Re: [Evolution] 3.16.3: Failed to refresh folder "INBOX",

[Pete Biggs <pete biggs org uk>]

On Tue, 2015-06-23 at 17:53 -0600, Zan Lynx wrote:
> On 06/23/2015 02:24 AM, Pete Biggs wrote:
> > Don't get confused by using utilities such as nslookup - they 
> > perform
> > the DNS queries themselves so by-pass the cache.
>
> Only if you tell them to do so. By default dig and nslookup do the query
> to the same resolver IP that the system libraries use.

This isn't the place to argue about DNS lookups.  But yes, they use the
same DNS server by default, but nslookup doesn't use the system name
services for the query, it talks directly to the DNS servers.  Hence it
by-passes any system cache, which was my point. I can see it doing it
using strace and you can change the DNS server it queries from within
the program so it can't just hand off the queries to the OS.

> If there is a cache in use, it is inside the Evolution libraries. 

No, as Milan said, Evolution doesn't cache the queries, all such
network activities are handled by other libraries.

>  If a
> command-line ping, dig, or host command returns the new IP for a DNS
> name, Evolution should be using that as well.

Not necessarily, it depends on the individual libraries being used.


> If it does not, that would be a bug.

Not necessarily.  The DNS entry has a lifetime, it is not at all
unreasonable for the client to assume that the name<->IP mapping is
valid for the entirety of the "lifetime".  That's the whole point of it
- i.e. to reduce the number of DNS queries necessary by caching the
results.

P.