NAME¶
gdnsd-plugin-metafo - gdnsd plugin for address meta-failover
SYNOPSIS¶
Minimal example gdnsd config file using this plugin:
plugins => {
metafo => {
resources => {
prod_www => {
datacenters => [ dc-01, dc-02, dc-03 ]
dcmap => {
dc-01 => 192.0.2.1
dc-02 => { lb01 => 192.0.2.2, lb02 => 192.0.2.3 }
dc-03 => [ 192.0.2.4, 192.0.2.5, 192.0.2.6 ]
}
},
prod_foo => {
datacenters => [ dc-01, dc-02, dc-bk ]
dcmap => {
dc-01 => { lb01 => 192.0.1.1, lb02 => 192.0.1.2 }
dc-02 => [ 192.0.5.1, 192.0.5.2, 192.0.5.3 ]
dc-bk => fallback.static.cname.example.com.
}
}
}
}
}
Example zonefile RRs:
www 600 DYNA metafo!prod_www
www-dc01 600 DYNA metafo!prod_www/dc-01
foo 700 DYNC metafo!prod_foo
DESCRIPTION¶
gdnsd-plugin-metafo is a meta-plugin. It does static-ordered address
failover between multiple "datacenters" (which may or may not
correspond with real datacenters, it's just a convenient label). Each
datacenter is defined in terms of other plugins such as "multifo",
"weighted", etc, as described below.
CONFIGURATION - TOP-LEVEL¶
The top level of the metafo plugin's configuration (i.e. "plugins => {
metafo => { ... } }") supports only one fixed, required key,
"resources", whose value must be a hash. The contents of
"resources" is a key per named resource, with the value defining
that resource.
Any other keys present at the top level will be inherited down inside of each
per-resource hash inside the "resources" stanza, acting as
per-resource defaults for anything not defined explicitly there, as explained
below.
CONFIGURATION - RESOURCES¶
All keys within the resources stanza represent named resources, which can be
referenced by "DYNA" RRs in zonefiles (e.g. "www DYNA
metafo!resource_name"). Each resource's value must be a key-value hash
configuring the resource itself. Lightweight structural example:
plugins => {
metafo => {
resources => { resA => { ... }, resB => { ... } }
}
}
Within a resource, there are only two specifically meaningful keys:
- "datacenters = [ A, B, C, ... ]"
- Array of datacenter names, required. This is the set of datacenter name
labels used for this resource, in the order they will be checked for
failover.
- "dcmap = { ... }"
- Hash, required. The "dcmap" is a key-value hash where the keys
must be exactly the list of datacenters defined in this resource's
"datacenters" list, and the values defined the address
configuration of each datacenter. Another minimal structural example down
to this level:
plugins => {
metafo => {
resources => {
resA => {
datacenters => [ dc01, dc02 ],
dcmap => {
dc01 => ???
dc02 => ???
}
}
}
}
}
There are several forms the per-datacenter values ("???" above)
can take, documented in the next section.
Any keys other than "datacenters" and "dcmap" at the
per-resource level serve as inherited defaults for each per-datacenter
configuration inside of the "dcmap".
PER-DATACENTER RESOLUTION¶
The value of the datacenters within the "dcmap" section of a resource
can take several forms. It is important to understand that for the most part,
plugin_metafo does not deal with this level of results itself, but instead
delegates the work at this scope to other plugins. These sub-plugins, in turn,
also notify metafo of complete failure at their level, which is the
information metafo uses to know to fail over to the next datacenter in the
list.
The most direct and obvious way to do this is with a direct reference of the
form "%plugin!resource", as shown here:
plugins => {
metafo => {
resources => {
resA => {
datacenters => [ dc1, dc2 ],
dcmap => {
dc1 => %multifo!res_mfo1
dc2 => %multifo!res_mfo2
}
}
}
}
multifo => {
res_mfo1 => { lb01 => 192.0.2.1, lb02 => 192.0.2.3 }
res_mfo2 => { lb01 => 192.0.2.111, lb02 => 192.0.2.113 }
}
}
However, to make life simpler in the simple cases, plugin_metafo can synthesize
the lower-level plugin's configuration from a hash, like so:
plugins => {
metafo => {
resources => {
resA => {
datacenters => [ dc1, dc2 ],
dcmap => {
dc1 => { plugin => multifo, lb01 => 192.0.2.1, lb02 => 192.0.2.3 }
dc2 => { lb01 => 192.0.2.111, lb02 => 192.0.2.113 }
# the above are effectively treated as:
# dc1 => %multifo!metafo_resA_dc1
# dc2 => %multifo!metafo_resA_dc2
}
}
}
}
# below does not exist in your configfile, but is what plugin_metafo
# synthesizes to support the above:
#multifo => {
# metafo_resA_dc1 => { lb01 => 192.0.2.1, lb02 => 192.0.2.3 }
# metafo_resA_dc2 => { lb01 => 192.0.2.111, lb02 => 192.0.2.113 }
#}
}
Within a hash like the above, the special key "plugin" will be
stripped out internally and used to name the plugin we synthesize the config
for. "plugin" defaults to "multifo" if not specified. Note
that "plugin" could also be specified at the resource level (just
inside of the "resA" stanza) to change the default for all
"dcmap" entries in one resource, and could also be specified at the
outer-most scope (just inside the "metafo" stanza) to change the
default for all resources.
