#26)

* begin module with LowLevel tests of Op stuff, cancel functions, refactor Ops a little.

* refactor op tests, add server-side cancellation test

* add cancel function for unregistered calls, move some unregistered stuff

* remove unnecessary threadDelay

* update test description

* fix init metadata api for registered server calls

* pass call into handler for cancelling, add cancel test

examples/echo/echo-server/Main.hs

@@ -8,13 +8,14 @@ import           Control.Monad                             (forever)
 import           Data.ByteString                           (ByteString)
 import           Network.GRPC.LowLevel
 import qualified Network.GRPC.LowLevel.Server.Unregistered as U
+import qualified Network.GRPC.LowLevel.Call.Unregistered as U
 
 serverMeta :: MetadataMap
 serverMeta = [("test_meta", "test_meta_value")]
 
-handler :: ByteString -> MetadataMap -> MethodName
+handler :: U.ServerCall -> ByteString -> MetadataMap -> MethodName
            -> IO (ByteString, MetadataMap, StatusDetails)
-handler reqBody _reqMeta _method = do
+handler _call reqBody _reqMeta _method = do
   --putStrLn $ "Got request for method: " ++ show method
   --putStrLn $ "Got metadata: " ++ show reqMeta
   return (reqBody, serverMeta, StatusDetails "")
@@ -34,7 +35,7 @@ regMain = withGRPC $ \grpc -> do
     forever $ do
       let method = head (registeredMethods server)
       result <- serverHandleNormalCall server method 15 serverMeta $
-        \reqBody _reqMeta -> return (reqBody, serverMeta, serverMeta,
+        \_call reqBody _reqMeta -> return (reqBody, serverMeta,
                                            StatusDetails "")
       case result of
         Left x -> putStrLn $ "registered call result error: " ++ show x
@@ -44,7 +45,7 @@ regMain = withGRPC $ \grpc -> do
 regLoop :: Server -> RegisteredMethod -> IO ()
 regLoop server method = forever $ do
   result <- serverHandleNormalCall server method 15 serverMeta $
-    \reqBody _reqMeta -> return (reqBody, serverMeta, serverMeta,
+    \_call reqBody _reqMeta -> return (reqBody, serverMeta,
                                        StatusDetails "")
   case result of
     Left x -> putStrLn $ "registered call result error: " ++ show x

grpc-haskell.cabal

@@ -44,7 +44,6 @@ library
     Network.GRPC.LowLevel
     Network.GRPC.LowLevel.Server.Unregistered
     Network.GRPC.LowLevel.Client.Unregistered
-  other-modules:
     Network.GRPC.LowLevel.CompletionQueue
     Network.GRPC.LowLevel.CompletionQueue.Internal
     Network.GRPC.LowLevel.CompletionQueue.Unregistered
@@ -117,6 +116,7 @@ test-suite test
     , containers ==0.5.*
   other-modules:
     LowLevelTests,
+    LowLevelTests.Op,
     UnsafeTests
   default-language:     Haskell2010
   ghc-options:          -Wall -fwarn-incomplete-patterns -fno-warn-unused-do-bind -g -threaded

src/Network/GRPC/LowLevel.hs

@@ -34,6 +34,7 @@ GRPC
 , withServer
 , serverHandleNormalCall
 , withServerCall
+, serverCallCancel
 
 -- * Client
 , ClientConfig(..)
@@ -45,6 +46,7 @@ GRPC
 , clientRegisterMethod
 , clientRequest
 , withClientCall
+, clientCallCancel
 
 -- * Ops
 , Op(..)

src/Network/GRPC/LowLevel/Call.hs

@@ -17,6 +17,7 @@ import qualified Network.GRPC.Unsafe            as C
 import qualified Network.GRPC.Unsafe.ByteBuffer as C
 import qualified Network.GRPC.Unsafe.Metadata   as C
 import qualified Network.GRPC.Unsafe.Time       as C
+import qualified Network.GRPC.Unsafe.Op         as C
 
 import           Network.GRPC.LowLevel.GRPC     (MetadataMap, grpcDebug)
 
