<div dir="ltr"><div>Hello Daniel,</div><div><br></div><div>Thanks for the input. That clears it up.</div><div><br></div><div>@Ben Merrills: Glad to hear my rants are useful to other people as well :-). Branches are indeed among the more complicated concepts in kamailio scripting. I've always found resources that explain how things work much more useful than "how-to/examples" approaches to documentation when it comes to producing real-world configurations (Daniel and Ramona's kamailio ebook is a good starting point if you're struggling with grasping the larger picture). Maybe in part because I can't settle with something just working the way a set of requirements expect it to unless I also understand the why.</div><div><br></div><div>BR,</div><div>George<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, 22 Jan 2020 at 10:35, Daniel-Constantin Mierla <<a href="mailto:miconda@gmail.com">miconda@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p>Hello,</p>
<p>a new branch is created every time a request is sent out to a new
destination or resent to same destination after additional
processing in a failure route. append_branch() should not be
needed, unless you want to create more branches for parallel
forking. Updating $ru or $du and doing t_relay() in failure route
should be all what is needed to send to a new branch.</p>
<p>To have branch route execution, be sure you set it before
t_relay(), also in failure route, even if you set it previously in
request_route for first branch -- in other words, t_on_branch()
must be used for each step of serial forking.</p>
<p>The branch route block is executed inside t_relay(), so it is in
the same process that sends out the request, but in case of
failure routing, further branches are not created in the same
process as the first branch. The best is to use $xavp/$avp if you
are not sure where and when those branch processing happen.</p>
<p>Cheers,<br>
Daniel<br>
</p>
<div>On 21.01.20 23:22, George
Diamantopoulos wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>Hello all,</div>
<div><br>
</div>
<div>Some keyboard shortcut resulted in gmail previously sending
the message out before I had finished writing it, sorry about
that. This is the complete message.</div>
<div><br>
</div>
<div>I'm trying to accomplish the following scenario, and some
questions have arisen during testing: I'd like to be able to
fork serially to a number of downstream destinations in case
of failure, but also try several hosts which are available per
destination network (via dispatcher module) before failing
over to the next one (e.g. try two gateways for provider A and
if both fail, then try two more gateways for provider B etc).
I also need to perform some network-specific handling per
destination group (=provider), which I thought I'd perform in
respective branch routes. To that end, I'm using something
similar to the config pasted toward the end of the message.</div>
<div><br>
</div>
<div>Here's some points that have troubled me, if anyone can
provide some insight:</div>
<div>
<ol>
<li>After exhausting dispatcher group entries for
first_provider, the request is indeed forwarded to
last_provider with this configuration. I've noticed a new
branch is created. I'm assuming this happens because
there's some RURI manipulation taking place in
branch_route? I recall reading somewhere that even doing
$ru = $ru will result in a new branch being created. Is my
assumption correct here, or is the new branch created for
some other reason? I mean if I did t_on_branch in a
failure route following a t_relay which failed, but
without manipulating the RURI in the new branch_route,
would that still create an implicit new branch or would
one have to use append_branch() or similar in this case?</li>
<ul>
<li>I'm asking because several implicit or explicit branch
creation mechanisms are documented in various places
(e.g. usrloc, lcr, alias_db, corex) but it's there's no
comprehensive list for reference.<br>
</li>
</ul>
<li>If there are two destinations in the destination group
for first_provider, and the first one fails, then the
second destination will be tried out in
tm:branch-failure:DISPATCH_FIRST_PROV_FAILOVER. Now the
Via branch parameter for this INVITE is different than the
original (.1 instead of .0), which one can verify by
capturing the traffic on-net. However, in the logs, the
respective branch route is only run once, and there's no
reference to the ".1" Via, even with cfg script debugging
enabled. I'm assuming this means that kamailio's
definition of "branch" in the context of the configuration
file is different to the notion of branch as a transaction
identifier in SIP signalling in general? In simpler
language, distinct branch identifiers in Via headers
between two requests does not mean that these two requests
