[OpenSIPS-Devel] presence non-unique totag and more
Kennard_White at logitech.com
Kennard_White at logitech.com
Wed Oct 27 07:26:31 CEST 2010
Hi Anca,
Did you have a chance to speak with Bodgan about to to-tag generation? Just
wondering which direction you are going in.
Thanks,
Kennard
From: Anca Vamanu <anca at opensips.org>
To: devel at lists.opensips.org
Date: 09/29/2010 01:55 AM
Subject: Re: [OpenSIPS-Devel] presence non-unique totag and more
Sent by: devel-bounces at lists.opensips.org
Hi Kennard,
I agree, the best solution is to generate a unique to tag in the presence
module - it is easy to do in tm module ( the b2b_entities module already
does this, it uses t_reply_with_body function), but in sl there is no
support to inject the to tag. I will speak with Bogdan to see what solution
we can find for this.
On 09/28/2010 09:47 PM, Kennard_White at logitech.com wrote:
Hi Anca,
There are some "big" issues that I don't think I can solve. I'll try
to describe:
1. Need to decide if indexing is based upon totag (if globally
unique) or the 5-tuple of from_uri,from_tag,to_uri,to_tag,callid.
Whichever is decided, should be used informally for hash & db, for
all ops (insert, search and delete). Current code has mixture. My own
"vote" is to make totag unique (within the sever), much the way
PUBLISH's etag is unique. Then a subscription can be identified by a
single key (the totag).
2. The unique totag needs to be generated *before* sending the
response. E.g., all the hash&db operations need to complete
successfully before sending reply message. With current code where
the totag is generated as side-effect of sending 2XX, the client
thinks it has a good subscription when in fact it has failed due to
DB issue.
3. Consequence of above, my suggestion is generate totag within
presence module, complete DB ops, then send 2XX. Need new API so that
the totag can be passed into tm layer, instead of tm layer
generating. This is bigger change than I want to do (and even if I
did, don't know if patch would be accepted).
4. The totag generated by tm has a very long prefix that is GUID for
the opensips instance, and there is comment in code about this being
used to detect spirals. Is this used? If not, perhaps consider
dropping this prefix portion and making the dialog-specific portion
longer (and unique).
5. I don't understand why the totag is generated the way it is. The
method used makes sense for the sl module: the to tag (because hash
of prior hop state) will be the same for replies generated for
retransmits. But why do this in tm module? The whole "point" of tm is
that it keeps state to handle retransmits. And the whole "point" of
the totag is to provide a convenient handle to look up dialog state.
Clearly, I'm missing something here.
6. I only use the "presence_xml" module. The other presence modules
(e.g., pua) use the low-level APIs of the presence module. I'm just
not familiar with how these other modules work, and cannot assess
impact of changes to core presence module.
There is no other module to generate a to tag - only presence module does
this.
7. The startup order is messy. Currently the db-restore is done from
mod_init(). This has two problems: (a) the other modules may or may
not have been initialized, which leads to non-determinism in how the
get_auth_status() is handled, and (b) the statistics variables are
not ready. Suggest moving db-restore into the "first" child_init,
assuming stats are ready then. But really need a thread-join for all
the child-inits prior to handling traffic. E.g., need to block all
PUB/SUB traffic until restore is complete. (Ideally generating 5XX
with retry-after header). Don't really know how to implement this
join/blocking.
Indeed, get_auth_status might not be available in mod_init if the modules
that add events are not loaded before. We can move the reload from db in
the first child as you suggested.
I will let you know when I finish the unique to tag implementation.
Thanks and regards,
--
Anca Vamanu
www.voice-system.ro
As a consequence of all the above, I don't think I can ever give you
a final patch, or even any much better than what you have now. I just
didn't want you to think my patch was good or ready for production.
Need to resolve above big issues. If you decide to go with a global
totag, then some of my changes will need to be backed out. I'll
happily deal with any version control conflicts if it gets us closer
to final solution.
Kennard
Inactive hide details for "SourceForge.net" ---09/28/2010 02:30:29
AM---Patches item #3076805, was opened at 2010-09-28 00:00 M
"SourceForge.net" ---09/28/2010 02:30:29 AM---Patches item #3076805,
was opened at 2010-09-28 00:00 Message generated for change (Comment
added) m
From: "SourceForge.net" <noreply at sourceforge.net>
To: noreply at sourceforge.net
Date: 09/28/2010 02:30 AM
Subject: [OpenSIPS-Devel] [ opensips-Patches-3076805 ] presence
non-unique totag and more
Sent by: devel-bounces at lists.opensips.org
Patches item #3076805, was opened at 2010-09-28 00:00
Message generated for change (Comment added) made by anca_vamanu
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=1086412&aid=3076805&group_id=232389
Please note that this message will contain a full copy of the comment
thread,
including the initial issue submission, for this request,
not just the latest update.
Category: modules
Group: trunk
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Kennard White (kennardwhite)
>Assigned to: Anca Vamanu (anca_vamanu)
Summary: presence non-unique totag and more
Initial Comment:
Attached is a bundle of changes to presence module. We deployed
opensips1.6 and saw a number of different failures under production
load. This patch isn't finished quality: it is just snapshot of where
I stand now. I thought it worth sharing the issues I've seen so far.
A clean solutions really require larger change outside the scope of
just the presence module. I'll send email to the list about these
ideas.
This includes:
* Partial bug fix for non-unique totags. The hash-table and DB code
for deleting subscriptions assumes that the totag is unique. But the
totag has only 16 bits of possible uniqueness per server (it is CRC
of branch info). IN practice, easy to get totag collisions after few
thousand subscribers. Patch includes fix to the hash-table side but
the DB side is still broken. For now, code just does nothing to DB
when deleteting a subscription, and just lets it expire out.
* Bug fix for expiring subscriptions from DB prior to updating.
Subscriptions that we renewd (via reSUB) are deleted from DB prior to
writing the new (unexpired) time into the DB. Change to do DB delete
after sync.
* Bug fix for "if ( foo & NO_UPDATE_DB) when NO_UPDATE_DB is zero
value. Note that at least one other module has same bug and is not
patched here.
* Addition of statistics for presence module. The isn't cleanest of
implementations because the DB restore function runs before
statistics are available. Would be much cleaner if DB restore could
run after stats are available.
* Addition of new 'activeSubs' mi command to help trace down these
problems.
* More info in many of the log messages to help trace down these
errors.
* Addition of 'override_481_code' as work-around for bad resiprocate
clients. We use this option to force a 5xx code instead of standard
481 since some versions of resip get stuck with 481.
* Change to NOTIFY code to node register a response callback function
if subscription is being terminated. No point is looking for 481
response if sub is terminated.
* Fix for expires_offset as discussed previously to prevent
subscriptions walking to zero length.
----------------------------------------------------------------------
>Comment By: Anca Vamanu (anca_vamanu)
Date: 2010-09-28 12:30
Message:
Hi Kennard,
Thank you for this complex patch - some issues are really bugs that
we
were not aware of and the additions seem useful. I will review this
patch
and send comments if I have any. I will not apply it until you say
it's the
final version.
Regards,
Anca
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=1086412&aid=3076805&group_id=232389
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