@@ -56,6 +57,9 @@ data RegisteredMethod = RegisteredMethod {methodType :: GRPCMethodType,
 -- This is used to associate send/receive 'Op's with a request.
 data ClientCall = ClientCall { unClientCall :: C.Call }
 
+clientCallCancel :: ClientCall -> IO ()
+clientCallCancel cc = C.grpcCallCancel (unClientCall cc) C.reserved
+
 -- | Represents one registered GRPC call on the server. Contains pointers to all
 -- the C state needed to respond to a registered call.
 data ServerCall = ServerCall
@@ -66,6 +70,10 @@ data ServerCall = ServerCall
     callDeadline        :: C.CTimeSpecPtr
   }
 
+serverCallCancel :: ServerCall -> C.StatusCode -> String -> IO ()
+serverCallCancel sc code reason =
+  C.grpcCallCancelWithStatus (unServerCall sc) code reason C.reserved
+
 serverCallGetMetadata :: ServerCall -> IO MetadataMap
 serverCallGetMetadata ServerCall{..} = do
   marray <- peek requestMetadataRecv

src/Network/GRPC/LowLevel/Call/Unregistered.hs

@@ -10,6 +10,7 @@ import           Network.GRPC.LowLevel.Call   (Host (..), MethodName (..))
 import           Network.GRPC.LowLevel.GRPC   (MetadataMap, grpcDebug)
 import qualified Network.GRPC.Unsafe          as C
 import qualified Network.GRPC.Unsafe.Metadata as C
+import qualified Network.GRPC.Unsafe.Op as C
 
 -- | Represents one unregistered GRPC call on the server.
 -- Contains pointers to all the C state needed to respond to an unregistered
@@ -21,6 +22,10 @@ data ServerCall = ServerCall
   , callDetails         :: C.CallDetails
   }
 
+serverCallCancel :: ServerCall -> C.StatusCode -> String -> IO ()
+serverCallCancel sc code reason =
+  C.grpcCallCancelWithStatus (unServerCall sc) code reason C.reserved
+
 serverCallGetMetadata :: ServerCall -> IO MetadataMap
 serverCallGetMetadata ServerCall{..} = do
   marray <- peek requestMetadataRecv

src/Network/GRPC/LowLevel/CompletionQueue.hs

@@ -128,10 +128,9 @@ serverRequestCall :: C.Server
                   -> CompletionQueue
                   -> TimeoutSeconds
                   -> RegisteredMethod
-                  -> MetadataMap
                   -> IO (Either GRPCIOError ServerCall)
 serverRequestCall
-  server cq@CompletionQueue{..} timeLimit RegisteredMethod{..} initMeta =
+  server cq@CompletionQueue{..} timeLimit RegisteredMethod{..} =
     withPermission Push cq $ do
       -- TODO: Is gRPC supposed to populate this deadline?
       -- NOTE: the below stuff is freed when we free the call we return.
@@ -139,15 +138,6 @@ serverRequestCall
       callPtr <- malloc
       metadataArrayPtr <- C.metadataArrayCreate
       metadataArray <- peek metadataArrayPtr
-      #ifdef DEBUG
-      metaCount <- C.metadataArrayGetCount metadataArray
-      metaCap <- C.metadataArrayGetCapacity metadataArray
-      kvPtr <- C.metadataArrayGetMetadata metadataArray
-      grpcDebug $ "grpc-created meta: count: " ++ show metaCount
-                  ++ " capacity: " ++ show metaCap ++ " ptr: " ++ show kvPtr
-      #endif
-      metadataContents <- C.createMetadata initMeta
-      C.metadataArraySetMetadata metadataArray metadataContents
       bbPtr <- malloc
       tag <- newTag cq
       callError <- C.grpcServerRequestRegisteredCall

src/Network/GRPC/LowLevel/Op.hs

@@ -129,15 +129,17 @@ freeOpContext (OpRecvCloseOnServerContext pcancelled) =
   grpcDebug ("freeOpContext: freeing pcancelled: " ++ show pcancelled)
   >> free pcancelled
 
