spent an injustifiable amount of time making graphs..

diff --git a/pdns/README-dnsdist.md b/pdns/README-dnsdist.md
index c866fcc3901f09e0a43f0fdc74dfd2b2f81dca70..6708d6c339b3b61522a6f2c0c3f328bf94333c0c 100644 (file)
--- a/pdns/README-dnsdist.md
+++ b/pdns/README-dnsdist.md
@@ -155,6 +155,32 @@ This is still much in flux, but for now, try:
  * `topResponses(20, 2)`: top-20 servfail responses (use ,3 for NXDOMAIN)
 
 
+Live histogram of latency
+-------------------------
+```
+> showResponseLatency()
+Average response latency: 78.84 msec, median: 87.59 msec
+   msec        
+   0.10        
+   0.20        .
+   0.40        **********************
+   0.80        ***********
+   1.60        .
+   3.20        
+   6.40        .
+  12.80        *
+  25.60        *
+  51.20        *
+ 102.40        **********************************************************************
+ 204.80        *************************
+ 409.60        **
+ 819.20        :
+1638.40        .
+```
+
+Where : stands for 'half a star' and . for 'less than half a star, but
+something was there'.
+
 Per domain or subnet QPS limiting
 ---------------------------------
 If certain domains or source addresses are generating onerous amounts of

diff --git a/pdns/dnsdist.cc b/pdns/dnsdist.cc
index 117001f516c0085f20683c9d01e5386d68006b69..67af8a60bd84e0abf7d3115147846f57755882ea 100644 (file)
--- a/pdns/dnsdist.cc
+++ b/pdns/dnsdist.cc
@@ -19,6 +19,11 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
+#include <boost/accumulators/statistics/median.hpp>
+#include <boost/accumulators/statistics/mean.hpp>
+#include <boost/accumulators/accumulators.hpp>
+#include <boost/accumulators/statistics.hpp>
+
 #include "ext/luawrapper/include/LuaContext.hpp"
 #include <boost/circular_buffer.hpp>
 #include "sstuff.hh"
@@ -27,7 +32,8 @@
 #include "statbag.hh"
 #include <netinet/tcp.h>
 #include <boost/program_options.hpp>
-#include <boost/foreach.hpp>
+
+
 #include <thread>
 #include <limits>
 #include <atomic>
@@ -1284,6 +1290,60 @@ void setupLua(bool client)
   g_lua.executeCode(R"(function topResponses(top, kind, labels) for k,v in ipairs(getTopResponses(top, kind, labels)) do show(string.format("%4d  %-40s %4d %4.1f%%",k,v[1],v[2], v[3])) end end)");
 
 
+  g_lua.writeFunction("showResponseLatency", []() {
+
+      map<double, unsigned int> histo;
+      double bin=100;
+      for(int i=0; i < 15; ++i) {
+       histo[bin];
+       bin*=2;
+      }
+
+      using namespace boost::accumulators;
+
+      typedef boost::accumulators::accumulator_set<
+       unsigned int
+       , stats<boost::accumulators::tag::median(with_p_square_quantile),
+               boost::accumulators::tag::mean(immediate)
+               >
+       > acc_t;
+      acc_t lats;
+
+      {
+       std::lock_guard<std::mutex> lock(g_rings.respMutex);
+       
+       for(const auto& r : g_rings.respRing) {
+         auto iter = histo.lower_bound(r.usec);
+         if(iter != histo.end())
+           iter->second++;
+         else
+           histo.rbegin()++;
+         lats(r.usec);
+       }
+      }
+
+      g_outputBuffer = (boost::format("Average response latency: %.02f msec, median: %.02f msec\n") % (0.001*mean(lats)) % (0.001*median(lats))).str();
+      double highest=0;
+      
+      for(auto iter = histo.cbegin(); iter != histo.cend(); ++iter) {
+       highest=std::max(highest, iter->second*1.0);
+      }
+      boost::format fmt("%7.2f\t%s\n");
+      g_outputBuffer += (fmt % "msec" % "").str();
+
+      for(auto iter = histo.cbegin(); iter != histo.cend(); ++iter) {
+       int stars = (70.0 * iter->second/highest);
+       char c='*';
+       if(!stars && iter->second) {
+         stars=1; // you get 1 . to show something is there..
+         if(70.0*iter->second/highest > 0.5)
+           c=':';
+         else
+           c='.';
+       }
+       g_outputBuffer += (fmt % (iter->first/1000.0) % string(stars, c)).str();
+      }
+    });
 
   g_lua.writeFunction("newQPSLimiter", [](int rate, int burst) { return QPSLimiter(rate, burst); });
   g_lua.registerFunction("check", &QPSLimiter::check);