From 43e46dd8ccbd7c72d87b02e93d7c64886033b355 Mon Sep 17 00:00:00 2001
From: sh <37271604+shumvgolove@users.noreply.github.com>
Date: Fri, 10 Jul 2026 12:00:40 +0400
Subject: [PATCH] smp-server: fix service subscription memory leak (#1827)

Service subscription counters (totalServiceSubs, serviceSubsCount,
ntfServiceSubsCount) are TVar (Int64, IdsHash). modifyTVar' only forces
the pair to WHNF, so `n +/- n'` and `idsHash <> idsHash'` stay
unevaluated and accumulate an unbounded thunk chain under subscription
and delivery churn (the IdsHash chain also retains a bytestring per
update) - a space leak proportional to the number of updates.

Force both components in addServiceSubs/subtractServiceSubs. Verified
with the load bench: svc churn drops from +5.4 KiB/iter (linear) to flat.
---
 src/Simplex/Messaging/Protocol.hs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Simplex/Messaging/Protocol.hs b/src/Simplex/Messaging/Protocol.hs
index 8ef5bb04f..8730597f3 100644
--- a/src/Simplex/Messaging/Protocol.hs
+++ b/src/Simplex/Messaging/Protocol.hs
@@ -1546,11 +1546,14 @@ queueIdHash = IdsHash . C.md5Hash . unEntityId
 {-# INLINE queueIdHash #-}
 
 addServiceSubs :: (Int64, IdsHash) -> (Int64, IdsHash) -> (Int64, IdsHash)
-addServiceSubs (n', idsHash') (n, idsHash) = (n + n', idsHash <> idsHash')
+addServiceSubs (n', idsHash') (n, idsHash) =
+  let !n'' = n + n'
+      !h = idsHash <> idsHash'
+   in (n'', h)
 
 subtractServiceSubs :: (Int64, IdsHash) -> (Int64, IdsHash) -> (Int64, IdsHash)
 subtractServiceSubs (n', idsHash') (n, idsHash)
-  | n > n' = (n - n', idsHash <> idsHash') -- concat is a reversible xor: (x `xor` y) `xor` y == x
+  | n > n' = let !n'' = n - n'; !h = idsHash <> idsHash' in (n'', h) -- concat is a reversible xor: (x `xor` y) `xor` y == x
   | otherwise = (0, mempty)
 
 data ProtocolErrorType = PECmdSyntax | PECmdUnknown | PESession | PEBlock