From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Tue, 13 Jan 2026 15:25:10 +0000 (+0100)
Subject: dnsdist: Do not keep stale cache entries around for empty pools
X-Git-Tag: rec-5.4.0-beta1~42^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F16721%2Fhead;p=thirdparty%2Fpdns.git

dnsdist: Do not keep stale cache entries around for empty pools

Signed-off-by: Remi Gacogne <remi.gacogne@powerdns.com>
---

diff --git a/pdns/dnsdistdist/dnsdist-backend.cc b/pdns/dnsdistdist/dnsdist-backend.cc
index 112655401c..a755f5be41 100644
--- a/pdns/dnsdistdist/dnsdist-backend.cc
+++ b/pdns/dnsdistdist/dnsdist-backend.cc
@@ -1152,6 +1152,11 @@ void ServerPool::setECS(bool useECS)
   updateConsistency();
 }
 
+bool ServerPool::shouldKeepStaleData() const
+{
+  return !getServers().empty() && countServers(true) == 0;
+}
+
 namespace dnsdist::backend
 {
 void registerNewBackend(std::shared_ptr<DownstreamState>& backend)
diff --git a/pdns/dnsdistdist/dnsdist-server-pool.hh b/pdns/dnsdistdist/dnsdist-server-pool.hh
index 78ba591aa9..9aa6d533fe 100644
--- a/pdns/dnsdistdist/dnsdist-server-pool.hh
+++ b/pdns/dnsdistdist/dnsdist-server-pool.hh
@@ -64,6 +64,7 @@ struct ServerPool
   size_t poolLoad() const;
   size_t countServers(bool upOnly) const;
   bool hasAtLeastOneServerAvailable() const;
+  bool shouldKeepStaleData() const;
   const ServerPolicy::NumberedServerVector& getServers() const;
   void addServer(std::shared_ptr<DownstreamState>& server);
   void removeServer(std::shared_ptr<DownstreamState>& server);
diff --git a/pdns/dnsdistdist/dnsdist.cc b/pdns/dnsdistdist/dnsdist.cc
index a4bebd84e4..200f4d3d4b 100644
--- a/pdns/dnsdistdist/dnsdist.cc
+++ b/pdns/dnsdistdist/dnsdist.cc
@@ -2426,7 +2426,7 @@ static void maintThread()
            has all its backends down) */
         if (packetCache->keepStaleData() && !iter->second) {
           /* so far all pools had at least one backend up */
-          if (pool.countServers(true) == 0) {
+          if (pool.shouldKeepStaleData()) {
             iter->second = true;
           }
         }
diff --git a/pdns/dnsdistdist/test-dnsdistserverpool.cc b/pdns/dnsdistdist/test-dnsdistserverpool.cc
index f9370adacf..d15a43aa77 100644
--- a/pdns/dnsdistdist/test-dnsdistserverpool.cc
+++ b/pdns/dnsdistdist/test-dnsdistserverpool.cc
@@ -59,6 +59,7 @@ BOOST_AUTO_TEST_CASE(test_ServerPoolBasics)
   BOOST_CHECK_EQUAL(pool.countServers(true), 0U);
   BOOST_CHECK_EQUAL(pool.countServers(false), 0U);
   BOOST_CHECK_EQUAL(pool.poolLoad(), 0U);
+  BOOST_CHECK(!pool.shouldKeepStaleData());
 
   {
     const auto& servers = pool.getServers();
@@ -76,6 +77,7 @@ BOOST_AUTO_TEST_CASE(test_ServerPoolBasics)
     BOOST_CHECK(!pool.hasAtLeastOneServerAvailable());
     BOOST_CHECK_EQUAL(pool.countServers(true), 0U);
     BOOST_CHECK_EQUAL(pool.countServers(false), 1U);
+    BOOST_CHECK(pool.shouldKeepStaleData());
 
     BOOST_CHECK_EQUAL(pool.poolLoad(), 0U);
     {
@@ -88,11 +90,13 @@ BOOST_AUTO_TEST_CASE(test_ServerPoolBasics)
     BOOST_CHECK(pool.hasAtLeastOneServerAvailable());
     BOOST_CHECK_EQUAL(pool.countServers(true), 1U);
     BOOST_CHECK_EQUAL(pool.countServers(false), 1U);
+    BOOST_CHECK(!pool.shouldKeepStaleData());
 
     /* now remove it */
     pool.removeServer(ds);
     BOOST_CHECK_EQUAL(pool.countServers(true), 0U);
     BOOST_CHECK_EQUAL(pool.countServers(false), 0U);
+    BOOST_CHECK(!pool.shouldKeepStaleData());
     {
       const auto& servers = pool.getServers();
       BOOST_CHECK(servers.empty());