[asterisk-dev] [Code Review] 3377: ref count logs: Redo structure of log file, provide a python debugging tool

[Corey Farrell]

> On March 20, 2014, 5:12 a.m., Corey Farrell wrote:
> > We should remove utils/refcounter from all branches.  The format is changing, so the existing utils/refcounter will be unusable with 1.8.27.0 / 11.9.0 / 12.2.0.  I think providing utils/refcounter in those versions will only cause confusion.  Maybe we could enable installation of refcounter.py to ${ASTSBINDIR}/refcounter?
> 
> Matt Jordan wrote:
>     I disagree on removing refcounter, for the reasons Richard gave. Removing it is liable to result in more confusion, since its absence will be more noticeable than its presence.
>     
>     I'm not sure about installing refcounter.py by default. You would only run it when things have gone wrong and you need extra debugging. That feels like something that should be in the scripts folder, and not always available.

Actually I think Richard was saying to only keep it in cleanup, to ensure that the stale utils/refcounter is deleted.  I'm fine with not installing refcounter.py, but utils/refcounter will not work with the new ref_log format, so I think it should go away.


> On March 20, 2014, 5:12 a.m., Corey Farrell wrote:
> > /branches/1.8/main/astobj2.c, lines 228-233
> > <https://reviewboard.asterisk.org/r/3377/diff/2/?file=56243#file56243line228>
> >
> >     Can we deduplicate the ref_log writes into a macro?  I'm suggesting a macro so we can pass "%d" or "%s" for the format of the 'state' field, and let the compiler join the const strings.
> >     
> >     This would make it easier to append additional fields if desired, and ensure consistent output.  For example it is sometimes useful to add the current thread id to all ref_log messages.
> 
> Matt Jordan wrote:
>     I'm not sure how a macro is going to simplify this here. The state field in particular seems like it would necessitate at least two macros; at the end of the day, something has to provide a format string ("%d" or "%s"), and having two macros for three logging statements feels like overkill.


> On March 20, 2014, 5:12 a.m., Corey Farrell wrote:
> > /branches/1.8/main/astobj2.c, lines 1146-1152
> > <https://reviewboard.asterisk.org/r/3377/diff/2/?file=56243#file56243line1146>
> >
> >     What about ao2 objects created before astobj2_init?  I know that storing refs in astlogdir was my idea/request, but I'm concerned this will cause an unfixable issue with initialization order.  If we open the file too early, ast_config_AST_LOG_DIR will be the compiled value instead of the value in asterisk.conf.  If we open too late, startup messages are lost.  Further it's impossible to read astlogdir from asterisk.conf before __attribute__((constructor)).
> >     
> >     What if we allow an environmental variable to override /tmp/refs?  My goal with using astlogdir was to allow multiple instances of asterisk to run without causing conflicts in /tmp/refs.  This would be essential for the testsuite to check refs after tests.
> >     
> >     I don't think we can (safely) avoid opening/closing the refs file for every output.  Doing so would require us to open ref_log before any other __attribute__((constructor)) and closing it after all other __attribute__((destructor)), I think this would be impossible without starting to use constructor/destructor priorities.
> 
> Matt Jordan wrote:
>     If you create an ao2 object before astobj2_init, then you have broken the module load order. You should *not* ever create an ao2 object before that point.
>     
>     This may mean that astobj2_init has to move higher in the module load order. I've gone ahead and moved it up to being initialized immediately after reading the asterisk.conf file, as the CLI is initialized by that point as well. I'd rather not try to work around things that violate the order: if you try to access something in the core prior to it being initialized, that's an error.
>     
>     Note that astlogdir is read from asterisk.conf via read_config_maps. This happens immediately after printing out the intro message and registering the basic CLI functions. Again, if you create an ao2 object prior to reading asterisk.conf, you're violating the initialization order of the core and that's an error. Don't do that. :-)
>     
>     An environment variable that overrides the refs file is fine, but I'd consider that a separate feature from this patch.
>     
>     I don't think we need to open/close the refs file. That still feels like overkill, as fflush will write all data to disk. As astobj2 is initialized prior to any modules being loaded into memory, the ref_log file will be created before any constructor/destructor calls - which typically do not create ao2 objects as well (as they are used to set up module information).
>

What about AO2_GLOBAL_OBJ_STATIC?  I see now that it's not ao2_alloc'ed during __attribute__((constructor)), but it can be unref'ed during __attribute__((destructor)).  You're probably right about the initialization order.  Your initialization reorder should be good so long as config.c doesn't start using ao2, but I think my concern still applies to shutdown order.


