16 Dec
2008
16 Dec
'08
2:39 p.m.
On 16-12 10:52, Daniel-Constantin Mierla wrote:
On 12/16/08 10:15, Andrei Pelinescu-Onciul wrote:
It already is, the core contains the core selects and shared parts.
Jan.
On Dec 16, 2008 at 00:36, Daniel-Constantin
Mierla <miconda(a)gmail.com> wrote:
yes, indeed,
thanks!
Hello,
On 12/12/08 17:22, Jan Janak wrote:
x = f|t ("track" in ser avp terminology
y= r|u|d|g ("class")
g is a special case (it cannot be combined with f or t).
Here is the parse_avp_ident() usage comment:
/** parse an avp indentifier.
*
* Parses the following avp indentifier forms:
* - "i:<number>" - old form, deprecated (e.g. i:42)
* - "s:<string>" - old form, deprecated (e.g. s:foo)
* - "<track>.<name>" (e.g.: f.bar)
* - "<track>.<name>[<index>]" (e.g.:
f.bar[1])
* - "<track><class>.<name>" (e.g:
tu.bar)
* - "<track><class>.<name>[<index>]" (e.g:
fd.bar[2])
* - "<string>" (e.g.: foo)
* Where:
* <string> = ascii string
* <id> = ascii string w/o '[', ']', '.' and
'/'
* <name> = <id> | '/' regex '/'
* (Note: regex use is deprecated)
* <track> = 'f' | 't'
* (from or to)
* <class> = 'r' | 'u' | 'd' | 'g'
* (uri, user, domain or global)
* <index> = <number> | '-' <number> | ''
* (the avp index, if missing it means AVP_INDEX_ALL, but
* it's use is deprecated)
* More examples:
* "fr.bar[1]" - from track, uri class, avp "bar", the value
1.
* "tu./^foo/" - to track, user class, all avps for which the name
* starts with foo (note RE in avp names are deprecated).
* "t.did" - to track, "did" avp
*
* @param name - avp identifier
* @param *attr - the result will be stored here
* @return 0 on success, -1 on error
*/
On 12-12 00:25, Daniel-Constantin Mierla wrote:
> Hello,
>
> I think we need to decide about AVPs. Although not deeply
> investigated, ser seems to have couple of AVPs lists. In
> kamailio/openser it is one list.
>
> Can a ser developer describe a bit the AVP implementation as it
> is now there?
>
A long time ago we started using AVPs to store all kinds of configuration
information. We needed some sort of general configuration mechanism because
real-world scripts were getting too complex and at that time the AVPs were
readily available.
We started by loading attribute names and value from a database table into
AVPs. This mechanism was/is same as in k. We would always load a set of
attributes this way for a particular user (identified by username and domain
from his/her SIP URI). With this mechanism in place, we were able to load a
generic set of configuration options for a particular user of the server, I
guess you have the same.
To make the AVPs easily accessible from the configuration script, we added
support for AVP identifiers in the config script, so that you can access AVP
with name foo as $foo.
As we migrated more and more configuration options to AVPs, it became clear
that having just one set of AVPs was not enough. Although we could load all
the config options for the caller (From URI) from the database into a set of
AVPs, we could not do the same for the callee (Request-URI) at the same
time. We could not do it because they would conflict with the
AVPs of the caller as both users could have AVPs with same names
but different values.
To get around this issue we added another list of AVPs. The new AVP list
works the same way, it can contain AVPs with same names as AVPs in the
original list and they do not conflict. All functions that work with lists
of AVPs now take the list to work on as parameter.
To make both AVP lists available in the configuration script, we extended
the syntax of AVPs identifiers so the script write can choose the AVP list
to work with. SO instead of just $foo you can write either
$f.foo or $t.foo
$f refers to the original AVP list which is commonly associated with the
caller. The address/uid of the caller is taken from From header, hence the
'f' in the identifier. $t refers to the AVP list which contains
configuration settings of the callee. The address/uid of the calle can be
taken either from the Request-URI or To headers, hence the 't' in the
identifier.
The original syntax without any list identifier is still available, in other
words you can still write $foo, this is defined as a shorthand for
$f.foo. If you do not specify the AVP list to be used then you are referring
to the list containing AVPs of the caller (From).
