Remon,
As someone else (Phil Cogbill) pointed out earlier on another thread, you
can use Apache mod_limitipconn to place restrictions on max connections per
IP, etc. That was a nice write up - hi, Phil! ;-)
Another possibility to check is that Apache may not have enough slots
allocated to it. Check your server memory use with top and the MPM
directives section of httpd.conf for the values of ServerLimit and
MaxClients. If you change those you might want to do some profiling of
Apache's memory footprint first - ours showed (using top) VIRT memory usage
of 20-28MB and RES memory of 4-8MB per apache process. The output of "free
-mt" will give you an idea of total memory usage - but don't be fooled by
the value under "free" for "Mem:" which is calculated after the allocation
of RAM for I/O cache buffers (those get released as soon as there is a
request), so look for the number under the "free" column of the
"buffers/cache" line. That last number is what you can draw from to
increase Apache slots allocations, and the number to watch. The Apache
"ab" utility may be helpful for some of this, too.
And, this is re. Apache running on CentOS 5/6. Not sure about other
systems.
IHTH,
Georgi
On Fri, Sep 5, 2014 at 10:12 AM, Geir Aalberg <geira@xxxxxx> wrote:
> On 09/03/2014 05:29 PM, Remon Sadikni wrote:
>
> I just hoped to find a solution inside of the THREDDS config-file. To
>> somehow limit the simultaneous download of files...
>>
>
> As you yourself stated, the problem is this "slowed our Apache-Webserver
> down because its maximum count of incoming connections has been exceeded".
> You want to limit the amount of Apache connections, ergo you must limit the
> amount of Apache connections.
>
> By the time THREDDS is called it is already too late. All it can do is
> abort the transfer, but in most cases it will immediately have to deal with
> another one. What you want is for Apache (or a firewall/proxy) to filter
> out misbehaving IP addresses, keeping THREDDS free to deal with other
> customers.
>
> -geir
>
>
>
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--
Georgi Kostov
Team ERT/STG, US Government Contractor
NOAA National Climatic Data Center; NOMADS and NCMP
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