[SR-Users] dispatcher algorithm 11, no more than 25 hosts in group for proper distribution

Wed Mar 31 17:25:54 CEST 2021

Hello Daniel

Yes, it was clear to me, why my TT was closed.
Apologise for not starting with the mailing list.

Regarding algorithm 11.
Yes, you are right.
To sum up, if you want to have equal call distribution, the number of
hosts must provide integer value when 100 is divided by it.
Thus, the number of hosts permitting equal call distribution is: 1, 2,
4, 5, 10, 20, 25, 50, 100.

With best regards
Ivan

On Tue, Mar 30, 2021 at 9:36 PM Daniel-Constantin Mierla
<miconda at gmail.com> wrote:
>
> Hello,
>
> there was an issue on the tracker, but this looks like the redistribution due to percentage not being an integer number.  I referred to the docs (being noted there), closed the issue and pointed to sr-users for further discussions.
>
> So, for example, if there are 30 routes each with rweight of 50, that means total rweight of 1500. With that, each route has the percentage of 50*100/1500=3.33, which is rounded to 3, meaning that each destination gets 3 calls in 100, total 90, with the last one (which can be the first in the dispatcher list file, depending on internal sorting and instert) getting the remaining 10, overall 13 go to this route (so 19 routes will get 3 calls, and 1 will get 13 calls). Now, depending on the number of routes, one of them may get a different value, but the fact is that if the percentage isn't an integer number, then the distribution is not equal for one of them. For example, with the 6 routes:
>
> total rweight => 6 * 50 = 300; then percentage per route is 50*100/300 = 16.6, rounded to 16, meaning one will get 20.
>
> You may want to do a double check of the rweight algorithm code, I haven't implemented it, but for weight the above remarks apply.
>
> That was discussed in the past on the mailing list, and very likely it is not a bug also in this case, but how the distribution can be spread across 100 calls.
>
> Even more, for r/weight algorithms, it really makes no sense to use them when there are so many routes with same weight, practically on more than 50, each one will get 1 call and the last in the memory least will get 51. So one gets more than 50% of the calls. From the other perspective, this is not even feasible to route to all of them in the same step, because by default kamailio can create 12 branches for a request, with a maximum configurable value of 31 (iirc). I think round robin or call load distribution is better for such large number of routes.
>
> Cheers,
> Daniel
>
> On 30.03.21 18:57, Julien Chavanton wrote:
>
> Hi Ivan, must be a limitation/problem in the computation, can you open an issue.
>
> Since I have built on top of algorithm 11, I could have a look, we may also notify the original author to see what can be done.
>
> On Tue, Mar 30, 2021 at 8:52 AM Ivan Matvieiev <i.matvieiev at kwebbl.com> wrote:
>>
>> Hello Community,
>>
>> There is a module dispatcher and sharing algorithm 11 that features
>> the ability to redistribute load when the host is enabled or disabled
>> that is quite valuable for me.
>> In the test lab I faced unexpected behavior:
>> - when I add to group <=25 hosts algorithm behaves as per description.
>> - when a group includes 26 or more hosts, and 100 calls are done for
>> instance, then about 25 go to the first host and 75 are distributed
>> among the rest of hosts.
>>
>> Expected behavior: all hosts of the group having the same rweight
>> value must receive the same amount of calls no mater what number of
>> hosts is in the group.
>>
>> Could you please to help to figure out what is wrong and why when the
>> dispatcher group consists of 26+ hosts dispatching algorithm 11
>> behaves differently than when group consists of 25 or less of hosts?
>>
>> Some configuration notes:
>> # module configs
>> modparam("dispatcher", "list_file", "/etc/kamailio/dispatcher.list")
>> modparam("dispatcher", "flags", 2)
>> modparam("dispatcher", "ds_ping_method", "OPTIONS")
>> modparam("dispatcher", "ds_probing_threshold", 3)
>> modparam("dispatcher", "ds_inactive_threshold", 10)
>> modparam("dispatcher", "ds_probing_mode", 3)
>> modparam("dispatcher", "ds_ping_interval", 10)
>> modparam("dispatcher", "ds_ping_reply_codes", "501,403,404,400,200")
>> modparam("dispatcher", "ds_ping_from",DS_PING_FROM_PARAM)
>> modparam("dispatcher", "use_default", 0)
>>
>> # dispatching algorithm call
>> if ( ds_is_from_list("101")) {
>>      sl_send_reply("100","My calls");
>>      ds_select_dst("100", "11");
>>      return;
>> }
>>
>> # dispatcher list group config
>> 100 sip:10.60.27.123:7000 0 10 rweight=50
>> 100 sip:10.60.27.123:7001 0 10 rweight=50
>> 100 sip:10.60.27.123:7002 0 10 rweight=50
>> 100 sip:10.60.27.123:7003 0 10 rweight=50
>> 100 sip:10.60.27.123:7004 0 10 rweight=50
>> 100 sip:10.60.27.123:7005 0 10 rweight=50
>> 100 sip:10.60.27.123:7006 0 10 rweight=50
>> 100 sip:10.60.27.123:7007 0 10 rweight=50
>> 100 sip:10.60.27.123:7008 0 10 rweight=50
>> 100 sip:10.60.27.123:7009 0 10 rweight=50
>> 100 sip:10.60.27.123:7010 0 10 rweight=50
>> 100 sip:10.60.27.123:7011 0 10 rweight=50
>> 100 sip:10.60.27.123:7012 0 10 rweight=50
>> 100 sip:10.60.27.123:7013 0 10 rweight=50
>> 100 sip:10.60.27.123:7014 0 10 rweight=50
>> 100 sip:10.60.27.123:7015 0 10 rweight=50
>> 100 sip:10.60.27.123:7016 0 10 rweight=50
>> 100 sip:10.60.27.123:7017 0 10 rweight=50
>> 100 sip:10.60.27.123:7018 0 10 rweight=50
>> 100 sip:10.60.27.123:7019 0 10 rweight=50
>> 100 sip:10.60.27.123:7020 0 10 rweight=50
>> 100 sip:10.60.27.123:7021 0 10 rweight=50
>> 100 sip:10.60.27.123:7022 0 10 rweight=50
>> 100 sip:10.60.27.123:7023 0 10 rweight=50
>> 100 sip:10.60.27.123:7024 0 10 rweight=50
>>
>> Kamailio version:
>> kamailio -v
>> version: kamailio 5.4.4 (x86_64/linux) e16352
>> flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS,
>> DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC,
>> F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX,
>> FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR,
>> USE_DST_BLACKLIST, HAVE_RESOLV_RES
>> ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_URI_SIZE
>> 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB
>> poll method support: poll, epoll_lt, epoll_et, sigio_rt, select.
>> id: e16352
>> compiled on 15:56:46 Feb 15 2021 with gcc 4.8.5
>>
>> System info
>> CentOS Linux release 7.7.1908 (Core)
>> Linux test-carrier-1.loc 3.10.0-1062.4.1.el7.x86_64 #1 SMP Fri Oct 18
>> 17:15:30 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
>>
>> _______________________________________________
>> Kamailio (SER) - Users Mailing List
>> sr-users at lists.kamailio.org
>> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
>
>
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> --
> Daniel-Constantin Mierla -- www.asipto.com
> www.twitter.com/miconda -- www.linkedin.com/in/miconda
> Funding: https://www.paypal.me/dcmierla
>
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