--- | Converts a list of 'Op's into the corresponding 'OpContext's and guarantees
--- they will be cleaned up correctly.
-withOpContexts :: [Op] -> ([OpContext] -> IO a) -> IO a
-withOpContexts ops = bracket (mapM createOpContext ops)
-                             (mapM freeOpContext)
-
-withOpArray :: Int -> (C.OpArray -> IO a) -> IO a
-withOpArray n = bracket (C.opArrayCreate n)
-                        (flip C.opArrayDestroy n)
+-- | Allocates an `OpArray` and a list of `OpContext`s from the given list of
+-- `Op`s. 
+withOpArrayAndCtxts :: [Op] -> ((C.OpArray, [OpContext]) -> IO a) -> IO a
+withOpArrayAndCtxts ops = bracket setup teardown
+  where setup = do ctxts <- mapM createOpContext ops
+                   let l = length ops
+                   arr <- C.opArrayCreate l
+                   sequence_ $ zipWith (setOpArray arr) [0..l-1] ctxts
+                   return (arr, ctxts)
+        teardown (arr, ctxts) = do C.opArrayDestroy arr (length ctxts)
+                                   mapM_ freeOpContext ctxts
 
 -- | Container holding GC-managed results for 'Op's which receive data.
 data OpRecvResult =
@@ -216,11 +218,8 @@ runOps :: C.Call
        -> IO (Either GRPCIOError [OpRecvResult])
 runOps call cq ops timeLimit =
   let l = length ops in
-    withOpArray l $ \opArray -> do
-      grpcDebug "runOps: created op array."
-      withOpContexts ops $ \contexts -> do
+    withOpArrayAndCtxts ops $ \(opArray, contexts) -> do
       grpcDebug $ "runOps: allocated op contexts: " ++ show contexts
-        sequence_ $ zipWith (setOpArray opArray) [0..l-1] contexts
       tag <- newTag cq
       callError <- startBatch cq call opArray l tag
       grpcDebug $ "runOps: called start_batch. callError: "

src/Network/GRPC/LowLevel/Server.hs

@@ -125,42 +125,23 @@ serverRegisterMethod _ _ _ _ = error "Streaming methods not implemented yet."
 serverCreateCall :: Server
                  -> RegisteredMethod
                  -> TimeoutSeconds
-                 -> MetadataMap
                  -> IO (Either GRPCIOError ServerCall)
-serverCreateCall Server{..} rm timeLimit initMeta =
-  serverRequestCall internalServer serverCQ timeLimit rm initMeta
+serverCreateCall Server{..} rm timeLimit =
+  serverRequestCall internalServer serverCQ timeLimit rm
 
 withServerCall :: Server
                -> RegisteredMethod
                -> TimeoutSeconds
-               -> MetadataMap
                -> (ServerCall -> IO (Either GRPCIOError a))
                -> IO (Either GRPCIOError a)
-withServerCall server regmethod timeout initMeta f = do
-  createResult <- serverCreateCall server regmethod timeout initMeta
+withServerCall server regmethod timeout f = do
+  createResult <- serverCreateCall server regmethod timeout
   case createResult of
     Left x -> return $ Left x
     Right call -> f call `finally` logDestroy call
       where logDestroy c = grpcDebug "withServerRegisteredCall: destroying."
                            >> destroyServerCall c
 
