[ovirt-users] Tunable parameters in ovirt engine

Wed Mar 7 15:50:50 UTC 2018

It means that with the default configuration the Apache web server can't 
serve more than 256 concurrent connections. This applies to any 
application that uses Apache as the web frontend, not just to oVirt. If 
you want to change that you have to change the MaxRequestWorkers and 
ServerLimit parameters, as explained here:

   https://httpd.apache.org/docs/2.4/mod/mpm_common.html#maxrequestworkers

So, go to your oVirt engine machine and create a 
/etc/httpd/conf.d/my.conf file with this content:

   MaxRequestWorkers 1000
   ServerLimit 1000

Then restart the Apache server:

   # systemctl restart httpd

Then your web server should be able to handle 1000 concurrent requests, 
and you will probably start to find other limits, like the amount of 
memory and CPU that those 1000 Apache child processes will consume, the 
number of threads in the JBoss application server, the number of 
connections to the database, etc.

Let me insist a bit that if you base your benchmark solely on the number 
of concurrent requests or connections that the server can handle you may 
end up with meaningless results, as a real world application can/should 
use the server much better than that.

On 03/07/2018 04:33 PM, Hari Prasanth Loganathan wrote:
> With the default configuration of the web server it is impossible to handle
> more than 256 *connections* simultaneously. I guess that "ab" is opening a
> connection for each concurrent request, so when you reach request 257 the
> web server will just reject the connection, there is nothing that the JBoss
> can do about it; you have to increase the number of connections supported
> by the web server.
> 
> *So Does it mean that oVirt cannot serve more than 257 request? *
> My question is, If its possible How to scale this and what is the
> configuration we need to change?
> 
> Also, we are taking a benchmark in using oVirt, So I need to find the
> maximum possible oVirt request. So please let me know the configuration
> tuning for oVirt to achieve maximum concurrent request.
> 
> Thanks,
> Hari
> 
> On Wed, Mar 7, 2018 at 7:25 PM, Juan Hernández <jhernand at redhat.com> wrote:
> 
>> With the default configuration of the web server it is impossible to
>> handle more than 256 *connections* simultaneously. I guess that "ab" is
>> opening a connection for each concurrent request, so when you reach request
>> 257 the web server will just reject the connection, there is nothing that
>> the JBoss can do about it; you have to increase the number of connections
>> supported by the web server.
>>
>> Or else you may want to re-consider why you want to use 1000 simultaneous
>> connections. It may be OK for a performance test, but there are better ways
>> to squeeze performance. For example, you could consider using HTTP
>> pipelining, which is much more friendly for the server than so many
>> connections. This is what we use when we need to send a large number of
>> requests from other systems. There are examples of how to do that with the
>> Python and Ruby SDKs here:
>>
>>    Python:
>>
>> https://github.com/oVirt/ovirt-engine-sdk/blob/master/sdk/
>> examples/asynchronous_inventory.py
>>
>>    Ruby:
>>
>> https://github.com/oVirt/ovirt-engine-sdk-ruby/blob/master/
>> sdk/examples/asynchronous_inventory.rb
>>
>>
>> On 03/07/2018 02:43 PM, Hari Prasanth Loganathan wrote:
>>
>>> Hi Juan,
>>>
>>> Thanks for the response.
>>>
>>> I agree web server can handle only limited number of concurrent requests.
>>> But Why it is failing with SSL handshake failure for few requests, Can't
>>> the JBOSS wait and serve the request? We can spare the delay but not with
>>> the request fails. So Is there a configuration in oVirt which can be tuned
>>> to achieve this?
>>>
>>> Thanks,
>>> Hari
>>>
>>> On Wed, Mar 7, 2018 at 7:05 PM, Juan Hernández <jhernand at redhat.com>
>>> wrote:
>>>
>>> The first thing you will need to change for such a test is the number of
>>>> simultaneous connections accepted by the Apache web server: by default
>>>> the
>>>> max is 256. See the Apache documentation here:
>>>>
>>>>     https://httpd.apache.org/docs/2.4/mod/mpm_common.html#m
>>>> axrequestworkers
>>>>
>>>> In addition I also suggest that you consider using the "worker"
>>>> multi-processing module instead of the "prefork", as it usually works
>>>> better when talking to a Java application server, because it re-uses
>>>> connections better.
>>>>
>>>> On 03/07/2018 02:20 PM, Hari Prasanth Loganathan wrote:
>>>>
>>>> Hi Team,
>>>>>
>>>>> *Description of problem:*
>>>>>
>>>>> I am trying to achieve 1000 concurrent request to oVirt. What are the
>>>>> tunable parameters to achieve this?
>>>>>
>>>>> I tried to perform the benchmarking for ovirt engine using Apache
>>>>> benchmark
>>>>> using the same SSO token.
>>>>>
>>>>> ab -n 1000 -c 500 -k -H "accept: application/json" -H "Authorization:
>>>>> Bearer SSOTOKEN" https://172.30.56.70/ovirt-engine/
>>>>> <https://172.30.56.70/ovirt-engine/api/vms/5440271b-afb3-48b
>>>>> b-9ff1-076fc07ebf50/statistics>
>>>>>
>>>>> When the number of concurrent request is 500, we are getting more than
>>>>> 100
>>>>> failures with the following error,
>>>>>
>>>>> SSL read failed (1) - closing connection
>>>>> 139620982339352:error:
>>>>>
>>>>> NOTE: It is scaling for concurrent request below 500.
>>>>>
>>>>> I used the profiler to get the memory and CPU and it seems very less,
>>>>>
>>>>>      PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+
>>>>> COMMAND
>>>>> 30413 ovirt     20   0 4226664 882396   6776 S 126.0 23.0  27:48.53 java
>>>>>
>>>>> Configuration of the machine in which Ovirt is deployed :
>>>>>
>>>>> RAM - 4GB,
>>>>> Hard disk - 100GB,
>>>>> core processor - 2,
>>>>> OS - Cent7.x.
>>>>>
>>>>> In which 2GB is allocated to oVirt.
>>>>>
>>>>>
>>>>> Version-Release number of selected component (if applicable):
>>>>>
>>>>> 4.2.2
>>>>>
>>>>>
>>>>> How reproducible:
>>>>>
>>>>> If the number of concurrent requests are above 500, we are easily facing
>>>>> this issue.
>>>>>
>>>>>
>>>>> *Actual results:*
>>>>>
>>>>> SSL read failed (1) - closing connection
>>>>> 139620982339352:error:
>>>>>
>>>>> *Expected results:*
>>>>>
>>>>> Request success.
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Hari
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Users mailing list
>>>>> Users at ovirt.org
>>>>> http://lists.ovirt.org/mailman/listinfo/users
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
> 