The defaulted-down "plugin" is also the default for the
direct-reference "%plugin!resource" form discussed earlier. With the
correct default plugin name, it can be shortened to just
"!resource".
The same sort of key-value inheritance scheme (top-level -> per-resource
level -> per-datacenter level) can also be used for any other parameter in
synthesized resource configurations specific to the per-datacenter plugin(s)
you are using. A common example would be the "service_types"
parameter that most plugins which support monitored address results have. Note
that these other values (e.g. service_types) would only apply to synthesized
resources,
not to direct-references like "%multifo!foo",
which must be configured entirely separately within that plugin's config.
There are three other possible shortcut values for datacenters: a single direct
address, an array of addresses, or a single CNAME hostname. If a single IP
address or an array of IP addresses are specified, plugin_metafo will
synthesize a hash from them with the plugin forced to "multifo"
(since it cannot know the syntax of hashes for all other plugins, which may
differ), and give them address labels 1, 2, etc.
If the value for a datacenter is a single CNAME hostname, no sub-plugin is used,
and that CNAME result is returned directly. Note that any resource with such
an entry can only be used with "DYNC" RRs, and not "DYNA"
RRs (as is the case if any subplugin's configuration is capable of returning
CNAME data).
A much more complete example, showing off most of the features above:
plugins => {
metafo => {
plugin => multifo # change default for all resources
service_types => [ bar ] # default service_types for synthesized below
resources => {
resA => {
plugin => multifo # change default for this resource
service_types => [foo, bar] # services types for synthesized below:
datacenters => [ dc1, dc2, dc3, dc4, dc5, dc6, dc7, dc8 ],
dcmap => {
dc1 => { plugin => multifo, lb01 => 192.0.2.1, lb02 => 192.0.2.3 }
dc2 => { lb01 => 192.0.2.111, lb02 => 192.0.2.113 }
dc3 => %simplefo!foo
dc4 => { plugin => simplefo, primary => 192.0.2.100, secondary => 192.0.2.101 }
dc5 => !bar
dc6 => 192.0.2.150
dc7 => [ 192.0.2.180, 192.0.2.181 ]
dc8 => last.resort.example.com.
}
}
}
}
# below, commented-out sections show configuration synthesized
# by plugin_metafo, whereas the rest are direct-references that
# had to be manually specified here:
multifo => {
# metafo_resA_dc1 => { lb01 => 192.0.2.1, lb02 => 192.0.2.3, service_types => [foo, bar] }
# metafo_resA_dc2 => { lb01 => 192.0.2.111, lb02 => 192.0.2.113, service_types => [foo, bar] }
bar => { asd => 192.0.2.77, xyz => 192.0.2.88 }
# metafo_resA_dc6 => { 1 => 192.0.2.150, service_types => [foo, bar] }
# metafo_resA_dc7 => { 1 => 192.0.2.180, 2 => 192.0.2.181, service_types => [foo, bar] }
}
simplefo => {
foo => { primary => 192.0.2.80, secondary => 192.0.2.81 }
# metafo_resA_dc4 => { primary => 192.0.2.100, secondary => 192.0.2.101, service_types => [foo, bar] }
}
}
Note in the example above that "%multifo!bar" and
"%simplefo!foo" would have had their default "service_types =
up" rather than the one specified at the metafo level, because they were
not synthesized. It would be up to you to keep all of the service_types in
sync when using direct references.
SYNTHETIC PER-DATACENTER RESOURCES¶
This plugin will synthesize additional, per-datacenter resource names from your
configuration. They are named as "resname/dcname". For example, if
you define a metafo resource named "prodwww" with the datacenter
list "[ pri, sec ]", the resource names "prodwww/pri" and
"prodwww/sec" will be sythesized and can be used in zonefile
records, e.g.:
www-backup 300 DYNA metafo!prodwww/sec
When used, these per-datacenter synthetic resource names cause a given lookup to
skip the normal failover process and directly return results from that
particular datacenter.
SEE ALSO¶
gdnsd.config(5),
gdnsd.zonefile(5),
gdnsd(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/>.