From 8f4d603dcdb8ea52eaf604d456c79a8ba5973408 Mon Sep 17 00:00:00 2001
From: Philipp Kant <philipp@infinipool.com>
Date: Fri, 17 Jul 2015 14:57:11 +0200
Subject: [PATCH] Close thunk leak in roundstats.

The function performFetches collects statistics about the requests
performed in each round. However, the list is not evaluated (unless
tracing is on), leading to an accumulation of thunks. Forcing the list
via deepseq prevents this.
---
 Haxl/Core/Monad.hs | 3 ++-
 haxl.cabal         | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/Haxl/Core/Monad.hs b/Haxl/Core/Monad.hs
index 5745e85..8ea50c4 100644
--- a/Haxl/Core/Monad.hs
+++ b/Haxl/Core/Monad.hs
@@ -56,6 +56,7 @@ import Control.Exception (AllocationLimitExceeded(..))
 import Control.Monad
 import qualified Control.Exception as Exception
 import Control.Applicative hiding (Const)
+import Control.DeepSeq
 import GHC.Exts (IsString(..))
 #if __GLASGOW_HASKELL__ < 706
 import Prelude hiding (catch)
@@ -526,7 +527,7 @@ performFetches n env reqs = do
   let roundtime = realToFrac (diffUTCTime t1 t0) :: Double
 
   ifReport f 1 $
-    modifyIORef' sref $ \(Stats rounds) ->
+    modifyIORef' sref $ \(Stats rounds) -> roundstats `deepseq`
       Stats (RoundStats (microsecs roundtime) dsroundstats: rounds)
 
   ifTrace f 1 $
diff --git a/haxl.cabal b/haxl.cabal
index 73db83c..89983cc 100644
--- a/haxl.cabal
+++ b/haxl.cabal
@@ -31,6 +31,7 @@ library
     base == 4.*,
     bytestring >= 0.9 && < 0.11,
     containers == 0.5.*,
+    deepseq,
     directory >= 1.1 && < 1.3,
     filepath >= 1.3 && < 1.5,
     hashable == 1.2.*,