On 19 February 2014 21:03, Philippe Mouawad <[email protected]> wrote: > On Wed, Feb 19, 2014 at 9:58 PM, sebb <[email protected]> wrote: > >> On 19 February 2014 18:49, sebb <[email protected]> wrote: >> > It looks as though the problem reported in Bug 56119 was due to the >> > server dropping connections that have been idle too long. >> > >> > There may also be servers that only allow a connection to be reused a >> > certain number of times (this does not seem to have been the case >> > here). >> > >> > This email is to discuss what JMeter could perhaps do to make it >> > easier to test such servers. >> > >> > The two existing work-rounds are: >> > - disable Keep-Alive >> > - enable staleCheck >> > >> > Neither is ideal; the first is awkward to use, and staleCheck can >> > generate unnecessary additional traffic (which is why it was disabled >> > in 2.11). >> > >> > I can think of two possible approaches: >> > >> > 1) proactively shut connections. This would be easy for servers that >> > limit reuse. >> > Just count reuses and turn off keep-alive when a specified limit is >> reached. >> > Not so easy for idle timeouts; one cannot retroactively disable >> keep-alive. >> > >> > 2) Deal with the disconnects when they occur. >> > The code needs to distinguish which errors are retriable, and may need >> > to distinguish at what point the failure occurs. For example, even a >> > POST ought to be retriable if JMeter is unable to send any data on the >> > connection. >> > >> > Also need to consider how one might report retries. >> > I think the tester needs to be able to find out if additional requests >> > have been made by JMeter. >> >> Further testing against the ASF servers shows that HC 4.2.x does >> handle idle timeouts without needing to use the staleCheck option. >> This relies on the server sending a header of the form: >> >> Keep-Alive: timeout=5, max=100 >> >> In this case, the connection is automatically recreated if necessary >> when the next sampler runs. >> If the server fails to send the header, then the connection may be >> dropped unexpectedly (which is what was happening with Bug 56119). >> So another approach might be to allow an optional keep-alive timeout >> in case the server does not provide one. >> >> Or we could take the view that there is nothing to fix in JMeter. >> The Keep-Alive header is there for a reason, it tells the client when >> it is safe to reuse the connectiion. >> If the server fails to send it, then it is broken, and so the failed >> samples are to be expected. >> > > I think we need to make something at least for servers like Amazon S3 which > close connections after number of uses. > Did you check to see if this kind of server send a keep alive header ?
I just tested again with jmeter.a.o. It returns headers of the form: Keep-Alive: timeout=5, max=100 Connection: Keep-Alive ... Keep-Alive: timeout=5, max=99 Connection: Keep-Alive ... etc ... Keep-Alive: timeout=5, max=1 Connection: Keep-Alive ... Connection: close So the HC connection manager does not need to keep track of the remaining re-use count; the server disconnects at the end of the last request. Nice and simple. I assume S3 does the same as jmeter.a.o if it is well-behaved. > Anyway on my side I think what has been changed in 2.11 should not be > reverted, because for servers correctly configured you don't get these > errors, I made 3 campaigns on different servers with 2.11 and never got > this kind of issues. Agreed, no need to revert. > But maybe we should document it better somewhere. Yes, the error and likely cause should be documented. Probably easiest to start as a Wiki page. > > > -- > Cordialement. > Philippe Mouawad.