--- | Sequence of 'Op's needed to receive a normal (non-streaming) call.
-serverOpsGetNormalCall :: MetadataMap -> [Op]
-serverOpsGetNormalCall initMetadata =
-  [OpSendInitialMetadata initMetadata,
-   OpRecvMessage]
-
--- | Sequence of 'Op's needed to respond to a normal (non-streaming) call.
-serverOpsSendNormalResponse :: ByteString
-                               -> MetadataMap
-                               -> C.StatusCode
-                               -> StatusDetails
-                               -> [Op]
-serverOpsSendNormalResponse body metadata code details =
-  [OpRecvCloseOnServer,
-   OpSendMessage body,
-   OpSendStatusFromServer metadata code details]
-
 serverOpsSendNormalRegisteredResponse :: ByteString
                                          -> MetadataMap
                                          -- ^ initial metadata
@@ -180,13 +161,14 @@ serverOpsSendNormalRegisteredResponse
 -- body, with the bytestring response body in the result tuple. The first
 -- metadata parameter refers to the request metadata, with the two metadata
 -- values in the result tuple being the initial and trailing metadata
--- respectively.
+-- respectively. We pass in the 'ServerCall' so that the server can call
+-- 'serverCallCancel' on it if needed.
 
 -- TODO: make a more rigid type for this with a Maybe MetadataMap for the
 -- trailing meta, and use it for both kinds of call handlers.
 type ServerHandler
-  =  ByteString -> MetadataMap
-  -> IO (ByteString, MetadataMap, MetadataMap, StatusDetails)
+  =  ServerCall -> ByteString -> MetadataMap
+  -> IO (ByteString, MetadataMap, StatusDetails)
 
 -- TODO: we will want to replace this with some more general concept that also
 -- works with streaming calls in the future.
@@ -198,12 +180,12 @@ serverHandleNormalCall :: Server
                        -- ^ Initial server metadata
                        -> ServerHandler
                        -> IO (Either GRPCIOError ())
-serverHandleNormalCall s@Server{..} rm timeLimit srvMetadata f = do
+serverHandleNormalCall s@Server{..} rm timeLimit initMeta f = do
   -- TODO: we use this timeLimit twice, so the max time spent is 2*timeLimit.
   -- Should we just hard-code time limits instead? Not sure if client
   -- programmer cares, since this function will likely just be put in a loop
   -- anyway.
-  withServerCall s rm timeLimit srvMetadata $ \call -> do
+  withServerCall s rm timeLimit $ \call -> do
     grpcDebug "serverHandleNormalCall(R): starting batch."
     debugServerCall call
     payload <- serverCallGetPayload call
@@ -213,7 +195,7 @@ serverHandleNormalCall s@Server{..} rm timeLimit srvMetadata f = do
       Nothing -> error "serverHandleNormalCall(R): payload empty."
       Just requestBody -> do
         requestMeta <- serverCallGetMetadata call
-        (respBody, initMeta, trailingMeta, details) <- f requestBody requestMeta
+        (respBody, trailingMeta, details) <- f call requestBody requestMeta
         let status = C.GrpcStatusOk
         let respOps = serverOpsSendNormalRegisteredResponse
                         respBody initMeta trailingMeta status details

src/Network/GRPC/LowLevel/Server/Unregistered.hs

@@ -9,10 +9,8 @@ import           Network.GRPC.LowLevel.Call.Unregistered
 import           Network.GRPC.LowLevel.CompletionQueue              (TimeoutSeconds)
 import           Network.GRPC.LowLevel.CompletionQueue.Unregistered (serverRequestCall)
 import           Network.GRPC.LowLevel.GRPC
-import           Network.GRPC.LowLevel.Op                           (OpRecvResult (..), runOps)
-import           Network.GRPC.LowLevel.Server                       (Server (..),
-                                                                     serverOpsGetNormalCall,
-                                                                     serverOpsSendNormalResponse)
+import           Network.GRPC.LowLevel.Op                           (Op(..), OpRecvResult (..), runOps)
+import           Network.GRPC.LowLevel.Server                       (Server (..))
 import qualified Network.GRPC.Unsafe.Op                             as C
 
 serverCreateCall :: Server -> TimeoutSeconds
@@ -31,10 +29,30 @@ withServerCall server timeout f = do
       where logDestroy c = grpcDebug "withServerCall: destroying."
                            >> destroyServerCall c
 
