21 Feb
2018
21 Feb
'18
12:33 p.m.
Hello,
(cross-posting being something I want to get developers and users
express their opinions).
We were recently in a (lucky) situation to have two new modules
submissions targeting more or less the same purpose: allowing to use
Kamailio with a Redis backend via database API.
One was submitted by Andreas Granig (Sipwise) and already merged with
the name db_redis, because it was designed from the beginning as a
generic DB connector, so the module can be used with auth_db, acc,
usrloc, ...
* https://www.kamailio.org/docs/modules/devel/modules/db_redis.html
The second one was submitted by Surendra Tiwari (Plivo), initially
having a naming conflict with db_redis, but renamed to db_redisusrloc,
see the pull request at:
* https://github.com/kamailio/kamailio/pull/1446
Now, this email is about deciding the way to go forward with the second
module.
It was designed to be used only for usrloc in the first phase, with many
specific usrloc attributes hard coded inside db_redisusrloc. Surendra
said (in a private chat) that the long term plan is to make it work for
other modules. Anyhow, at this moment is very tied to usrloc, therefore
the name of the module.
Given that the backend (Redis) is not an SQL engine, mapping over
Kamailio's DB API needs some schema definition (see the readme of
db_redis) in order to make it generic and work for all our modules that
use a DB backend.
On the other hand, to squeeze the best of the backend, specially in
no-SQL cases, having a dedicated DB connector module optimized for a
specific module might help to get more
performances/high-availability/scalability from the backend itself.
In this case, for example the expires value for a contact record can be
set inside redis, so kamailio module doesn't have to run a timer routine
to clean up (it doesn't mean db_redisusrloc does it right now, I didn't
have time for a proper review, just giving an example). Surendra said
they use it in production for couple of months now and it is several
times faster than using usrloc with db_postgres (iirc, not db_mysql) for
db_mode=3 (database only mode).
But of course, the reverse of the medal with a dedicated db connector
for a module: it adds overhead to code maintenance (besides generic
updates due to external library changes, I expect changing something
relevant in usrloc, like adding new columns, would require updates in
this module as well).
So, there are few things I want feedback on:
1) how do you fill about splitting from a generic-only DB connectors to
have also some dedicated ones? This is more from confusion point of
view, as a general rule so far, we do not deny contributions if there
are other options for same kind of feature (e.g., many lcr or nat
traversal options). As long as the contributor is willing to maintain
the code, we were fine.
2) I guess usrloc, presence and dialog modules would be the main
suspects that would benefit for such dedicated connectors, in other
cases might not worth adding dedicated connectors. Missing any other
module one would like to squeeze more performances with a dedicated
connector?
3) should we set a different naming policy for such modules, for
example: use *dbs_* prefix instead *db_*, to suggest better it is a
DataBase Specific connector?
4) Andreas said he plans to do some performance testing of usrloc module
with the two modules and see the differences. Anyone else that wants to
do it? It can be a good metric to see if it worth going one way or another?
5) Helping to review the pull request, specially if you use Redis, is
appreciated. Personally I am very short in available time these days,
next week I plan do to new Kamailio stable releases, so the schedule is
not getting lighter in my side.
Cheers,
Daniel
--
Daniel-Constantin Mierla
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Kamailio Advanced Training - March 5-7, 2018, Berlin - www.asipto.com
Kamailio World Conference - May 14-16, 2018 - www.kamailioworld.com
21 Feb
21 Feb
12:48 p.m.
New subject: [SR-Users] RFC: db_redisusrloc module - review and how to deal with
Hi,
I have not dived into the technical specifics deeply or examined the
innards of db_redis, so this is really shooting from the hip:
I can appreciate the very legitimate dilemma here. However, in general I
would advocate for keeping all DB connectors generic.
Although I understand that there are some punishing generalisations and
contortions required to shoehorn particular modules' schematic
requirements into the more general DB API, there is a lot of value in
the highly consistent database agnosticism afforded by doing this. This
is similar to the trade-offs involved in using ORMs a lot of the time.
