Re: keepalived.data and keepalived.stats json output

Hello,

I have made some progress on the matter. I did not know much about POSIX 
signals a few days ago, so I spent a lot of time figuring out how to 
manipulate them.

To keep the code explicit, I defined two constants SIGDATAJS and 
SIGSTATJS. They are currently defined this way:

--- configure.ac  2017-02-18 12:52:10.000000000 +0100
+++ configure.ac  2017-07-17 21:07:37.994953146 +0200
@@ -46,6 +46,8 @@
    [
  #ifndef _CONFIG_H
  #define _CONFIG_H
+#define SIGDATAJS ( __SIGRTMIN + 4 )
+#define SIGSTATJS ( __SIGRTMIN + 5 )
    ])
  AH_BOTTOM(
    [


__SIGRTMIN to ( __SIGRTMIN + 3 ) are reserved on Linux so I started at +4.

The file configure.ac being really long, I am not yet sure this is the 
best place to define those constants. It looks like I need them in 
config.h for the code to compile.

Can you confirm this is a clean place to define those constants ?

Meanwhile, I am starting to work on the functions that will actually 
write the json output (so far they create files and write one static 
string in it).

Regards,


On 14/07/17 01:28 PM, Damien Clabaut wrote:
>
> Hello Quentin and thank you for your answer.
>
> I believe we will add two extra signals (USR3 and USR4, or something 
> else) and use them to write output to /tmp/keepalived_data.json and 
> /tmp/keepalived_stats.json.
>
> This way users can keep using existing scripts with existing 
> behaviour, and develop future scripts on new behaviour, at the same time.
>
> Regards,
>
>
> On 14/07/17 09:47 AM, Quentin Armitage wrote:
>> On Fri, 2017-07-14 at 08:35 -0400, Damien Clabaut wrote:
>>> Hello Keepalived developers,
>>>
>>> My team and I are considering modifying the file
>>> https://github.com/acassen/keepalived/blob/master/keepalived/vrrp/vrrp_print.c  
>>> in order to make the /tmp/keepalived.data and /tmp/keepalived.stats a
>>> valid json.
>>>
>>> In your opinion, what would be the best way to do this ?
>>>
>>> - Patching current functions so that kill -USR1 and kill -USR2 return
>>> valid json ?
>>>
>>> - Adding handlers for kill -USR3 and kill -USR4 to return valid json,
>>> leaving -USR1 and -USR2 in their current states ?
>>>
>>> The idea would be to port this patch to the master branch in the end.
>>>
>>> Regards,
>>>
>> I don't think we can alter the current functionality - there might be 
>> users who have scripts that parse the output files.
>>
>> Of course, there are no signals USR3 and USR4, but there is no reason 
>> why you can't use other signals that aren't currently used.
>>
>> I can see three ways of doing this, each of which I would be happy with:
>> 1. Use 2 new signals (this seems to offer the greatest flexibility)
>> 2. Have a global configuration option, e.g. dump_json, which if set 
>> will make USR1 and USR2 write json output
>> 3. Use 1 additional signal that each time it is invoked toggles 
>> between the current format and json (the default would need to be the 
>> current format); this probably isn't the best approach.
>>
>> Depending on how much overhead in terms of code size there is with 
>> the json output, it might be useful to make the inclusion of json 
>> output a compile time option enabled by a configure option --enable-json.
>>
>> It would be good not to duplicate the existing code, since at the 
>> moment when a new option is added we already have to update 
>> vrrp_print.c, vrrp_data.c and vrrp_snmp.c, and to have to update a 
>> fourth place in the code would be somewhat excessive. In fact I have 
>> in mind that at sometime the code in vrrp_print.c and the dump_vrrp() 
>> code in vrrp_data.c should be merged.
>>
>> I hope that helps,
>>
>> Quentin Armitage
>>
>>
>
> -- 
> Damien Clabaut
> R&D vRouter
> ovh.qc.ca
>
>
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-- 
Damien Clabaut
R&D vRouter
ovh.qc.ca

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