+-- | Sequence of 'Op's needed to receive a normal (non-streaming) call.
+-- TODO: We have to put 'OpRecvCloseOnServer' in the response ops, or else the
+-- client times out. Given this, I have no idea how to check for cancellation on
+-- the server.
+serverOpsGetNormalCall :: MetadataMap -> [Op]
+serverOpsGetNormalCall initMetadata =
+  [OpSendInitialMetadata initMetadata,
+   OpRecvMessage]
+
+-- | Sequence of 'Op's needed to respond to a normal (non-streaming) call.
+serverOpsSendNormalResponse :: ByteString
+                               -> MetadataMap
+                               -> C.StatusCode
+                               -> StatusDetails
+                               -> [Op]
+serverOpsSendNormalResponse body metadata code details =
+  [OpRecvCloseOnServer,
+   OpSendMessage body,
+   OpSendStatusFromServer metadata code details]
+
 -- | A handler for an unregistered server call; bytestring arguments are the
 -- request body and response body respectively.
 type ServerHandler
-  =  ByteString -> MetadataMap -> MethodName
+  =  ServerCall -> ByteString -> MetadataMap -> MethodName
   -> IO (ByteString, MetadataMap, StatusDetails)
 
 -- | Handle one unregistered call.
@@ -58,7 +76,7 @@ serverHandleNormalCall s@Server{..} timeLimit srvMetadata f = do
         methodName <- serverCallGetMethodName call
         hostName <- serverCallGetHost call
         grpcDebug $ "call_details host is: " ++ show hostName
-        (respBody, respMetadata, details) <- f body requestMeta methodName
+        (respBody, respMetadata, details) <- f call body requestMeta methodName
         let status = C.GrpcStatusOk
         let respOps = serverOpsSendNormalResponse
                         respBody respMetadata status details

tests/LowLevelTests.hs

@@ -3,7 +3,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RecordWildCards   #-}
 
-module LowLevelTests (lowLevelTests) where
+module LowLevelTests where
 
 import           Control.Concurrent                        (threadDelay)
 import           Control.Concurrent.Async
@@ -34,6 +34,7 @@ lowLevelTests = testGroup "Unit tests of low-level Haskell library"
   -- , testWrongEndpoint
   , testPayload
   , testPayloadUnregistered
+  , testServerCancel
   , testGoaway
   , testSlowServer
   ]
@@ -78,8 +79,8 @@ testServerTimeoutNoClient :: TestTree
 testServerTimeoutNoClient =
   serverOnlyTest "wait timeout when client DNE" [("/foo", Normal)] $ \s -> do
     let rm = head (registeredMethods s)
-    r <- serverHandleNormalCall s rm 1 mempty $ \_ _ ->
-           return ("", mempty, mempty, StatusDetails "details")
+    r <- serverHandleNormalCall s rm 1 mempty $ \_ _ _ ->
+           return ("", mempty, StatusDetails "details")
     r @?= Left GRPCIOTimeout
 
 -- TODO: fix this test: currently, client seems to hang and server times out,
@@ -99,8 +100,8 @@ testWrongEndpoint =
     server s = do
       length (registeredMethods s) @?= 1
       let rm = head (registeredMethods s)
-      r <- serverHandleNormalCall s rm 10 mempty $ \_ _ -> do
-        return ("reply test", dummyMeta, dummyMeta, StatusDetails "details string")
+      r <- serverHandleNormalCall s rm 10 mempty $ \_ _ _ -> do
+        return ("reply test", dummyMeta, StatusDetails "details string")
       r @?= Right ()
 
