Prefetch Serve expired behavior per cache

[George Thessalonikefs]

Hi Ashok,

These variables are indeed global. They are meant to facilitate deep 
function calls that don't have a reference to the configuration.
I see how they can be a problem when you are using the library with 
multiple contexts.
May I suggest you create the different contexts in different processes 
(e.g., fork)?

If you don't care about using the different contexts in parallel, a 
context that finalizes its configuration (e.g., by resolving for the 
first time) will overwrite these values. Forking is not required then.

Hope that helps.

Best regards,
-- George

On 18/05/2022 17:05, ashok athukuri wrote:
> Hello Everyone,
> 
> Can anyone  guide me here ?
> 
> Thanks,
> Ashok
> 
> On Fri, May 13, 2022 at 3:51 PM ashok athukuri <athukuriashok at gmail.com 
> <mailto:athukuriashok at gmail.com>> wrote:
> 
>     Hello George,
> 
> 
>     Thanks for the quick response, Yes I am using libunbound version 1.12
> 
>     Yes I am setting config for a separate context
> 
>     but SERVE_EXPIRED_REPLY_TTL  is a global variable and the same is used in different places example dns.c tomsg() function
>     I feel because of this global variable this part of the code is creating problems for different cache conf.
>     I tested with multiple caches and its holding only 1 configuration (I doubt it because of code services/cache/dns.c#594)
> 
> 
>     SERVE_EXPIRED_REPLY is assigned in build/util/config_file.c#2056 (config_apply)2056  	
> 
>     SERVE_EXPIRED_REPLY_TTL = (time_t)config->serve_expired_reply_ttl;
> 
> 
>     below code tomsg() is depending on SERVE_EXPIRED_REPLY_TTL to make this works these variables should be set in the context before actually calling tomsg() function.
> 
>     Else these values may remain un changed and apply for all caches.
> 
>     As you can see in the below code services/cache/dns.c#594
>     589  	msg = gen_dns_msg(region, q, r->rrset_count);
> 
>     590  	if(!msg) return NULL;
> 
>     591  	msg->rep->flags = r->flags;
> 
>     592  	msg->rep->qdcount = r->qdcount;
> 
>     593  	msg->rep->ttl = is_expired
> 
>     594  		?SERVE_EXPIRED_REPLY_TTL
> 
>     595  		:r->ttl - now;
> 
>     596  	if(r->prefetch_ttl > now)
> 
>     597  		msg->rep->prefetch_ttl = r->prefetch_ttl - now;
> 
>     598  	else
> 
>     599  		msg->rep->prefetch_ttl = PREFETCH_TTL_CALC(msg->rep->ttl);
> 
>     600  	msg->rep->serve_expired_ttl = msg->rep->ttl + SERVE_EXPIRED_TTL;
> 
> 
>     Thanks,
> 
>     Ashok
> 
> 
> 
>     On Fri, May 13, 2022 at 3:07 PM George Thessalonikefs via
>     Unbound-users <unbound-users at lists.nlnetlabs.nl
>     <mailto:unbound-users at lists.nlnetlabs.nl>> wrote:
> 
>         Hi Ashok,
> 
>         The Unbound daemon runs as one cache resolver.
>         Are you perhaps using libunound and creating your own contexts?
>         In that case yes the options are per context.
>         You can have different options per context though, if you use the
>         'ub_ctx_set_option' function.
>         Since the options you mention are configurable and not hard
>         coded, the
>         aforementioned function works on them.
> 
>         Best regards,
>         -- George
> 
>         On 13/05/2022 07:25, ashok athukuri via Unbound-users wrote:
>          > Hello All,
>          >
>          > I am a newbie for unbound, please apologize if my question is
>         wrong or
>          > my understanding is wrong.
>          >
>          > I see below variables make unbound to use a
>         single configuration for all
>          > cache resolvers.
>          > As these variables are global and don't bind with any unbound
>         context or
>          > configuration for each cache
>          >
>          > I wonder how to solve this problem? as I need different cache
>         conf for
>          > different cache resolvers.
>          >
>          > 64 
>           <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#64 <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#64>>/** If we serve expired entries and prefetch them */
>          > 65 
>           <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#65 <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#65>>THREAD  <https://indexing2.f5net.com/source/s?defs=THREAD&project=tmos-dns-bugs <https://indexing2.f5net.com/source/s?defs=THREAD&project=tmos-dns-bugs>>  *int*  SERVE_EXPIRED  <https://indexing2.f5net.com/source/s?refs=SERVE_EXPIRED&project=tmos-dns-bugs <https://indexing2.f5net.com/source/s?refs=SERVE_EXPIRED&project=tmos-dns-bugs>>  = 0;
>          > 66 
>           <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#66 <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#66>>/** Time to serve records after expiration */
>          > 67 
>           <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#67 <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#67>>THREAD  <https://indexing2.f5net.com/source/s?defs=THREAD&project=tmos-dns-bugs <https://indexing2.f5net.com/source/s?defs=THREAD&project=tmos-dns-bugs>>  time_t  <https://indexing2.f5net.com/source/s?defs=time_t&project=tmos-dns-bugs <https://indexing2.f5net.com/source/s?defs=time_t&project=tmos-dns-bugs>>  SERVE_EXPIRED_TTL  <https://indexing2.f5net.com/source/s?refs=SERVE_EXPIRED_TTL&project=tmos-dns-bugs <https://indexing2.f5net.com/source/s?refs=SERVE_EXPIRED_TTL&project=tmos-dns-bugs>>  = 0;
>          > 68 
>           <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#68 <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#68>>/** TTL to use for expired records */
>          > 69 
>           <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#69 <https://indexing2.f5net.com/source/xref/tmos-dns-bugs/ports/unbound/build/util/data/msgreply.c#69>>THREAD  <https://indexing2.f5net.com/source/s?defs=THREAD&project=tmos-dns-bugs <https://indexing2.f5net.com/source/s?defs=THREAD&project=tmos-dns-bugs>>  time_t  <https://indexing2.f5net.com/source/s?defs=time_t&project=tmos-dns-bugs <https://indexing2.f5net.com/source/s?defs=time_t&project=tmos-dns-bugs>>  SERVE_EXPIRED_REPLY_TTL  <https://indexing2.f5net.com/source/s?refs=SERVE_EXPIRED_REPLY_TTL&project=tmos-dns-bugs <https://indexing2.f5net.com/source/s?refs=SERVE_EXPIRED_REPLY_TTL&project=tmos-dns-bugs>>  =30;
>          >
>          >
>          > Thanks,
>          >
>          > Ashok
>          >
>