[SR-Users] Dispatcher Confusion (v3.2.0)
Daniel-Constantin Mierla
miconda at gmail.com
Tue Oct 25 17:30:56 CEST 2011
Hello,
the probing state is no longer related to selection of the gateways. It
is unclear in the previous version what is the role of it in selection
of an address, since some time, a gw in probing was wanted to be
selected and some time not.
So probing is a state related to whether to send or not keepalive to a
gw. If you don't want a gateways to be selected, it has to be inactive
or disabled. One may want active gateways to be in probing mode to
detect quickly when it is down with keepalives.
If the documentation has some old content in some places, has to be
updated -- maybe you can send the patch if you spotted the confusing parts.
Cheers,
Daniel
On 10/25/11 4:11 PM, Asgaroth wrote:
> Hi All,
>
> Just wondering, has anyone else experienced the behaviour described
> below, where messages are still routed to a gateway that is in
> Active-Probing state? From my understanding of the docs, when a
> destination is in probing state, it should not be used in the
> destination selection. I can see that Kamailio does set the state from
> AX to AP (Active to Active-Probing) when a timeout occurs, and a
> "kamctl dispatcher dump" does show that the state has changed to AP,
> however, sip trace to the destination still shows messages being
> routed to the destination that is in AP mode.
>
> Just checking if anyone else is seeing this behaviour as well.
>
> Thanks
>
>
> On 24/10/2011 16:30, Asgaroth wrote:
>> OK, did a few more tests but have come accross something, which I am
>> not sure is intended behaviour.
>>
>> When setting a destingation as probing in failure route (due to
>> timeout), the destination still gets used in destination selection.
>>
>> # ./kamailio -V
>> version: kamailio 3.3.0-dev0 (i386/linux) 25bedc
>> flags: STATS: Off, USE_IPV6, USE_TCP, USE_TLS, TLS_HOOKS,
>> USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MEM,
>> SHM_MMAP, PKG_MALLOC, DBG_QM_MALLOC, 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_LISTEN 16,
>> MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 4MB
>> poll method support: poll, epoll_lt, epoll_et, sigio_rt, select.
>> id: 25bedc
>> compiled on 09:18:41 Oct 21 2011 with gcc 4.1.2
>>
>> Dispatcher module parameters (in testing) are as follows
>> (SBC_PING_FROM is #defined previously):
>>
>> modparam("dispatcher", "flags", 2)
>> modparam("dispatcher", "dst_avp", "$avp(AVP_DST)")
>> modparam("dispatcher", "grp_avp", "$avp(AVP_GRP)")
>> modparam("dispatcher", "cnt_avp", "$avp(AVP_CNT)")
>> modparam("dispatcher", "ds_ping_method", "OPTIONS")
>> modparam("dispatcher", "ds_ping_from", SBC_PING_FROM)
>> modparam("dispatcher", "ds_ping_interval", 10)
>> modparam("dispatcher", "ds_probing_threshhold", 1)
>> modparam("dispatcher", "ds_probing_mode", 0)
>>
>> Main routing logic has following snippet to select destination (hash
>> table selects dispatcher setid based on request domain):
>>
>> if(!ds_select_dst("$sht(which_sbc=>$rd)", "0")) {
>> sl_send_reply("500", "No destination available");
>> xlog("route[MAIN] : $rm : No destinations
>> available for $rd");
>> exit;
>> }
>>
>> Failure route has following logic to select next destination based on
>> timout/failure of destination:
>>
>> if (t_branch_timeout() && !t_branch_replied())
>> {
>> xlog("route[TO_SBC] : $rm : timeout and no reply
>> ($si:$sp->$Ri:$Rp->$du)\n");
>> xlog("route[TO_SBC] : $rm : setting $du to probing
>> state");
>> ds_mark_dst("p");
>> if(ds_next_dst())
>> {
>> xlog("route[TO_SBC] : $rm : next destination
>> select ($du)\n");
>> t_on_failure("TO_SBC");
>> t_relay();
>> exit;
>> } else {
>> send_reply("500", "No destination available");
>> xlog("route[TO_SBC] : $rm : No destinations
>> available for $rd");
>> exit;
>> }
>> }
>>
>> According to 3.2 module docs for dispatcher, when a destination is
>> set into probing state, it will not be used by ds_select_dst:
>> ----
>>
>>
>> 4.6. |ds_mark_dst("s")|
>>
>> Mark the last used address from destination set as inactive
>> ("i"/"I"/"0"), active ("a"/"A"/"1") or probing ("p"/"P"/"2"). With
>> this function, an automatic detection of failed gateways can be
>> implemented. When an address is marked as inactive or probing, it
>> will be ignored by 'ds_select_dst' and 'ds_select_domain'.
>>
>> possible parameters:
>>
>> *
>>
>> /"i", "I" or "0"/ - the last destination should be set to
>> inactive and will be ignored in future requests.
>>
>> *
>>
>> /"a", "A" or "1"/ - the last destination should be set to active
>> and the error-counter should set to "0".
>>
>> *
>>
>> /"p", "P" or "2"/ - the last destination will be set to probing.
>> Note: You will need to call this function "threshhold"-times,
>> before it will be actually set to probing.
>>
>> This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.
>>
>> ---
>>
>> What happens here, for me, is:
>>
>> [1] Gateway is in Active mode (state: AX).
>> [2] Request comes in and times out, destination is set to
>> Active/Probing (state: AP)
>> [3] Another request comes in and it selects gateway that is in AP
>> mode, times out, and then selects next dst in list.
>> [4] Another request comes in and it selects gateway that is in AP
>> mode, times out, and then selects next dst in list.
>> .
>> .
>>
>> NOTE: The requests selecting the AP mode gateway may not be right
>> after each other (algorythm used is hash over callid) but I have
>> stripped those out in above steps. If I'm not mistaked, if 2
>> destination in a set, and 1 destination is marked as AP, then
>> remaining destination should always be selected as destination to
>> send to. The destination marked AP (active-probing) should not be
>> selected while in probing state.
>>
>> When the gateway is set into AP mode at step [2], then, according to
>> docs, any new request coming in should not have the gateway selected
>> as it is marked as being in probing state.
>>
>> Is this the intended behaviour or am I missing something in the
>> documentation, or is it a bug?
>>
>> Thanks
>>
>> [...]
--
Daniel-Constantin Mierla -- http://www.asipto.com
Kamailio Advanced Training, Dec 5-8, Berlin: http://asipto.com/u/kat
http://linkedin.com/in/miconda -- http://twitter.com/miconda
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