 -- TODO: There seems to be a race here (and in other client/server pairs, of
@@ -126,10 +127,27 @@ testPayload =
     server s = do
       length (registeredMethods s) @?= 1
       let rm = head (registeredMethods s)
-      r <- serverHandleNormalCall s rm 11 mempty $ \reqBody reqMD -> do
+      r <- serverHandleNormalCall s rm 11 dummyMeta $ \_ reqBody reqMD -> do
         reqBody @?= "Hello!"
         checkMD "Server metadata mismatch" clientMD reqMD
-        return ("reply test", dummyMeta, dummyMeta, StatusDetails "details string")
+        return ("reply test", dummyMeta, StatusDetails "details string")
+      r @?= Right ()
+
+testServerCancel :: TestTree
+testServerCancel =
+  csTest "server cancel call" client server [("/foo", Normal)]
+  where
+    client c = do
+      rm <- clientRegisterMethod c "/foo" Normal
+      res <- clientRequest c rm 10 "" mempty
+      res @?= Left (GRPCIOBadStatusCode GrpcStatusCancelled
+                                        (StatusDetails
+                                          "Received RST_STREAM err=8"))
+    server s = do
+      let rm = head (registeredMethods s)
+      r <- serverHandleNormalCall s rm 10 mempty $ \c _ _ -> do
+        serverCallCancel c GrpcStatusCancelled ""
+        return (mempty, mempty, "")
       r @?= Right ()
 
 testPayloadUnregistered :: TestTree
@@ -143,7 +161,7 @@ testPayloadUnregistered =
           rspBody @?= "reply test"
           details @?= "details string"
     server s = do
-      r <- U.serverHandleNormalCall s 11 mempty $ \body _md meth -> do
+      r <- U.serverHandleNormalCall s 11 mempty $ \_ body _md meth -> do
              body @?= "Hello!"
              meth @?= "/foo"
              return ("reply test", mempty, "details string")
@@ -184,9 +202,9 @@ testSlowServer =
         result == deadlineExceededStatus
     server s = do
       let rm = head (registeredMethods s)
-      serverHandleNormalCall s rm 1 mempty $ \_ _ -> do
+      serverHandleNormalCall s rm 1 mempty $ \_ _ _ -> do
         threadDelay (2*10^(6 :: Int))
-        return ("", mempty, mempty, StatusDetails "")
+        return ("", mempty, StatusDetails "")
       return ()
 
 --------------------------------------------------------------------------------
@@ -195,9 +213,9 @@ testSlowServer =
 dummyMeta :: M.Map ByteString ByteString
 dummyMeta = [("foo","bar")]
 
-dummyHandler :: ByteString -> MetadataMap
-                -> IO (ByteString, MetadataMap, MetadataMap, StatusDetails)
-dummyHandler _ _ = return ("", mempty, mempty, StatusDetails "")
+dummyHandler :: ServerCall -> ByteString -> MetadataMap
+                -> IO (ByteString, MetadataMap, StatusDetails)
+dummyHandler _ _ _ = return ("", mempty, StatusDetails "")
 