As things currently stand, it is possible to use any db_* backend with
Kamailio in a highly interchangeable way, and not many DB-backed systems
can truly deliver on that promise. Kamailio shines as a rare exception.
The other problem is that the leaky / inconsistent abstractions involved
in more Byzantine DB module choices will be confusing to users, most of
whom are not software engineers presumably and will not easily
understand the difference between a module-specific DB connector and a
generic one. It will also lead to some needless duplication of effort
and possibly lopsided support for one or the other pathway to the
database in cases where a module has both generic and module-specific
connector support.
Finally, although I understand that third parties contributing modules
are charged with maintaining them, it seems to be a practical effect
that you (Daniel) and others are dragged into maintaining orphaned or
semi-orphaned modules, or the "plumbing" dependencies that they generate
within common code. The project already has a bewildering array of
modules, all moving at different speeds, having different levels of
sophistication and so forth. Now, I know that I have always taken a more
conservative position on matters of curation of third-party
contributions relative to the implicit maintenance burden, and we may
differ on that, but I think pouring more fuel on that fire by splicing
in multiple levels of DB abstraction for some modules will create
unnecessary maintenance headaches without the corresponding pay-off.
Whether the database is traditional relational or schemaless, I don't
think it's unreasonable to ask that any DB-backed module adhere to the
common DB API and use those mechanisms to interact with the DB. It just
leads to more consistent, maintainable code and more predictable
outcomes, while providing a level of flexibility people have come to
expect with the RDBM-backed modules.
-- Alex
--
Alex Balashov | Principal | Evariste Systems LLC
Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
1:03 p.m.
New subject: [SR-Users] RFC: db_redisusrloc module - review and how to deal with
Hello,
for fairness and a more complete picture, I should have mentioned that I
am somehow the first that broke into module specific backend with topos
and topos_redis. In that case, I was also guided by the goals of
squeezing what ever can be exploited in terms of performances from Redis
backend, given that topology hiding with stripping/adding back headers
for all SIP traffic needs be be (ideally) very fast.
The topos module had DB API support and can be used with mysql,
postgres, etc ... topos_redis was added as an alternative to use
directly a Redis server. However, topis_redis is not on top of DB API,
therefore a name not related to it at all.
Cheers,
Daniel
On 21.02.18 10:48, Alex Balashov wrote:
Hi,
I have not dived into the technical specifics deeply or examined the
innards of db_redis, so this is really shooting from the hip:
I can appreciate the very legitimate dilemma here. However, in general I
would advocate for keeping all DB connectors generic.
Although I understand that there are some punishing generalisations and
contortions required to shoehorn particular modules' schematic
requirements into the more general DB API, there is a lot of value in
the highly consistent database agnosticism afforded by doing this. This
is similar to the trade-offs involved in using ORMs a lot of the time.
As things currently stand, it is possible to use any db_* backend with
Kamailio in a highly interchangeable way, and not many DB-backed systems
can truly deliver on that promise. Kamailio shines as a rare exception.
The other problem is that the leaky / inconsistent abstractions involved
in more Byzantine DB module choices will be confusing to users, most of
whom are not software engineers presumably and will not easily
understand the difference between a module-specific DB connector and a
generic one. It will also lead to some needless duplication of effort
and possibly lopsided support for one or the other pathway to the
database in cases where a module has both generic and module-specific
connector support.
Finally, although I understand that third parties contributing modules
are charged with maintaining them, it seems to be a practical effect
that you (Daniel) and others are dragged into maintaining orphaned or
semi-orphaned modules, or the "plumbing" dependencies that they generate
within common code. The project already has a bewildering array of
modules, all moving at different speeds, having different levels of
sophistication and so forth. Now, I know that I have always taken a more
conservative position on matters of curation of third-party
contributions relative to the implicit maintenance burden, and we may
differ on that, but I think pouring more fuel on that fire by splicing
in multiple levels of DB abstraction for some modules will create
unnecessary maintenance headaches without the corresponding pay-off.