were treated as separate branches in kamailio config: true
or false?<br>
</li>
<li>This is causing the most problems for me right now: the
$vn PVs seem to be available for the first (main?) branch,
but not for subsequent branches which are generated if the
first branch fails. I was under the impression that
branch_routes are handled by the same process as the
request_route for a message, and as a consequence I was
expecting private variables to be available there. This
doesn't seem to be the case with the example configuration
below. $vn(some_var) in branch_route[LAST_PROV_BRANCH]
evaluates to NULL. Any insight as to why this happens? And
if I need these vars to be available in serial forking, is
the recommended solution to use shared variables or is my
approach here problematic in other ways?</li>
</ol>
<div>Thanks!</div>
<div>George<br>
</div>
</div>
<div><br>
</div>
<div><span style="font-family:monospace">request_route {</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">...</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">$vn(some_var) = "some_value";</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">$vn(some_other_var) =
"some_other_value";</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">...</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">$avp(provider_order) =
"last_provider";</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">$avp(provider_order) =
"first_provider";</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">...</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">t_set_fr(120000, 2000);</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">route(PROVIDER_SELECTION);</span></div>
<div><span style="font-family:monospace">}</span></div>
<div><span style="font-family:monospace"><br>
</span></div>
<div><span style="font-family:monospace">route[PROVIDER_SELECTION]
{</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">if (
is_avp_set("$avp(provider_order)") ) {</span></div>
<div style="margin-left:80px"><span style="font-family:monospace">t_on_failure("PROVIDER_SERIAL");</span></div>
<div style="margin-left:80px"><span style="font-family:monospace">if ( $avp(provider_order) ==
"first_provider" ) {</span></div>
<div style="margin-left:120px"><span style="font-family:monospace">$avp(provider_order) = $null;</span></div>
<div style="margin-left:120px"><span style="font-family:monospace">route(DISPATCH_FIRST_PROV);</span></div>
<div style="margin-left:80px"><span style="font-family:monospace">} else if (
$avp(provider_order) == "last_provider" ) {</span></div>
<div>
<div style="margin-left:120px"><span style="font-family:monospace">$avp(provider_order) =
$null;</span></div>
<div style="margin-left:120px"><span style="font-family:monospace">route(DISPATCH_LAST_PROV);</span></div>
<div style="margin-left:80px"><span style="font-family:monospace">}<br>
</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">}<br>
</span></div>
<div><span style="font-family:monospace">}</span></div>
<div><span style="font-family:monospace"><br>
</span></div>
<div><span style="font-family:monospace">route[DISPATCH_FIRST_PROV]
{<br>
</span>
<div style="margin-left:40px"><span style="font-family:monospace">if ( !ds_select_dst("1",
"4") ) {<br>
</span></div>
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">if (
is_avp_set("$avp(provider_order)") ) {<br>
</span></div>
</div>
<div style="margin-left:40px">
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">route(PROVIDER_SELECTION);<br>
</span></div>
</div>
</div>
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">} else {<br>
</span></div>
</div>
<div style="margin-left:40px">
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">t_send_reply("503",
"Downstream carrier unavailable");<br>
</span></div>
</div>
</div>
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">}<br>
</span></div>
</div>
<div style="margin-left:40px"><span style="font-family:monospace">}<br>
<br>
t_on_branch_failure("DISPATCH_FIRST_PROV_FAILOVER");<br>
t_on_branch("FIRST_PROV_BRANCH");<br>
<br>
route(RELAY);<br>
exit;<br>
</span></div>
<span style="font-family:monospace">}</span></div>
<div><span style="font-family:monospace"><br>
</span></div>
<div><span style="font-family:monospace">route[DISPATCH_LAST_PROV]
{<br>
</span>
<div style="margin-left:40px"><span style="font-family:monospace">//Similar to First Prov</span></div>
<span style="font-family:monospace">}</span></div>
<span style="font-family:monospace"><br>
</span></div>
<div><span style="font-family:monospace">event_route[tm:branch-failure:DISPATCH_FIRST_PROV_FAILOVER]
{<br>
</span>
<div style="margin-left:40px"><span style="font-family:monospace">if (t_is_canceled()) exit;<br>
<br>
# next DST - only for 5xx or local timeout<br>
if ( t_check_status("5[[:digit:]]+") ||
(t_branch_timeout() && !t_branch_replied()) ) {<br>
</span></div>
