NAME¶
gdnsd-plugin-multifo - gdnsd plugin for multi-address, all-active failover
groups
SYNOPSIS¶
Example plugin config:
plugins => {
multifo => {
up_thresh => 0.3
service_types => up,
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
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
DESCRIPTION¶
gdnsd-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 the static virtual monitor "up"). 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 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¶
If there are not enough UP 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 ALSO¶
gdnsd.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/>.