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Posted to users@tomcat.apache.org by Matthew Turany <mt...@anokii.com.au> on 2014/03/27 04:08:05 UTC
Is it possible to send a 'keep-alive' packet back to client session
every x seconds?
Hi,
Trying to figure out if this is possible; apache reverse-proxy sitting in
front of a server running tomcat serving a web app. Due to the amount of
data in the backend DB, when a user generated report is requested, it can
take several minutes (3-4) for the report to be presented to the browser
session.
In this particular case the client browser is sitting behind a gateway /
firewall that will drop the connection after 60 seconds of 'inactvity' e.g.
no traffic back to the browser (high-security environment).
The app presents a web pop-up stating "Your report is being prepared" and
session keepalive timeouts are all set accordingly, however since the
gateway doesn't see any active traffic it will close the connection forcing
the client browser to reconnect on a new connection which in affect loses
their report. (Note: that this all works fine for anyone not behind that
particular gateway)
Is it possible to configure either apache or tomcat to send a packet every
x number of seconds so that at the client end the gateway thinks the
session is still active and will keep the connection open, or is this
something best put into the actual web app?
Thanks,
Matt
Re: Is it possible to send a 'keep-alive' packet back to client session
every x seconds?
Posted by Frederik Nosi <fr...@postecom.it>.
Hi Matthew,
On 03/28/2014 01:35 AM, Matthew Turany wrote:
> Thanks everyone, development tells me that their going to build the
> function into the application.
You're lucky ;-)
> trying to build custom kernels and then using a tcp_keepalive would be a
> logistic nightmare.
I know you solved differently this issue, but in case other people is
watching this thread, who said you have to build custom kernels?!? Just
change a sysctl knob and be done with that. Exagerating, it's just ~100
characers to type, no reboot required neither. Check here for the
details, i'm sure will come handy in other situations:
http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/usingkeepalive.html
>
> Cheers,
> Matt
>
>
[...]
Frederik
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Re: Is it possible to send a 'keep-alive' packet back to client
session every x seconds?
Posted by Matthew Turany <mt...@anokii.com.au>.
Thanks everyone, development tells me that their going to build the
function into the application.
trying to build custom kernels and then using a tcp_keepalive would be a
logistic nightmare.
Cheers,
Matt
On Fri, Mar 28, 2014 at 12:53 AM, Christopher Schultz <
chris@christopherschultz.net> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> Mark,
>
> On 3/27/14, 5:38 AM, Mark Thomas wrote:
> > On 27/03/2014 03:08, Matthew Turany wrote:
> >> Is it possible to configure either apache or tomcat to send a
> >> packet every x number of seconds so that at the client end the
> >> gateway thinks the session is still active and will keep the
> >> connection open, or is this something best put into the actual
> >> web app?
> >
> > http://tomcat.apache.org/connectors-doc/reference/workers.html
> > socket_keepalive
> >
> > You'll need to configure the OS to send the packets frequently
> > enough.
> >
> > Alternatively, change the application design: - One request to
> > trigger generation of the report - N requests to retrieve report
> > which returns either "still processing" (maybe with an ETA) or
> > "here it is".
>
> +1
>
> I believe this is a better design in the long-run. It also allows you
> to do things like off-line processing of batches without changing your UI.
>
> Another thing you could do is simulate the above by using a
> report-builder thread launched from your servlet, and then have your
> request-processing thread to a flush() on the response (causing
> chunked encoding to be used), then sleep for some amount of time
> (maybe 1-5 seconds), then check the status of the report, then flush()
> again (not sure if it will keep emitting 0-length chunks if you flush
> over and over again), then sleep again.
>
> This seems like a perfect use case for async processing.
>
> - -chris
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> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
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>
Re: Is it possible to send a 'keep-alive' packet back to client session
every x seconds?
Posted by Christopher Schultz <ch...@christopherschultz.net>.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
Mark,
On 3/27/14, 5:38 AM, Mark Thomas wrote:
> On 27/03/2014 03:08, Matthew Turany wrote:
>> Is it possible to configure either apache or tomcat to send a
>> packet every x number of seconds so that at the client end the
>> gateway thinks the session is still active and will keep the
>> connection open, or is this something best put into the actual
>> web app?