Whether the database is traditional relational or schemaless, I don't
think it's unreasonable to ask that any DB-backed module adhere to the
common DB API and use those mechanisms to interact with the DB. It just
leads to more consistent, maintainable code and more predictable
outcomes, while providing a level of flexibility people have come to
expect with the RDBM-backed modules.
-- Alex
--
Daniel-Constantin Mierla
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Kamailio Advanced Training - March 5-7, 2018, Berlin - www.asipto.com
Kamailio World Conference - May 14-16, 2018 - www.kamailioworld.com
22 Feb
22 Feb
1:42 a.m.
New subject: RFC: db_redisusrloc module - review and how to deal with
Am Mittwoch, 21. Februar 2018, 10:33:23 CET schrieb Daniel-Constantin Mierla:
[..]
We were recently in a (lucky) situation to have two new modules
submissions targeting more or less the same purpose: allowing to use
Kamailio with a Redis backend via database API.
[..]
So, there are few things I want feedback on:
1) how do you fill about splitting from a generic-only DB connectors to
have also some dedicated ones? This is more from confusion point of
view, as a general rule so far, we do not deny contributions if there
are other options for same kind of feature (e.g., many lcr or nat
traversal options). As long as the contributor is willing to maintain
the code, we were fine.
2) I guess usrloc, presence and dialog modules would be the main
suspects that would benefit for such dedicated connectors, in other
cases might not worth adding dedicated connectors. Missing any other
module one would like to squeeze more performances with a dedicated
connector?
Hello,
I also think that the possibility to use a generic DB connection module to
interact with several databases from different modules is really beneficial in
Kamailio and we should keep this possibility.
Even if there is a small performance penalty in using a more generic module I
still think the benefits in maintenance over the long term are in favor of
only one generic redis module (as in this example). In the end processors are
still getting faster/getting more cores every year. Our maintenance and
reviewing capacity especially for core and plumping parts stays more or less
the same.
If there are bigger performance differences (like an order of magnitude)
between the two modules then the reason is probably some implementation issues
in the code. In this case they should be simply fixed in the generic module.
Best regards,
Henning
3) should we set a different naming policy for such
modules, for
example: use *dbs_* prefix instead *db_*, to suggest better it is a
DataBase Specific connector?
4) Andreas said he plans to do some performance testing of usrloc module
with the two modules and see the differences. Anyone else that wants to
do it? It can be a good metric to see if it worth going one way or another?
5) Helping to review the pull request, specially if you use Redis, is
appreciated. Personally I am very short in available time these days,
next week I plan do to new Kamailio stable releases, so the schedule is
not getting lighter in my side.
Cheers,
Daniel
3:06 a.m.
New subject: [SR-Users] RFC: db_redisusrloc module - review and how to deal with
Opinion of a Kamailio novice, take with a grain of salt:
Would it be appropriate to think about this general problem more akin to
how some modules support either a file or a db backend? Imagine this world:
- To be called a DB in Kamailio parlance, a backend needs to conform to
the DB API, be generically usable, etc – all the good stuff we have now.
- Some module (foo) has 3 modes of operation:
- file – the module uses a file on disk
- db – the module uses the DB api
- redis – a very foo-specialized application of Redis and its features
In my mind, having a specialized Redis backend for a module is no different
than having a file backend in addition to a DB backend (see the dispatcher
module for example).
Just because something (redis) is database-like, doesn't necessarily mean
that it can/should only be accessed as a DB (above definition), especially
if the tool supports features that shouldn't be in the DB API, and those
features are very valuable to a specific module.
This would imply that there is a db_redis module which allows Redis to
participate in anything demanding a DB (as defined above), as well as a
foo_redis (name not important) module, which leverages Redis in a very
foo-specific way.
It would of course be the responsibility of module owners to decide when it
is truly appropriate to have this sort of specialized support, or when the
DB api is sufficient (including the potential additional maintenance
burden, attractiveness to clients, etc).
On Wed, Feb 21, 2018 at 1:35 AM Daniel-Constantin Mierla <miconda(a)gmail.com>
wrote:
Hello,
(cross-posting being something I want to get developers and users
express their opinions).
We were recently in a (lucky) situation to have two new modules
submissions targeting more or less the same purpose: allowing to use
Kamailio with a Redis backend via database API.
