From a8eab1f7e33e8d78c0a352938db3c68efac218c4 Mon Sep 17 00:00:00 2001
From: Evgeny Poberezkin <evgeny@poberezkin.com>
Date: Tue, 9 Sep 2025 22:53:42 +0100
Subject: [PATCH] concurrent read/write

---
 src/Simplex/Messaging/Server.hs  | 27 +++++++++++++++++++--------
 tests/CoreTests/MsgStoreTests.hs |  2 +-
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/Simplex/Messaging/Server.hs b/src/Simplex/Messaging/Server.hs
index 61748dd5b..02455846c 100644
--- a/src/Simplex/Messaging/Server.hs
+++ b/src/Simplex/Messaging/Server.hs
@@ -44,6 +44,7 @@ module Simplex.Messaging.Server
   )
 where
 
+import Control.Concurrent.Async (concurrently)
 import Control.Concurrent.STM (throwSTM)
 import Control.Logger.Simple
 import Control.Monad
@@ -74,7 +75,6 @@ import qualified Data.List.NonEmpty as L
 import Data.Map.Strict (Map)
 import qualified Data.Map.Strict as M
 import Data.Maybe (fromMaybe, isJust, isNothing)
-import Data.Semigroup (Sum (..))
 import qualified Data.Set as S
 import Data.Text (Text)
 import qualified Data.Text as T
@@ -2114,10 +2114,22 @@ exportMessages :: forall s. MsgStoreClass s => Bool -> MsgStore s -> FilePath ->
 exportMessages tty st f drainMsgs = do
   logNote $ "saving messages to file " <> T.pack f
   run $ case st of
-    StoreMemory ms -> exportMessages_ ms $ getMsgs ms
-    StoreJournal ms -> exportMessages_ ms $ getJournalMsgs ms
+    StoreMemory ms -> exportMessages_ getMsgs ms
+    StoreJournal ms -> exportMessages_ getJournalMsgs ms
   where
-    exportMessages_ ms get = fmap (\(Sum n) -> n) . unsafeWithAllMsgQueues tty ms . saveQueueMsgs get
+    exportMessages_ get ms h = do
+      saveQ <- newTBQueueIO 100
+      let readMsgs = do
+            unsafeWithAllMsgQueues tty ms $ \q ->
+              get ms q >>= \msgs -> unless (null msgs) $ atomically $ writeTBQueue saveQ $ Just (q, msgs)
+            atomically $ writeTBQueue saveQ Nothing
+          writeMsgs n =
+            atomically (readTBQueue saveQ) >>= \case
+              Nothing -> pure n
+              Just (q, msgs) -> do
+                n' <- saveQueueMsgs h q msgs
+                writeMsgs $ n + n'
+      snd <$> concurrently readMsgs (writeMsgs 0)
     run :: (Handle -> IO Int) -> IO ()
     run a = liftIO $ withFile f WriteMode $ tryAny . a >=> \case
       Right n -> logNote $ "messages saved: " <> tshow n
@@ -2130,11 +2142,10 @@ exportMessages tty st f drainMsgs = do
         Nothing -> getJournalQueueMessages ms q
     getMsgs :: MsgStoreClass s' => s' -> StoreQueue s' -> IO [Message]
     getMsgs ms q = unsafeRunStore q "saveQueueMsgs" $ getQueueMessages_ drainMsgs q =<< getMsgQueue ms q False
-    saveQueueMsgs :: (StoreQueue s -> IO [Message]) -> Handle -> StoreQueue s -> IO (Sum Int)
-    saveQueueMsgs get h q = do
-      msgs <- get q
+    saveQueueMsgs :: Handle -> StoreQueue s -> [Message] -> IO Int
+    saveQueueMsgs h q msgs = do
       unless (null msgs) $ BLD.hPutBuilder h $ encodeMessages (recipientId q) msgs
-      pure $ Sum $ length msgs
+      pure $ length msgs
     encodeMessages rId = mconcat . map (\msg -> BLD.byteString (strEncode $ MLRv3 rId msg) <> BLD.char8 '\n')
 
 processServerMessages :: forall s'. StartOptions -> M s' (Maybe MessageStats)
diff --git a/tests/CoreTests/MsgStoreTests.hs b/tests/CoreTests/MsgStoreTests.hs
index 2ed0da330..c5cf3a437 100644
--- a/tests/CoreTests/MsgStoreTests.hs
+++ b/tests/CoreTests/MsgStoreTests.hs
@@ -54,7 +54,7 @@ msgStoreTests = do
   around (withMsgStore testSMTStoreConfig) $ describe "STM message store" someMsgStoreTests
   around (withMsgStore $ testJournalStoreCfg MQStoreCfg) $ describe "Journal message store" $ do
     someMsgStoreTests
-    it "should export and import journal store" testExportImportStore
+    fit "should export and import journal store" testExportImportStore
     describe "queue state" $ do
       it "should restore queue state from the last line" testQueueState
       it "should recover when message is written and state is not" testMessageState