[Tsung] Re: postgresql testing - authentication / phases / open connections

[Michael Nacos]

minor corrections to the questions:

sorry, I was wrong when I said I didn't see anything different when I
switched pg connect model from md5 to password - I was looking at the wrong
graphs. So the password model works - does tsung also support md5?

and yes, the remote test with password (not md5) authentication has worked
like a charm - very happy.

but the questions regarding the local server (testing client - tested server
were the same machine) remain.
and what is page in the graphs?

Michael

On Fri, Jul 4, 2008 at 12:55 PM, Michael Nacos <m.nacos at gmail.com> wrote:

> Hello to everyone.
>
> <some background>
>
> I am a total Erlang newbie (I-have-written-a-little-bit-of-demo-code level)
> but I am falling in love with the language.
> I have also just started a new job, as Postgresql DBA and Tsung may just be
> my big Erlang break:
> My company has serious load testing needs, Tsung is exactly what they
> couldn't find before, it's got a postgres module,
> and a big part of my job will be scalability tests, so Tsung might just be
> my ticket to programming Erlang professionally
> (they will probably be very happy if I come up with some Erlang code for
> test case randomization or other cool things)
> And, by the way, I really enjoyed the Erlang Exchange. Thanks, guys.
>
> </some background>
>
> I have been trying to load test one of our development Postgres servers,
> using a very simple setup (no distribution/
> coordination of multiple machines). Now, the results I get if I run my test
> scenario on the actual db server present
> some qualitative differences compared to the results I get if the tests
> originate on another machine connecting through
> port 5432 (-- I am using the same tsung.xml file in both cases, of course)
>
> The total size_sent (kbits) lines in both cases match the relevant patterns
> in the users arrival graph. The size_rcv lines
> are not consistent, though. In the local test, the size_rcv line linearly
> grows up to 100 users (simultaneous) then becomes
> horizontal - which may have something to do with the default postgres
> setting for 100 max_connections. Does this mean
> the same original 100 connections are maintained throughout the test, even
> after the queries have finished, so there is no
> more data coming in?
>
> The size_rcv line for the remote test, however, always stays very near
> zero. Now, the total errors graph matches exactly the
> total user arrival graph, so I am kind of assuming something is going
> horribly wrong with the remote queries (users
> send by don't receive).
>
> Now, I have tried to run the following line in both machines (local and
> remote, where local is the server) and it works
> fine in both cases. The only difference is I am using the trust model for
> local pg connections (so I don't get asked for
> a password when I run this on the server) and the md5 model for remote pg
> connections (so I get asked for a password
> when I run this on the remote machine) - I am assuming this is an
> authentication problem, then.
>
> cat test.sql | psql -U user -h localhost -p 5432 database
>
> I have also tried to change the model for remote pg connections to password
> (clear text over the net, bad idea), but I
> get exactly the same behaviour. Is there something broken with tsung's
> authentication mechanism, or is there something
> wrong in my xml file:
>
>     <transaction name="connection">
>         <request>
>            <pgsql type="connect" database="database" username="user" />
>         </request>
>     </transaction>
>
>     <request><pgsql type="authenticate" password="pass"/></request>
>
> Another thing concerns arrival phases:
>
> I have specified three arrival phases in the xml file, a fast one followed
> by a slow one, followed by a fast one (this
> doesn't need to make sense, I am just experimenting with the software).
> Tests from the local machine show an
> expected ladder-like pattern when it comes to the
> graphes-Users_Arrival-total graph, tests from the remote machine
> don't (it's quite linear). Similar patterns may be observed in the total
> kbits size_sent graphs and the total errors graphs,
> so I think for some reason user arrival doesn't go as planned in the remote
> test box case. Any ideas?
>
> There is also the matter of finished users in the local test. For some
> reason, those 100 users which are able to
> connect don't seem to finish. In fact, there is a constant difference of
> about 100 users between users_count and
> finish_users_count throughout the graph, start to finish.
> The number of simultaneous connections which remain after the end of the
> experiment confirms this.
> Should this happen, considering I have included the following line in
> tsung.xml?
>
>     <request><pgsql type="close"></pgsql></request>
>
> Finally, in the transaction graphs I also get something called page (which,
> by the way, is huge - its mean value
> reaches 60000 msec at some stages).
>
> Any help will be appreciated...
>
> Michael
>
>
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