[Pdns-users] Pdns Remote vs Pipe backend performance

[Aleksey Chudov]

Hello,

I have a custom written Java application which I would like to use as a 
PowerDNS backend. After examining documentation I have come to the 
conclusion that Pipe and Remote backends suitable for my needs.

Because of the java application architecture is difficult to use it 
through the pipe. So, to compare the performance of different backends, 
I asked our programmers to implement in our java application support for 
Pipe protocol over unix socket and Remote protocol over unix socket and 
Remote over http.

Unfortunately In the current implementation PowerDNS Pipe can not pass 
parameters to the application. So I had to change coprocess.cc code to 
connect from PowerDNS Pipe and Remote Pipe to the unix socket using 
socat binary.

--- pdns-3.2.orig/modules/pipebackend/coprocess.cc    2013-01-17 
13:16:53.000000000 +0400
+++ pdns-3.2/modules/pipebackend/coprocess.cc    2013-03-02 
15:12:04.415022452 +0400
@@ -9,12 +9,20 @@
  #include <sys/wait.h>
  #include <pdns/misc.hh>
  #include <pdns/ahuexception.hh>
+#include <boost/algorithm/string.hpp>
+#include <vector>

  CoProcess::CoProcess(const string &command,int timeout, int infd, int 
outfd)
  {
-  const char *argv[2];
-  argv[0]=strdup(command.c_str());
-  argv[1]=0;
+  vector <string> v;
+
+  split(v, command, is_any_of(" "));
+
+  const char *argv[v.size()+1];
+
+  for (size_t n = 0; n < v.size(); n++)
+    argv[n]=strdup(v[n].c_str());
+  argv[v.size()]=0;

    launch(argv,timeout,infd,outfd);
  }


After making these changes it is possible to set one of the following 
parameter in the configuration file to test different backends

# For remote backend
remote-connection-string=http:url=http://127.0.0.1:8090/dnsapi
remote-connection-string=unix:path=/var/run/pdns/remote.sock
remote-connection-string=pipe:command=/usr/bin/socat stdio 
unix-connect:/var/run/pdns/remote.sock

# For pipe backend
pipe-command=/usr/bin/socat stdio unix-connect:/var/run/pdns/pipe.sock


All tests were conducted on a dedicated physical server with the 
following configuration
ETegro Hyperion RS130 G3 / 2x Intel E5620 @ 2.40GHz / 16GB RAM / 
PowerDNS + Pipe or Remote backend

PowerDNS running with the following configuration
cache-ttl=0
distributor-threads=1/7 (maximum performance achieved with 
distributor-threads = 7)
launch=remote/pipe
query-cache-ttl=0

16 dedicated physical servers are used as DNS clients. Each server 
running two instances of dnsperf with the following parameters
dnsperf -d dnsperf1.txt -s 1.1.1.1
dnsperf -d dnsperf2.txt -s 1.1.1.1

Content of dnsperf1.txt
test1.example.com. A

Content of dnsperf2.txt
test2.example.com. A

Results
|PowerDNS Backend|Threads|Transaction rate|
|PowerDNS 3.2 + Remote HTTP|1|1700|
|PowerDNS 3.2 + Remote HTTP|7|8973|
|PowerDNS 3.2 + Remote Socket|1|7043|
|PowerDNS 3.2 + Remote Socket|7|28205|
|PowerDNS 3.2 + Remote Pipe + Socat|1|4215|
|PowerDNS 3.2 + Remote Pipe + Socat|7|15898|
|PowerDNS 3.2 + Pipe + Socat|1|4786|
|PowerDNS 3.2 + Pipe + Socat|7|25926|

As seen the fastest backend is Remote over unix socket.

If compare Pipe + Socat and Remote Pipe + Socat the second is much 
slower. It can be concluded that the Pipe protocol is the fastest. This 
is logical because Pipe protocol is simpler than Remote protocol.

In connection with the above, I have a few questions.

Can someone of PowerDNS developers implement support for passing 
parameters to pipe:command and pipe-command? (example above)
Can someone of PowerDNS developers implement support for pipe protocol 
over unix socket? (as already implemented for remote protocol)

Regards,
Aleksey