 unavailableStatus :: Either GRPCIOError a
 unavailableStatus =

tests/LowLevelTests/Op.hs

@@ -0,0 +1,104 @@
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE RecordWildCards #-}
+
+module LowLevelTests.Op where
+
+import           Control.Concurrent             (threadDelay)
+import           Control.Concurrent.Async
+import           Control.Monad
+import           Data.ByteString                (ByteString, isPrefixOf)
+import qualified Data.Map                       as M
+import           Foreign.Storable               (peek)
+import           Test.Tasty
+import           Test.Tasty.HUnit               as HU (testCase, (@?=),
+                                                       assertBool)
+
+import           Network.GRPC.LowLevel
+import           Network.GRPC.LowLevel.Call
+import           Network.GRPC.LowLevel.Client
+import           Network.GRPC.LowLevel.Server
+import           Network.GRPC.LowLevel.Op
+import           Network.GRPC.LowLevel.CompletionQueue
+
+lowLevelOpTests :: TestTree
+lowLevelOpTests = testGroup "Synchronous unit tests of low-level Op interface"
+  [testCancelWhileHandling
+  ,testCancelFromServer]
+
+testCancelWhileHandling :: TestTree
+testCancelWhileHandling =
+  testCase "Client/Server - cancel after handler starts does nothing" $
+  runSerialTest $ \grpc ->
+    withClientServerUnaryCall grpc $
+    \(c@Client{..}, s@Server{..}, cc@ClientCall{..}, sc@ServerCall{..}) -> do
+      withOpArrayAndCtxts serverEmptyRecvOps $ \(opArray, ctxts) -> do
+        tag <- newTag serverCQ
+        startBatch serverCQ unServerCall opArray 3 tag
+        pluck serverCQ tag 1
+        let (OpRecvCloseOnServerContext pcancelled) = last ctxts
+        cancelledBefore <- peek pcancelled
+        cancelledBefore @?= 0
+        clientCallCancel cc
+        threadDelay 1000000
+        cancelledAfter <- peek pcancelled
+        cancelledAfter @?= 0
+        return $ Right ()
+
+testCancelFromServer :: TestTree
+testCancelFromServer =
+  testCase "Client/Server - client receives server cancellation" $
+  runSerialTest $ \grpc ->
+    withClientServerUnaryCall grpc $
+    \(c@Client{..}, s@Server{..}, cc@ClientCall{..}, sc@ServerCall{..}) -> do
+      serverCallCancel sc GrpcStatusPermissionDenied "TestStatus"
+      clientRes <- runOps unClientCall clientCQ clientRecvOps 1
+      case clientRes of
+        Left x -> error $ "Client recv error: " ++ show x
+        Right [_,_,OpRecvStatusOnClientResult _ code details] -> do
+          code @?= GrpcStatusPermissionDenied
+          assertBool "Received status details or RST_STREAM error" $
+            details == "TestStatus"
+            ||
+            isPrefixOf "Received RST_STREAM" details
+          return $ Right ()
+
+
+runSerialTest :: (GRPC -> IO (Either GRPCIOError ())) -> IO ()
+runSerialTest f =
+  withGRPC f >>= \case Left x -> error $ show x
+                       Right () -> return ()
+
+withClientServerUnaryCall :: GRPC
+                             -> ((Client, Server, ClientCall, ServerCall)
+                                 -> IO (Either GRPCIOError a))
+                             -> IO (Either GRPCIOError a)
+withClientServerUnaryCall grpc f = do
+  withClient grpc clientConf $ \c -> do
+    crm <- clientRegisterMethod c "/foo" Normal
+    withServer grpc serverConf $ \s ->
+      withClientCall c crm 10 $ \cc -> do
+        let srm = head (registeredMethods s)
+        -- NOTE: We need to send client ops here or else `withServerCall` hangs,
+        -- because registered methods try to do recv ops immediately when
+        -- created. If later we want to send payloads or metadata, we'll need
+        -- to tweak this.
+        clientRes <- runOps (unClientCall cc) (clientCQ c) clientEmptySendOps 1
+        withServerCall s srm 10 $ \sc ->
+          f (c, s, cc, sc)
+
+serverConf = (ServerConfig "localhost" 50051 [("/foo", Normal)])
+
+clientConf = (ClientConfig "localhost" 50051)
+
+clientEmptySendOps = [OpSendInitialMetadata mempty,
+                      OpSendMessage "",
+                      OpSendCloseFromClient]
+
+clientRecvOps = [OpRecvInitialMetadata,
+                 OpRecvMessage,
+                 OpRecvStatusOnClient]
+
+serverEmptyRecvOps = [OpSendInitialMetadata mempty,
+                      OpRecvMessage,
+                      OpRecvCloseOnServer]

tests/Properties.hs

@@ -1,9 +1,11 @@
 import           LowLevelTests
+import           LowLevelTests.Op
 import           Test.Tasty
 import           UnsafeTests
 
 main :: IO ()
 main = defaultMain $ testGroup "GRPC Unit Tests"
   [ unsafeTests
+  , lowLevelOpTests
   , lowLevelTests
   ]