We used the following configuration for the last contest.

Domserver Configuration Details 
Operating system : Ubuntu 12.04.5 LTS
domjudge version -5.0.1 
Apache/2.2.22 (Ubuntu)
mysql   5.5.47
RAM : 10 GB

Judgehost Configuration Details
Operating system : Ubuntu 12.04.5 LTS
RAM : 10 GB

We would be glad to know your recommendation for 400 users to connect also we can't be sure of submission at the last 10 minutes  of the contest and that we can't restrict submission 

Regards
Aneesh

On Wed, Aug 24, 2016 at 7:21 PM, Jaap Eldering <jaap@jaapeldering.nl> wrote:
On 24-08-16 05:47, Anand Shenoi wrote:
> Hi Jaap!
>
> Typical and common grammar issue :) Sorry for that!
>
> Precisely, it is the same scenario we had in the last regional. We
> started contest at 05:00 PM IST and in the first 5 minutes itself the
> submissions started queuing. We stopped in no time - since it was a
> testing contest.

Just from a quick glance, I see 454 judgings by judgehost1 in 1 hour.
That's 8 seconds per judging on average. Depending on the size of the
test cases that seems quite reasonable to me. So if these submissions
all came in at the first 5 minutes from 23 teams, then they are
overloading the system. There's not much you can do except adding more
judgehosts or telling teams not to do this.

Jaap


> On Tue, Aug 23, 2016 at 6:00 PM Jaap Eldering <jaap@jaapeldering.nl
> <mailto:jaap@jaapeldering.nl>> wrote:
>
>     Hi Aneesh,
>
>     On 23-08-16 02:13, Aneesh R wrote:
>     > Hi,
>     >
>     > On August 22nd at 17:00 IST to 18:00 IST we had conducted a practice
>     > session with our local  domjudge server , this is only testing the
>     > potential of our domjudge server and used only one judgehost for this
>     > session.  Two sets of problems are included in this session, the
>     > solutions are already shared with our students (23 users)
>
>     From here on I find it difficult to understand precisely what happened:
>
>     > they are continually submitting the solutions when the
>     > contest starts  woefully the all submissions are going to the
>     QUEUED and
>     > the compilations are in PENDING , then we are announced to
>     > all students to stop their submissions and they can logout by
>     17:30 IST
>     > and we are waiting to finish all the pending submissions it take
>     around
>     > 18:10 IST
>
>     Could you explain again step by step what _actually_ happened and what
>     you _expected_ to happen? Preferably do so in short sentences.
>
>     Best,
>     Jaap
>
>
>     > We don't know what's happening on the server . So we are attaching the
>     > server logs with this mail kindly verify and suggest me some solutions
>     >
>     > Regards
>     > Aneesh
>