GDNSD-PLUGIN-MULTIFO(8) gdnsd GDNSD-PLUGIN-MULTIFO(8)NAMEgdnsd-plugin-multifo - gdnsd plugin for multi-address, all-active
failover groups
SYNOPSIS
Example plugin config:
plugins => {
multifo => {
up_thresh => 0.3
service_types => default,
v4www => {
lb01 => 192.0.2.200,
lb02 => 192.0.2.201,
lb03 => 192.0.2.202,
}
v6smtp => {
service_types => [ smtp ],
up_thresh => 0.1,
lb01_v6 => 2001:DB8::1,
lb02_v6 => 2001:DB8::2,
lb03_v6 => 2001:DB8::3,
}
pubwww => {
up_thresh => 0.5
service_types => [ corpwww_type, default ],
addrs_v4 => [ 192.0.2.100, 192.0.2.101, 192.0.2.102 ]
addrs_v6 => {
service_types => [ up ],
up_thresh => 0.7
lb01_v6 => 2001:DB8::1,
lb02_v6 => 2001:DB8::2,
lb03_v6 => 2001:DB8::3,
}
}
}
}
Example zonefile RRs:
web4 180 DYNA multifo!v4www
smtp 180 DYNA multifo!v6smtp
www 180 DYNA multifo!pubwww
DESCRIPTIONgdnsd-plugin-multifo is designed to do multi-address all-active
failover grouping. Basically, for each configured resource name, you
supply a labeled list of addresses. multifo monitors these addresses
according to "service_types", and answers "DYNA" address queries using
the non-"DOWN" subset. The core gdnsd code will round-robin rotate the
records on the way out, as it does for all address RR-sets.
TOP-LEVEL PLUGIN CONFIG
At the top level of the plugin's configuration stanza, two special
parameters "up_thresh" and "service_types" are supported. These set
default per-resource options of the same name for any resources which
do not define them explicitly.
The rest of the hash entries at the top level are the names of the
resources you define. Each resource gets a configuration hash of its
own for containing resource-specific parameters as well as the actual
address data.
RESOURCE CONFIG
Within a resource, you have two basic options. You can either directly
specify a set of "label => address" pairs which are all the same family
(IPv4 or IPv6), or you can use the sub-stanzas "addrs_v4" and/or
"addrs_v6" to specify one or both families in the same resource.
The "up_thresh" and "service_types" parameters are inherited through
every level, and can be overridden at any level (even per-address-
family):
up_thresh
Floating point, default 0.5, range (0.0 - 1.0]. This configures
the per-resource "up_thresh" threshold. More details in "UP
THRESH" below.
service_types
Array of strings, or single string. Default "default". This sets
the monitored service_types for this resource. If an array of more
than one is provided, all will be monitored for each address, and
the net monitored state will be the minimum (worst) of the set.
See gdnsd.config(8) for more details on service_types.
SHORTCUT CONFIG
If you have no parameters (service_types, up_thresh) to configure in a
given stanza (single-family direct resource config, or addrs_v[46]),
and do not care about the descriptive per-address labels used in
monitoring, you can replace the hash with an array of addresses. The
labels will be generated for you as a series of integers starting with
1. For example, the following are equivalent:
res1 => { addrs_v4 => [ 192.0.2.1, 192.0.2.2 ] }
res1 => { addrs_v4 => { 1 => 192.0.2.1, 2 => 192.0.2.2 } }
OPERATIONAL MECHANICS
All of the addresses for all of the resources are monitored using the
per-address-family inherited "service_types" specified (default would
be simple HTTP/1.0 monitoring for "200 OK" on port 80). When the core
daemon requests a lookup for address records of a given family on one
of this plugin's resources, it goes through essentially the following
process to determine the set of response addresses for that address
family: 1) Add all non-DOWN addresses to the result set. 2) If the set
of non-DOWN addresses fail the up_thresh check, add *all* addresses to
the result set as a fallback. 3) If any address is in the DOWN or even
DANGER state, cut the zonefile-specified TTL in half
This process is repeated independently for each of the IPv4 and IPv6
address subsets, in the case that a resource has both address families
configured (the TTL is only cut in half once of course). Details on
the up_thresh check follow:
UP THRESH
Any non-DOWN address is considered an acceptable result for up_thresh
purposes, even ones in the transitional DANGER state. If there are not
"enough" non-DOWN addresses to pass the threshold (per address family),
all addresses (of a given address family) will be returned as a
fallback.
The threshold is implemented mathematically as in the following pseudo-
code "if(non_down >= ceil(thresh * total)) threshold_passed;". For
example, if thresh is at the default value of 0.5, and there are 3
total IPv4 addresses, then 2 of them must be non-down to pass the
threshold. The net result is that with the default threshold, the
plugin will never return an isolated single address from a set of 3.
It will either return all 3, or it will return 2/3 if a single address
from the set has failed.
When the threshold check fails (and all addresses are returned) for
either address family, resource-level total failure will also be
signaled to any applicable upstream meta-plugins such as metafo or
geoip.
General rules for the results of the up_thresh formula:
· A threshold of 1.0 will only pass if all addresses are not-down.
This is mostly pointless, you might as well not monitor anything
and set up these addresses as a static set in a zonefile.
· A threshold of 0.01 will pass even if only one address is alive and
return just that one address, even if it's e.g. the only one left
out of 40.
· Because a threshold of 0.0 is illegal, if all addresses are down
the threshold will always fail, returning all addresses.
Intermediate value examples: (threshold: non-down/total required to
pass threshold):
· 0.1: 1/1 1/2 1/3 1/4 1/5 1/6 1/7 1/8 2/16
· 0.2: 1/1 1/2 1/3 1/4 1/5 2/6 2/7 2/8 4/16
· 0.3: 1/1 1/2 1/3 2/4 2/5 2/6 3/7 3/8 5/16
· 0.4: 1/1 1/2 2/3 2/4 2/5 3/6 3/7 4/8 7/16
· 0.5: 1/1 1/2 2/3 2/4 3/5 3/6 4/7 4/8 8/16
· 0.6: 1/1 2/2 2/3 3/4 3/5 4/6 5/7 5/8 10/16
· 0.7: 1/1 2/2 3/3 3/4 4/5 5/6 5/7 6/8 12/16
· 0.8: 1/1 2/2 3/3 4/4 4/5 5/6 6/7 7/8 13/16
· 0.9: 1/1 2/2 3/3 4/4 5/5 6/6 7/7 8/8 15/16
SEE ALSOgdnsd.config(5), gdnsd.zonefile(5), gdnsd(8), gdnsd-plugin-simplefo(8)
The gdnsd manual.
COPYRIGHT AND LICENSE
Copyright (c) 2012 Brandon L Black <blblack@gmail.com>
This file is part of gdnsd.
gdnsd is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation, either version 3 of the License, or (at your
option) any later version.
gdnsd is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License along
with gdnsd. If not, see <http://www.gnu.org/licenses/>.
gdnsd 1.11.0 2013-12-06 GDNSD-PLUGIN-MULTIFO(8)
