bbtest shows long DNS runtime, why

[thorsten.erdmann (at) daimler.com]

Hi

I am running hobbit against 40 clients. Two of these clients are our DNS 
servers. Only on these two clients I have enabled the DNS test by adding 
the DNS keyword to their bb-hosts line. I wanted to check the function of 
the DNS servers

If I look at the statistics of bbtest it looks like this:

Fri Sep 12 15:26:08 2008

bbtest-net version 4.2.0
SSL library : OpenSSL 0.9.7a Feb 19 2003
LDAP library: OpenLDAP 20213

Statistics:
 Hosts total           :       41
 Hosts with no tests   :        1
 Total test count      :       44
 Status messages       :       45
 Alert status msgs     :        0
 Transmissions         :        2

DNS statistics:
 # hostnames resolved  :       40
 # succesful           :       40
 # failed              :        0
 # calls to dnsresolve :       44

TCP test statistics:
 # TCP tests total     :        2
 # HTTP tests          :        1
 # Simple TCP tests    :        1
 # Connection attempts :        2
 # bytes written       :      126
 # bytes read          :      871


TIME SPENT
Event                                            Starttime Duration
bbtest-net startup                       1221225968.275331 -
Service definitions loaded               1221225968.276931 0.001600 
Tests loaded                             1221225968.281365 0.004434 
DNS lookups completed                    1221225973.283037 5.001672 
Test engine setup completed              1221225973.285332 0.002295 
TCP tests completed                      1221225973.286398 0.001066 
PING test completed (40 hosts)           1221225974.166549 0.880151 
PING test results sent                   1221225974.177932 0.011383 
Test result collection completed         1221225974.177943 0.000011 
LDAP test engine setup completed         1221225974.177944 0.000001 
LDAP tests executed                      1221225974.177945 0.000001 
LDAP tests result collection completed   1221225974.177946 0.000001 
NSLOOKUP tests executed                  1221225974.179452 0.001506 
Test results transmitted                 1221225974.181039 0.001587 
bbtest-net completed                     1221225974.182936 0.001897 
TIME TOTAL 5.907605 


What you see are two mystic things:

It seems that hobbit resolves all clients via DNS:   
  # hostnames resolved  :       40
Why that, I gave all names and it's corresponding IPs at the bb-hosts 
file?

The DNS test runs about 5 seconds for only these 40 clients, maybe that is 
because of the first issue: 
  DNS lookups completed                    1221225973.283037 5.001672

If you look at the graph, it gives very scary "triagle curves". I've put a 
screenshot here: http://www.trektech.de/test/hobbitgraph.png
The thing seems to have started when I put the DNS keyword to my two DNS 
servers. Before it gave a nearly zero line.

I want to add about 400 network switches which should only do a ping test 
and I fear that this would extremely increase the runtime of the bbtest.
What can I do to decrease the runtime?

Thorsten Erdmann
ITI/EP68
Mercedes Benz Werk Hamburg
Tel.: +49-40-7920-2593



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