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">if ( ds_next_dst() ) {<br>
</span></div>
</div>
<div style="margin-left:40px">
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">t_on_branch_failure("DISPATCH_FIRST_PROV_FAILOVER");<br>
route(RELAY);<br>
exit;<br>
</span></div>
</div>
</div>
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">} else {<br>
</span></div>
</div>
<div style="margin-left:40px">
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">xlog("L_ERR", "---
SCRIPT_DISPATCH_FIRST_PROV_FAILOVER: Failed to route
request to first prov.\n");<br>
</span></div>
</div>
</div>
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">}<br>
</span></div>
<span style="font-family:monospace">}<br>
</span></div>
<span style="font-family:monospace">}</span></div>
<div><span style="font-family:monospace"><br>
</span></div>
<div>
<div><span style="font-family:monospace">event_route[tm:branch-failure:DISPATCH_LAST_PROV_FAILOVER]
{</span></div>
</div>
<div>
<div style="margin-left:40px"><span style="font-family:monospace">//Similar to First Prov</span></div>
<span style="font-family:monospace">}</span></div>
<div><span style="font-family:monospace"><br>
</span></div>
<div><span style="font-family:monospace">branch_route[FIRST_PROV_BRANCH]
{<br>
</span>
<div style="margin-left:40px"><span style="font-family:monospace">uac_replace_to("$vn(some_var)");<br>
</span></div>
</div>
<div style="margin-left:40px"><span style="font-family:monospace">$ru = $vn(some_other_var);</span></div>
<div><span style="font-family:monospace">}</span></div>
<div><span style="font-family:monospace"><br>
</span></div>
<div><span style="font-family:monospace">branch_route[LAST_PROV_BRANCH]
{</span></div>
<div>
<div>
<div style="margin-left:40px"><span style="font-family:monospace">uac_replace_to("$vn(some_var)");<br>
</span></div>
</div>
<div style="margin-left:40px"><span style="font-family:monospace">$ru = $vn(some_other_var);</span><span style="font-family:monospace"></span></div>
<span style="font-family:monospace">}</span></div>
<div><span style="font-family:monospace"><br>
</span></div>
<div><span style="font-family:monospace">failure_route[PROVIDER_SERIAL]
{<br>
</span>
<div style="margin-left:40px"><span style="font-family:monospace">if (t_is_canceled()) exit;<br>
<br>
# next Provider - only for 5xx or local timeout<br>
if ( (t_check_status("5[[:digit:]]+") ||
(t_branch_timeout() && !t_branch_replied()))
&& is_avp_set("$avp(provider_order)") ) {<br>
</span></div>
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">xlog("L_NOTICE", "---
SCRIPT_PROVIDER_SERIAL: A failover provider was
selected: Forwarding to $avp(provider_order)\n");<br>
route(PROVIDER_SELECTION);<br>
route(RELAY);<br>
exit;<br>
</span></div>
</div>
<div style="margin-left:40px"><span style="font-family:monospace">} else if (
t_check_status("5[[:digit:]]+") || (t_branch_timeout()
&& !t_branch_replied()) ) {<br>
</span></div>
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">xlog("L_NOTICE", "---
SCRIPT_PROVIDER_SERIAL: No more provider options, giving
up\n");</span></div>
</div>
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">exit;<br>
</span></div>
</div>
<div style="margin-left:40px"><span style="font-family:monospace">} else {<br>
</span></div>
<div style="margin-left:40px">
<div style="margin-left:40px"><span style="font-family:monospace">xlog("L_NOTICE", "---
SCRIPT_PROVIDER_SERIAL: Non-5xx error received,
relaying\n");<br>
</span></div>
</div>
<div style="margin-left:40px"><span style="font-family:monospace">}<br>
</span></div>
<span style="font-family:monospace">}</span></div>
<div><span style="font-family:monospace"><br>
</span></div>
<div><span style="font-family:monospace">route[RELAY] {</span></div>
<div style="margin-left:40px"><span style="font-family:monospace">// Mostly identical to the
sample config file</span></div>
<span style="font-family:monospace">}<br>
</span>
<div>
<div><span style="font-family:monospace"><br>
</span></div>
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
</blockquote>
</div>
</div>
</div>
<br>
<fieldset></fieldset>
<pre>_______________________________________________
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</pre>
</blockquote>
<pre cols="72">--
Daniel-Constantin Mierla -- <a href="http://www.asipto.com" target="_blank">www.asipto.com</a>
<a href="http://www.twitter.com/miconda" target="_blank">www.twitter.com/miconda</a> -- <a href="http://www.linkedin.com/in/miconda" target="_blank">www.linkedin.com/in/miconda</a>
Kamailio Advanced Training - March 9-11, 2020, Berlin - <a href="http://www.asipto.com" target="_blank">www.asipto.com</a>
Kamailio World Conference - April 27-29, 2020, in Berlin -- <a href="http://www.kamailioworld.com" target="_blank">www.kamailioworld.com</a></pre>
</div>
</blockquote></div>