It also turned out that in some cases we would be having too many attributes
in the database table storing AVPs. This can happen in bigger setups, having
tens or hundreds of thousands users or serving multiple domains. This can
slow the database down and makes SER load too much data. Based on my
observations it is common that a large number of users have AVPs with same
values. If ten thousands of users have attribute named 'foo' with value
'bar' then the attribute will be stored in the database ten thousand times.
As a remedy for this problem, we introduced the concept of AVP levels. The
AVPs described so far and stored in user_attrs table are called user-level
attributes and they store configuration specific to particular users. Then
we added another two AVP lists to store so called domain-level AVPs.
Domain-level AVPs are used to store configuration information that is shared
by a group of users. Domain-level AVPs are stored in a separate database
table, the name of the table is domain_attrs and its contents is cached in
memory by 'domain' SER module. This is an important difference, while
user-level AVPs need to be loaded every time a SIP request is processed,
domain-level AVPs are only loaded when the contents of domain_attrs table
has changed.
The domain-level AVPs are called 'domain' because they are tied to a
particular domain handled by the SIP server. That could be 'iptel.org',
'sip-router.org', and so on. This mainly useful for multi-domain
setups. There are two domain-level AVP lists because it is common that SER
works with two domains at the same time, the domain from From header
(caller's domain) and the domain from Request-URI or To (callee's domain).
Again, we extended the syntax of AVP identifiers in the configuration
file. So you can write:
$fu.foo -- this way you are asking for the value of the user-level foo AVP.
$fd.foo -- This will return the value of the domain-level foo AVP.
And similarly there is $tu and $td for callee's user-level and domain-level
AVPs. If you specify 'u' in the AVP identifiers then SER searches only the
list of user-level attributes. If you specify 'd' then SER searches only the
list of domain-level attributes.
This behavior changes if you do NOT specify the level to be searched. In
that case SER searches the user-level list first and if no match is found
then the domain-level list will be searched. Thus if you write:
$f.foo
then you are telling SER to search for the value of 'foo' AVP in the
user-level list and continue with the domain-level list if no match is
found. In other words, user-level AVPs have higher priority than
domain-level AVPs. With this system you can efficiently set a configuration
option for all users within a domain by creating a domain-level attribute
and yet you can override that option with user-level attributes for
particular users within that domain.
Then there are the global AVPs. Global AVPs can be used to store settings
applicable to the whole SIP server and all domains on that server. Global
AVPs are stored in global_attrs table and the contents of that table is
cached in memory by gflags module. There is only one list of global
AVPs. Global AVPs can be accessed with:
$g.foo
(note that there is no 'f' or 't' in the identifier). The list of
global
AVPs is searched after the list of domain-level AVPs. So if you write:
$f.foo
Then SER searches user-level AVPs first, then domain-level and then the
global AVPs.
And finally there are also so called URI-level AVPs. They work just
like user-level AVPs, but a single user can have multiple sets of
uri-level AVPs. They are tied to SIP URIs of that user. Uri-level AVPs are
denoted by 'r' in the AVP identifier, for example:
$fr.foo
so, if I understood correctly, there are couple of combinations
between the dot, with one or two letters, right?
Like:
$xy.name
where x = f|t|g and y may be missing or u|d|r
Then we can get rid of overlapping in the
namespace if we enforce
usage of $f.foo for $foo . In K there are couple of PV that use dot
in classname (a PV can be $classname or $classname(innername)), but
they are proposed to be removed.
For the time being in sip-router this is handled in the following way:
$(...) -> pvar
$foo(...) -> pvar
$foo[...] -> avp
$bar.foo -> avp (if it has a dot in it -> avp)
$foo (no dot, [] or ()) -> try first to resolve it as pvar and if it
fails consider it an avp.
For the current version I think this is the most compatible way. I'll
use the same approach for ser module fixups (so all ser module that use
core fixup functions will be able to use also pvars).
One could also force kamailio or ser behaviour, by starting the
script with #!KAMAILIO or #!SER.
For future versions we should rethink how everything is accessed.
For example I would use $foo for script variables and some other form
for avps or the current pvar $foo. Also we would have to unify selects
with the select like part of the pvars.
(Note for ser users: pvars in kamailio are used to access script vars,
avps, message headers and something which is kind of similar to ser
selects.).
Perhaps select implementations can be moved in modules, as well.
Integration has to be done at some point anyhow.