- Corey


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On March 27, 2014, 5:08 p.m., Matt Jordan wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviewboard.asterisk.org/r/3377/
> -----------------------------------------------------------
> 
> (Updated March 27, 2014, 5:08 p.m.)
> 
> 
> Review request for Asterisk Developers, Corey Farrell and wdoekes.
> 
> 
> Repository: Asterisk
> 
> 
> Description
> -------
> 
> Note: while an improvement to Asterisk, this patch only affects Asterisk when compiled in -dev-mode. Since it has benefit only for developers looking to fix bugs, I'm proposing it for Asterisk 1.8+. The removal of refcounter should be done in trunk only.
> 
> Asterisk uses reference counted objects. A lot. As their use has spread, the bugs related to reference counting errors has grown as well. Central to resolving reference counting issues is the usage of REF_DEBUG; unfortunately, REF_DEBUG has had several problems:
> (1) It could not be enabled through menuselect
> (2) When not enabled globally, updates to objects were often lost, resulting in insufficient data to resolve problems
> (3) The format of the ref debug log file was not suitable for parsing
> 
> This patch changes REF_DEBUG in the following ways:
> (1) It makes REF_DEBUG a meneselect item when Asterisk is compiled with --enable-dev-mode
> (2) The ref debug log file is now created in the AST_LOG_DIR directory. Every run will now blow away the previous run (as large ref files sometimes caused issues). We now also no longer open/close the file on each write, instead relying on fflush to make sure data gets written to the file (in case the ao2 call being performed is about to cause a crash)
> (3) It goes with a comma delineated format for the ref debug file. This makes parsing much easier.
> (4) It throws out the refcounter utility and goes with a python script instead.
> 
> 
> Diffs
> -----
> 
>   /branches/1.8/utils/refcounter.c 410891 
>   /branches/1.8/utils/Makefile 410891 
>   /branches/1.8/main/astobj2.c 410891 
>   /branches/1.8/main/asterisk.c 410891 
>   /branches/1.8/include/asterisk/astobj2.h 410891 
>   /branches/1.8/contrib/scripts/refcounter.py PRE-CREATION 
>   /branches/1.8/channels/chan_sip.c 410891 
>   /branches/1.8/build_tools/cflags.xml 410891 
> 
> Diff: https://reviewboard.asterisk.org/r/3377/diff/
> 
> 
> Testing
> -------
> 
> Things spit out ref logs and the script parses them. Example below:
> 
> ==== Object 0x21ed9b8 history ====
> features.c[5427]:create_parkinglot 1  - [**constructor**]
> features.c[5707]:build_parkinglot +1  - [1]
> features.c[5392]:parkinglot_unref -1  - [2]
> features.c[6358]:build_dialplan_useage_map +1  - [1]
> features.c[6358]:build_dialplan_useage_map -1  - [2]
> features.c[4985]:find_parkinglot +1  - [1]
> features.c[5392]:parkinglot_unref -1  - [2]
> features.c[6358]:build_dialplan_useage_map +1  - [1]
> features.c[6358]:build_dialplan_useage_map -1  - [2]
> features.c[4955]:do_parking_thread +1  - [1]
> features.c[4957]:do_parking_thread -1  - [2]
> astobj2.c[955]:cd_cb_debug -1 deref object via container destroy - [1]
> astobj2.c[955]:cd_cb_debug -1 deref object via container destroy - [**call destructor**]
> 
> 
> Thanks,
> 
> Matt Jordan
> 
>

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