One was submitted by Andreas Granig (Sipwise) and already merged with
the name db_redis, because it was designed from the beginning as a
generic DB connector, so the module can be used with auth_db, acc,
usrloc, ...
* https://www.kamailio.org/docs/modules/devel/modules/db_redis.html
The second one was submitted by Surendra Tiwari (Plivo), initially
having a naming conflict with db_redis, but renamed to db_redisusrloc,
see the pull request at:
* https://github.com/kamailio/kamailio/pull/1446
Now, this email is about deciding the way to go forward with the second
module.
It was designed to be used only for usrloc in the first phase, with many
specific usrloc attributes hard coded inside db_redisusrloc. Surendra
said (in a private chat) that the long term plan is to make it work for
other modules. Anyhow, at this moment is very tied to usrloc, therefore
the name of the module.
Given that the backend (Redis) is not an SQL engine, mapping over
Kamailio's DB API needs some schema definition (see the readme of
db_redis) in order to make it generic and work for all our modules that
use a DB backend.
On the other hand, to squeeze the best of the backend, specially in
no-SQL cases, having a dedicated DB connector module optimized for a
specific module might help to get more
performances/high-availability/scalability from the backend itself.
In this case, for example the expires value for a contact record can be
set inside redis, so kamailio module doesn't have to run a timer routine
to clean up (it doesn't mean db_redisusrloc does it right now, I didn't
have time for a proper review, just giving an example). Surendra said
they use it in production for couple of months now and it is several
times faster than using usrloc with db_postgres (iirc, not db_mysql) for
db_mode=3 (database only mode).
But of course, the reverse of the medal with a dedicated db connector
for a module: it adds overhead to code maintenance (besides generic
updates due to external library changes, I expect changing something
relevant in usrloc, like adding new columns, would require updates in
this module as well).
So, there are few things I want feedback on:
1) how do you fill about splitting from a generic-only DB connectors to
have also some dedicated ones? This is more from confusion point of
view, as a general rule so far, we do not deny contributions if there
are other options for same kind of feature (e.g., many lcr or nat
traversal options). As long as the contributor is willing to maintain
the code, we were fine.
2) I guess usrloc, presence and dialog modules would be the main
suspects that would benefit for such dedicated connectors, in other
cases might not worth adding dedicated connectors. Missing any other
module one would like to squeeze more performances with a dedicated
connector?
3) should we set a different naming policy for such modules, for
example: use *dbs_* prefix instead *db_*, to suggest better it is a
DataBase Specific connector?
4) Andreas said he plans to do some performance testing of usrloc module
with the two modules and see the differences. Anyone else that wants to
do it? It can be a good metric to see if it worth going one way or another?
5) Helping to review the pull request, specially if you use Redis, is
appreciated. Personally I am very short in available time these days,
next week I plan do to new Kamailio stable releases, so the schedule is
not getting lighter in my side.
Cheers,
Daniel
--
Daniel-Constantin Mierla
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Kamailio Advanced Training - March 5-7, 2018, Berlin - www.asipto.com
Kamailio World Conference - May 14-16, 2018 - www.kamailioworld.com
_______________________________________________
Kamailio (SER) - Users Mailing List
sr-users(a)lists.kamailio.org
https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
23 Feb
23 Feb
4:45 p.m.
New subject: [SR-Users] RFC: db_redisusrloc module - review and how to deal with
Hi, just sharing my experience from last year while adding some features to
db_postgres and db_sqlite
On Wed, Feb 21, 2018 at 1:33 AM, Daniel-Constantin Mierla <miconda(a)gmail.com
wrote:
Hello,
(cross-posting being something I want to get developers and users
express their opinions).
We were recently in a (lucky) situation to have two new modules
submissions targeting more or less the same purpose: allowing to use
Kamailio with a Redis backend via database API.
One was submitted by Andreas Granig (Sipwise) and already merged with
the name db_redis, because it was designed from the beginning as a
generic DB connector, so the module can be used with auth_db, acc,
usrloc, ...
