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db0b16b615
Add a ready plugin that allows plugin to signal when they are ready.
Once a plugin is ready it is not queried again.
This uses same mechanism as the health plugin: each plugin needs to
implement an interface.
Implement readines for the *erratic* plugin to aid in testing.
Add README.md and tests moduled after the health plugin; which will be
relegated to just providing process health. In similar vein to health
this is a process wide setting.
With this Corefile:
~~~
. {
erratic
whoami
ready
}
bla {
erratic
whoami
}
~~~
ready will lead to:
~~~ sh
% curl localhost:8181/ready
% dig @localhost -p 1053 mx example.org
% curl localhost:8181/ready
OK%
~~~
Meanwhile CoreDNS logs:
~~~
.:1053
bla.:1053
2019-02-26T20:59:07.137Z [INFO] CoreDNS-1.3.1
2019-02-26T20:59:07.137Z [INFO] linux/amd64, go1.11.4,
CoreDNS-1.3.1
linux/amd64, go1.11.4,
2019-02-26T20:59:11.415Z [INFO] plugin/ready: Still waiting on: "erratic"
2019-02-26T20:59:13.510Z [INFO] plugin/ready: Still waiting on: "erratic"
~~~
*ready* can be used in multiple server blocks and will do the right
thing; query all those plugins from all server blocks for readiness.
This does a similar thing to the prometheus plugin.
Signed-off-by: Miek Gieben <miek@miek.nl>
98 lines
1.9 KiB
Markdown
98 lines
1.9 KiB
Markdown
# erratic
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## Name
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*erratic* - a plugin useful for testing client behavior.
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## Description
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*erratic* returns a static response to all queries, but the responses can be delayed, dropped or truncated.
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The *erratic* plugin will respond to every A or AAAA query. For any other type it will return
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a SERVFAIL response. The reply for A will return 192.0.2.53 (see [RFC
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5737](https://tools.ietf.org/html/rfc5737),
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for AAAA it returns 2001:DB8::53 (see [RFC 3849](https://tools.ietf.org/html/rfc3849)) and for an
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AXFR request it will respond with a small zone transfer.
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*erratic* can also be used in conjunction with the *autopath* plugin. This is mostly to aid in
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testing.
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## Syntax
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~~~ txt
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erratic {
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drop [AMOUNT]
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truncate [AMOUNT]
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delay [AMOUNT [DURATION]]
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}
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~~~
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* `drop`: drop 1 per **AMOUNT** of queries, the default is 2.
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* `truncate`: truncate 1 per **AMOUNT** of queries, the default is 2.
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* `delay`: delay 1 per **AMOUNT** of queries for **DURATION**, the default for **AMOUNT** is 2 and
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the default for **DURATION** is 100ms.
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In case of a zone transfer and truncate the final SOA record *isn't* added to the response.
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## Health
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This plugin implements dynamic health checking. For every dropped query it turns unhealthy.
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## Ready
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This plugin reports readiness to the ready plugin.
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## Examples
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~~~ corefile
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. {
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erratic {
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drop 3
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}
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}
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~~~
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Or even shorter if the defaults suits you. Note this only drops queries, it does not delay them.
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~~~ corefile
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. {
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erratic
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}
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~~~
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Delay 1 in 3 queries for 50ms
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~~~ corefile
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. {
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erratic {
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delay 3 50ms
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}
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}
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~~~
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Delay 1 in 3 and truncate 1 in 5.
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~~~ corefile
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. {
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erratic {
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delay 3 5ms
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truncate 5
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}
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}
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~~~
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Drop every second query.
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~~~ corefile
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. {
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erratic {
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drop 2
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truncate 2
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}
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}
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~~~
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## Also See
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[RFC 3849](https://tools.ietf.org/html/rfc3849) and
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[RFC 5737](https://tools.ietf.org/html/rfc5737).
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