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Top Forums UNIX for Advanced & Expert Users Interpretation of Ping behaviour Post 302921802 by jim mcnamara on Monday 20th of October 2014 11:21:34 AM
Old 10-20-2014
/etc/resolv.conf just enumerates the order and names of dns servers to check. You
may need to modify that. We use several dns servers in out network - two infoblox appliances and one windows domain controller.

As Made_in_Germany said, /etc/nsswitch.conf controls where to look in general.

Is your cache name service daemon running? Turn on dns caching.

Code:
/fmd> svcs /system/name-service-cache
STATE          STIME    FMRI
online         Oct_17   svc:/system/name-service-cache:default

Should say 'online'

Next check performance of the caching with
Code:
nscd -g

You want to see:
Code:
CACHE: hosts

         CONFIG:
         enabled: yes
         per user cache: no
         avoid name service: no
         check file: yes
         check file interval: 0
         positive ttl: 3600
         negative ttl: 5
         keep hot count: 20
         hint size: 2048
         max entries: 0 (unlimited)

         STATISTICS:
         positive hits: 39
         negative hits: 2
         positive misses: 2
         negative misses: 3
         total entries: 2
         queries queued: 0
         queries dropped: 0
         cache invalidations: 0
         cache hit rate:       89.1


CACHE: ipnodes

         CONFIG:
         enabled: yes
         per user cache: no
         avoid name service: no
         check file: yes
         check file interval: 0
         positive ttl: 3600
         negative ttl: 5
         keep hot count: 20
         hint size: 2048
         max entries: 0 (unlimited)

         STATISTICS:
         positive hits: 1104
         negative hits: 2
         positive misses: 25
         negative misses: 3
         total entries: 4
         queries queued: 0
         queries dropped: 0
         cache invalidations: 18
         cache hit rate:       97.5

You may need to increase your local dns cache size. Primarily what you need is a sysadmin/network admin who knows this stuff, and is not following a rote playbook for how to maintain a network.

The optimal solution for dns problems like this is most often to set up caching DNS servers, and turn off nscd.

As a side note, it is very slightly possible your cache is becoming stale, possibly a DNS server has problems. If the cache stuff is working you may want to bounce the nscd process. This will clear the caches. So if an immediate rerun of your problem continues, then you have other issues, which IMO tend to be nasty.

N.B.:
This kind of advice is hard to give without actually being there, too many moving parts to do a decent job vicariously like this.
 

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AnyEvent::XMPP::Ext::Ping(3pm)				User Contributed Perl Documentation			    AnyEvent::XMPP::Ext::Ping(3pm)

NAME
AnyEvent::XMPP::Ext::Ping - Implementation of XMPP Ping XEP-0199 SYNOPSIS
use AnyEvent::XMPP::Ext::Ping; my $con = AnyEvent::XMPP::IM::Connection->new (...); $con->add_extension (my $ping = AnyEvent::XMPP::Ext::Ping->new); # this enables auto-timeout of a connection if it didn't answer # within 120 seconds to a ping with a reply $ping->enable_timeout ($con, 120); my $cl = AnyEvent::XMPP::Client->new (...); $cl->add_extension (my $ping = AnyEvent::XMPP::Ext::Ping->new); # this enables auto-timeout of newly created connections $ping->auto_timeout(120); $ping->ping ($con, 'ping_dest@server.tld', sub { my ($time, $error) = @_; if ($error) { # we got an error } # $time is a float (seconds) of the rtt if you got Time::HiRes }); DESCRIPTION
This extension implements XEP-0199: XMPP Ping. It allows you to define a automatic ping timeouter that will disconnect dead connections (which didn't reply to a ping after N seconds). See also the documentation of the "enable_timeout" method below. It also allows you to send pings to any XMPP entity you like and will measure the time it took if you got Time::HiRes. METHODS
new (%args) Creates a new ping handle. auto_timeout ($timeout) This method enables automatic connection timeout of new connections. It calls "enable_timeout" (see below) for every new connection that was connected and emitted a "stream_ready" event. This is useful if you want connections that have this extension automatically timeouted. In particular this is useful with modules like AnyEvent::XMPP::Client (see also SYNOPSIS above). enable_timeout ($con, $timeout) This enables a periodical ping on the connection $con. $timeout must be the seconds that the ping intervals last. If the server which is connected via $con didn't respond within $timeout seconds the connection $con will be disconnected. Please note that there already is a basic timeout mechanism for dead TCP connections in AnyEvent::XMPP::Connection, see also the "whitespace_ping_interval" configuration variable for a connection there. It then will depend on TCP timeouts to disconnect the connection. Use "enable_timeout" and "auto_timeout" only if you really feel like you need an explicit timeout for your connections. ping ($con, $dest, $cb, $timeout) This method sends a ping request to $dest via the AnyEvent::XMPP::Connection in $con. If $dest is undefined the ping will be sent to the connected server. $cb will be called when either the ping timeouts, an error occurs or the ping result was received. $timeout is an optional timeout for the ping request, if $timeout is not given the default IQ timeout for the connection is the relevant timeout. The first argument to $cb will be the seconds of the round trip time for that request (If you have Time::HiRes). If you don't have Time::HiRes installed the first argument will be undef. The second argument to $cb will be either undef if no error occured or a AnyEvent::XMPP::Error::IQ error object. ignore_pings ($bool) This method is mostly for testing, it tells this extension to ignore all ping requests and will prevent any response from being sent. AUTHOR
Robin Redeker, "<elmex at ta-sa.org>", JID: "<elmex at jabber.org>" COPYRIGHT &; LICENSE Copyright 2007, 2008 Robin Redeker, all rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. perl v5.14.2 2012-01-23 AnyEvent::XMPP::Ext::Ping(3pm)
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