* https://www.kamailio.org/docs/modules/devel/modules/db_redis.html
The second one was submitted by Surendra Tiwari (Plivo), initially
having a naming conflict with db_redis, but renamed to db_redisusrloc,
see the pull request at:
* https://github.com/kamailio/kamailio/pull/1446
Now, this email is about deciding the way to go forward with the second
module.
It was designed to be used only for usrloc in the first phase, with many
specific usrloc attributes hard coded inside db_redisusrloc. Surendra
said (in a private chat) that the long term plan is to make it work for
other modules. Anyhow, at this moment is very tied to usrloc, therefore
the name of the module.
Given that the backend (Redis) is not an SQL engine, mapping over
Kamailio's DB API needs some schema definition (see the readme of
db_redis) in order to make it generic and work for all our modules that
use a DB backend.
On the other hand, to squeeze the best of the backend, specially in
no-SQL cases, having a dedicated DB connector module optimized for a
specific module might help to get more
performances/high-availability/scalability from the backend itself.
In this case, for example the expires value for a contact record can be
set inside redis, so kamailio module doesn't have to run a timer routine
to clean up (it doesn't mean db_redisusrloc does it right now, I didn't
have time for a proper review, just giving an example). Surendra said
they use it in production for couple of months now and it is several
times faster than using usrloc with db_postgres (iirc, not db_mysql) for
db_mode=3 (database only mode).
But of course, the reverse of the medal with a dedicated db connector
for a module: it adds overhead to code maintenance (besides generic
updates due to external library changes, I expect changing something
relevant in usrloc, like adding new columns, would require updates in
this module as well).
So, there are few things I want feedback on:
1) how do you fill about splitting from a generic-only DB connectors to
have also some dedicated ones? This is more from confusion point of
view, as a general rule so far, we do not deny contributions if there
are other options for same kind of feature (e.g., many lcr or nat
traversal options). As long as the contributor is willing to maintain
the code, we were fine.
Generic is adding a lot of value in reusability but dedicated ones may also
be needed, especialy with NoSQL.
Even with SQL DB abstraction we are sometimes facing limitations.
Since the db abstraction is generic it may prevent the use of some back-end
specific features, even with real SQL back-end when something is *statement
specific*, one example :
when adding the postgres upsert last year, introduced in Postgres 9.5 the
postgres team decided that the conflict/constraints must be specified
explicitely in the statement, in this case I decided to do automatic
constraint detections so that db_postgres could automaticaly always do
upsert when insert_update is used, this was working fine with mysql
because insert for update is generic.
In such case may still have several options like extendeding the DB
abstraction or bypassing it by presseting specific values/decisions in the
db_x module (per connection, table, statement type) but if it is per
statement I beleive the only option is to extend the db abstraction.
2) I guess usrloc, presence and dialog modules would be the main
suspects that would benefit for such dedicated connectors, in other
cases might not worth adding dedicated connectors. Missing any other
module one would like to squeeze more performances with a dedicated
connector?
I agree, dedicated ones may be valuable, Kamailio is able to do many
things but it seems valuable to also be specialised in doing some tasks
extremely well.
3) should we set a different naming policy for such
modules, for
example: use *dbs_* prefix instead *db_*, to suggest better it is a
DataBase Specific connector?
4) Andreas said he plans to do some performance testing of usrloc module
with the two modules and see the differences. Anyone else that wants to
do it? It can be a good metric to see if it worth going one way or another?
5) Helping to review the pull request, specially if you use Redis, is
appreciated. Personally I am very short in available time these days,
next week I plan do to new Kamailio stable releases, so the schedule is
not getting lighter in my side.
Cheers,
Daniel
--
Daniel-Constantin Mierla
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Kamailio Advanced Training - March 5-7, 2018, Berlin - www.asipto.com
Kamailio World Conference - May 14-16, 2018 - www.kamailioworld.com
_______________________________________________
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2407
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2409
days old
5 comments
5 participants
participants (5)
-
Alex Balashov -
Daniel-Constantin Mierla -
Henning Westerholt -
Josh Converse -
Julien Chavanton