>
> http://tomcat.apache.org/connectors-doc/reference/workers.html
> socket_keepalive
>
> You'll need to configure the OS to send the packets frequently
> enough.
>
> Alternatively, change the application design: - One request to
> trigger generation of the report - N requests to retrieve report
> which returns either "still processing" (maybe with an ETA) or
> "here it is".
+1
I believe this is a better design in the long-run. It also allows you
to do things like off-line processing of batches without changing your UI.
Another thing you could do is simulate the above by using a
report-builder thread launched from your servlet, and then have your
request-processing thread to a flush() on the response (causing
chunked encoding to be used), then sleep for some amount of time
(maybe 1-5 seconds), then check the status of the report, then flush()
again (not sure if it will keep emitting 0-length chunks if you flush
over and over again), then sleep again.
This seems like a perfect use case for async processing.
- -chris
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Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/
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Re: Is it possible to send a 'keep-alive' packet back to client session
every x seconds?
Posted by André Warnier <aw...@ice-sa.com>.
Mark Thomas wrote:
> On 27/03/2014 03:08, Matthew Turany wrote:
>> Is it possible to configure either apache or tomcat to send a packet every
>> x number of seconds so that at the client end the gateway thinks the
>> session is still active and will keep the connection open, or is this
>> something best put into the actual web app?
>
> http://tomcat.apache.org/connectors-doc/reference/workers.html
> socket_keepalive
>
> You'll need to configure the OS to send the packets frequently enough.
That's a bit the hammer, isn't it ? Under Linux at least, this seems to be a global kernel
setting, so it applies to all connections.
>
> Alternatively, change the application design:
> - One request to trigger generation of the report
> - N requests to retrieve report which returns either "still processing"
> (maybe with an ETA) or "here it is".
>
Apart from any gateways/proxies/firewalls, there is also a browser timeout : if the
browser sends a request, and then does not get a response for 4-5 minutes, eventually it
will time-out, close the connection, and display "the server is not responding.. try again
later".
Another possibility is to have the application periodically send some kind of "partial
response" to the browser (e.g., a line of ".."), to be replaced by the real response when
it's ready. It's a 20-year old trick, and it is a bit tricky to get right, but it still
works. Of course it means that the application has to be able to do that, and is not
itself waiting on a call to a slow external resource.
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Re: Is it possible to send a 'keep-alive' packet back to client session
every x seconds?
Posted by Mark Thomas <ma...@apache.org>.
On 27/03/2014 03:08, Matthew Turany wrote:
> Is it possible to configure either apache or tomcat to send a packet every
> x number of seconds so that at the client end the gateway thinks the
> session is still active and will keep the connection open, or is this
> something best put into the actual web app?
http://tomcat.apache.org/connectors-doc/reference/workers.html
socket_keepalive
You'll need to configure the OS to send the packets frequently enough.
Alternatively, change the application design:
- One request to trigger generation of the report
- N requests to retrieve report which returns either "still processing"
(maybe with an ETA) or "here it is".
Mark
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Re: Is it possible to send a 'keep-alive' packet back to client session
every x seconds?
Posted by Frederik Nosi <fr...@postecom.it>.
Hi,
On 03/27/2014 04:08 AM, Matthew Turany wrote:
> Hi,
>
> Trying to figure out if this is possible; apache reverse-proxy sitting in
> front of a server running tomcat serving a web app. Due to the amount of
> data in the backend DB, when a user generated report is requested, it can
> take several minutes (3-4) for the report to be presented to the browser
> session.
>
> In this particular case the client browser is sitting behind a gateway /
> firewall that will drop the connection after 60 seconds of 'inactvity' e.g.
> no traffic back to the browser (high-security environment).
> The app presents a web pop-up stating "Your report is being prepared" and
> session keepalive timeouts are all set accordingly, however since the
> gateway doesn't see any active traffic it will close the connection forcing
> the client browser to reconnect on a new connection which in affect loses
> their report. (Note: that this all works fine for anyone not behind that
> particular gateway)
>
> Is it possible to configure either apache or tomcat to send a packet every
> x number of seconds so that at the client end the gateway thinks the
> session is still active and will keep the connection open, or is this
> something best put into the actual web app?
The usual solution in this case is using Keepalive TCP. Check this, it's
based on Linux but
the theory works on every other OS:
http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/
> Thanks,
> Matt
>