From d322f9312dda0603b0c3bddaa4e2e124990f524e Mon Sep 17 00:00:00 2001
From: Peter van Dijk <peter.van.dijk@powerdns.com>
Date: Wed, 24 Jul 2019 18:48:33 +0200
Subject: [PATCH] auth: add metric for open TCP connections

---
 docs/performance.rst                                | 6 ++++++
 pdns/common_startup.cc                              | 8 +++++++-
 pdns/tcpreceiver.cc                                 | 8 ++++++++
 pdns/tcpreceiver.hh                                 | 2 ++
 regression-tests.nobackend/counters/expected_result | 1 +
 5 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/docs/performance.rst b/docs/performance.rst
index e31ac892f7..850e352b9e 100644
--- a/docs/performance.rst
+++ b/docs/performance.rst
@@ -212,6 +212,12 @@ meta-cache-size
 ^^^^^^^^^^^^^^^
 Number of entries in the metadata cache
 
+.. _stat-open-tcp-connections:
+
+open-tcp-connections
+~~~~~~~~~~~~~~~~~~~~
+Number of currently open TCP connections
+
 .. _stat-overload-drops:
 
 overload-drops
diff --git a/pdns/common_startup.cc b/pdns/common_startup.cc
index 63a0d094f5..fa56dd6870 100644
--- a/pdns/common_startup.cc
+++ b/pdns/common_startup.cc
@@ -247,6 +247,11 @@ static uint64_t getSysUserTimeMsec(const std::string& str)
 
 }
 
+static uint64_t getTCPConnectionCount(const std::string& str)
+{
+  return TN->numTCPConnections();
+}
+
 static uint64_t getQCount(const std::string& str)
 try
 {
@@ -306,7 +311,8 @@ void declareStats(void)
   
   S.declare("tcp6-queries","Number of IPv6 TCP queries received");
   S.declare("tcp6-answers","Number of IPv6 answers sent out over TCP");
-    
+
+  S.declare("open-tcp-connections","Number of currently open TCP connections", getTCPConnectionCount);;
 
   S.declare("qsize-q","Number of questions waiting for database attention", getQCount);
 
diff --git a/pdns/tcpreceiver.cc b/pdns/tcpreceiver.cc
index 0ea41bb88f..c925766966 100644
--- a/pdns/tcpreceiver.cc
+++ b/pdns/tcpreceiver.cc
@@ -68,6 +68,7 @@ extern StatBag S;
 
 pthread_mutex_t TCPNameserver::s_plock = PTHREAD_MUTEX_INITIALIZER;
 Semaphore *TCPNameserver::d_connectionroom_sem;
+unsigned int TCPNameserver::d_maxTCPConnections = 0;
 PacketHandler *TCPNameserver::s_P; 
 NetmaskGroup TCPNameserver::d_ng;
 size_t TCPNameserver::d_maxTransactionsPerConn;
@@ -1195,6 +1196,7 @@ TCPNameserver::TCPNameserver()
 
 //  sem_init(&d_connectionroom_sem,0,::arg().asNum("max-tcp-connections"));
   d_connectionroom_sem = new Semaphore( ::arg().asNum( "max-tcp-connections" ));
+  d_maxTCPConnections = ::arg().asNum( "max-tcp-connections" );
   d_tid=0;
   vector<string>locals;
   stringtok(locals,::arg()["local-address"]," ,");
@@ -1387,3 +1389,9 @@ void TCPNameserver::thread()
 }
 
 
+unsigned int TCPNameserver::numTCPConnections()
+{
+  int room;
+  d_connectionroom_sem->getValue( &room);
+  return d_maxTCPConnections - room;
+}
diff --git a/pdns/tcpreceiver.hh b/pdns/tcpreceiver.hh
index cfd6d30016..fd8b33c22f 100644
--- a/pdns/tcpreceiver.hh
+++ b/pdns/tcpreceiver.hh
@@ -47,6 +47,7 @@ public:
   TCPNameserver();
   ~TCPNameserver();
   void go();
+  unsigned int numTCPConnections();
 private:
 
   static void sendPacket(std::shared_ptr<DNSPacket> p, int outsock);
@@ -65,6 +66,7 @@ private:
   static PacketHandler *s_P;
   pthread_t d_tid;
   static Semaphore *d_connectionroom_sem;
+  static unsigned int d_maxTCPConnections;
   static NetmaskGroup d_ng;
   static size_t d_maxTransactionsPerConn;
   static size_t d_maxConnectionsPerClient;
diff --git a/regression-tests.nobackend/counters/expected_result b/regression-tests.nobackend/counters/expected_result
index cf1ba2fd10..7e73f4fb65 100644
--- a/regression-tests.nobackend/counters/expected_result
+++ b/regression-tests.nobackend/counters/expected_result
@@ -11,6 +11,7 @@ dnsupdate-refused=0
 incoming-notifications=0
 key-cache-size=0
 meta-cache-size=3
+open-tcp-connections=0
 overload-drops=0
 packetcache-size=4
 qsize-q=0
-- 
2.39.2