Dependency problem

[Tedman Eng]

Try lowering the host max_check_attempts.  When nagios detects a service is
bad, it'll hostcheck each parent up the tree and will not do ANYTHING for
the 30 check attempts you've set while it tries to determine whether RT1,
RT2, and/or RT3 is down.  This can adversely affect your other monitored
devices if those links are always flapping.  It's better to monitor faster
and make notifications slower than to slow down the entire monitoring.  The
host will show up in the console as up/down/flapping a lot, which is its
true state.  You can artificially slow down notifications by using
escalations.
 
For example:
set notification interval to 5
set no contact for the normal notification (use the escalation instead)
set the escalation to notify starting at alert #2
 
This would in effect make it so the device would have to be down for a full
5 minutes before you get notified.
 
 
 
 -----Original Message-----
From: Anastasios Zafeiropoulos [mailto:mls at freemail.gr]
Sent: Wednesday, April 07, 2004 12:59 PM
To: nagios-users
Subject: [Nagios-users] Dependency problem



Hello world,
 
I'm having trouble with a Host dependency misconfiguration or why not, with
a bug in Nagios' Dependency logic process and 
 
notification.
 
I am using version nagios-1.2-0.rhfc1.dag which was a prebuilt package from
Dag Apt repository site.
===================================================
My Topology:
===================================================
 
Nagios machine --- RT1 -- RT2 -- RT3 
 


====================================================
The problem
====================================================
 
When RT1 goes down, or the RT1-RT2 Link goes down, Nagios will notice that
at random, while he is checkong a service or 
 
HOST_ALIVE function to any part of the network that is down. Let's assume
that the first Host that Nagios found dead was RT3. 
 
Nagios didn't get any reply from RT3, so RT3 will be kept in SOFT down
state. 
 
Next the RETRY proccess will take place. The max_check_attempts are 30 for
each host. That's because the links are not 
 
reliable at all so we want to be a little elastic with the Notifications.
 
At the time that we reach the Retry #30, Nagios assumes that RT3 IS DOWN,
puts it in HARD DOWN state and looks to find any 
 
dependencies associated with the RT3. If you look below, RT3 is dependent
upon RT2. So it will continue with try pinging RT2.
 
While Nagios is trying to determine whether the RT2 is alive or not,
suddendly, the RT1-RT2 link comes up and all the network 
 
is now reachable by Nagios. I notice here that the max_checks_attempts
havent timed out. So Nagios will take a response from 
 
RT2 and it will put it in A HARD OK State.
 
The result will be NOT to check RT3 again to see if he is up as RT2. So, a
notification will be sent reporting that RT3 is 
 
down. This is FAKE. The whole network was down!
 
Below I provide you my configuration. Maybe sth goes wrong with my conf
files.
 
Thanks in advance guys
 
====================================================
My dependecies.cfg file
====================================================
 
define hostdependency{
 host_name   RT2
 dependent_host_name  RT3
 notification_failure_criteria d,u
 }
 
define hostdependency{
 host_name   RT1
 dependent_host_name  RT2
 notification_failure_criteria d,u
 }
 

===================================================
My hosts.cfg
===================================================
 
define host{
 use   generic-host
 host_name  RT1
 alias   Wireless 1
 address   213.5.0.34
 check_command  check-host-alive
 max_check_attempts  30
 notification_interval 0
 notification_period 24x7
 notification_options d,u
 }
 

define host{
 use   generic-host
 host_name  RT2
 alias   tsapi.twmn
 address   10.107.13.1
 parents   RT1
 check_command  check-host-alive
 max_check_attempts  30
 notification_interval 0
 notification_period 24x7
 notification_options d,u
 }
 

define host{
 use   generic-host
 host_name  RT3
 alias   Wireless Internet
 address   212.34.23.4
 parents   RT2
 check_command  check-host-alive
 max_check_attempts  30
 notification_interval 0
 notification_period 24x7
 notification_options d,u
 }
 
 

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