From eadf0f4cc585b822ca72e05605b5237897353f43 Mon Sep 17 00:00:00 2001
From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Mon, 21 Mar 2022 10:27:30 +0100
Subject: [PATCH] dnsdist-1.7.x: Only allocate the health-check mplexer when
 needed

When health-checking is disabled, or when a check delay longer than one
second is used, there is no need to allocate a new multiplexer object
every second.

(cherry picked from commit 017337515725264173e4d1f254bc0a19e4da6f4a)
---
 pdns/dnsdist.cc | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/pdns/dnsdist.cc b/pdns/dnsdist.cc
index ea09c45487..057375cf55 100644
--- a/pdns/dnsdist.cc
+++ b/pdns/dnsdist.cc
@@ -1847,7 +1847,8 @@ static void healthChecksThread()
   for(;;) {
     sleep(interval);
 
-    auto mplexer = std::unique_ptr<FDMultiplexer>(FDMultiplexer::getMultiplexerSilent());
+    std::unique_ptr<FDMultiplexer> mplexer{nullptr};
+
     auto states = g_dstates.getLocal(); // this points to the actual shared_ptrs!
     for(auto& dss : *states) {
 
@@ -1900,14 +1901,19 @@ static void healthChecksThread()
       dss->lastCheck = 0;
 
       if (dss->availability == DownstreamState::Availability::Auto) {
+        if (!mplexer) {
+          mplexer = std::unique_ptr<FDMultiplexer>(FDMultiplexer::getMultiplexerSilent());
+        }
+
         if (!queueHealthCheck(mplexer, dss)) {
           updateHealthCheckResult(dss, false, false);
         }
       }
-
     }
 
-    handleQueuedHealthChecks(*mplexer);
+    if (mplexer) {
+      handleQueuedHealthChecks(*mplexer);
+    }
   }
 }
 
-- 
2.47.2