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plugin/metadata: adjust doc to latest code. (#1923)

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* plugin/metadata: adjust doc to latest code.

Signed-off-by: Miek Gieben <miek@miek.nl>
This commit is contained in:
Miek Gieben
2018-07-06 09:41:37 +01:00
committed by GitHub
parent 826d878084
commit 195fe5d1a4
1 changed files with 21 additions and 24 deletions
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45
plugin/metadata/README.md
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@@ -2,13 +2,21 @@
## Name
*metadata* - enable a metadata collector.
*metadata* - enable a meta data collector.
## Description
By enabling *metadata* any plugin that implements [metadata.Provider interface](https://godoc.org/github.com/coredns/coredns/plugin/metadata#Provider) will be called for each DNS query, at being of the process for that query, in order to add it's own Metadata to context. The metadata collected will be available for all plugins handler, via the Context parameter provided in the ServeDNS function.
Metadata plugin is automatically adding the so-called default medatada (extracted from the query) to the context. Those default metadata are: {qname}, {qtype}, {client_ip}, {client_port}, {protocol}, {server_ip}, {server_port}
By enabling *metadata* any plugin that implements [metadata.Provider
interface](https://godoc.org/github.com/coredns/coredns/plugin/metadata#Provider) will be called for
each DNS query, at beginning of the process for that query, in order to add it's own Metadata to
context.
The metadata collected will be available for all plugins, via the Context parameter
provided in the ServeDNS function. The package (code) documentation has examples on how to inspect
and retrieve metadata a plugin might be interested in.
TODO: write about naming of the keys (labels).
TODO: write about extracting and using
## Syntax
@@ -16,32 +24,21 @@ Metadata plugin is automatically adding the so-called default medatada (extracte
metadata [ZONES... ]
~~~
* **ZONES** zones metadata should be invoked for.
## Plugins
metadata.Provider interface needs to be implemented by each plugin willing to provide metadata information for other plugins. It will be called by metadata and gather the information from all plugins in context.
Note: this method should work quickly, because it is called for every request
from the metadata plugin.
If **ZONES** is specified then metadata add is limited by zones. Metadata is added to every context going through metadata.Provider if **ZONES** are not specified.
metadata.Provider interface needs to be implemented by each plugin willing to provide metadata
information for other plugins. It will be called by metadata and gather the information from all
plugins in context.
Note: this method should work quickly, because it is called for every request.
## Examples
Enable metadata for all requests. Rewrite uses one of the provided by default metadata variables.
There are currently no in tree plugins that write or use metadata.
~~~ corefile
. {
metadata
rewrite edns0 local set 0xffee {client_ip}
forward . 8.8.8.8:53
}
~~~
## Also See
Add metadata for all requests within `example.org.`. Rewrite uses one of provided by default metadata variables. Any other requests won't have metadata.
~~~ corefile
. {
metadata example.org
rewrite edns0 local set 0xffee {client_ip}
forward . 8.8.8.8:53
}
~~~
The [Provider interface](https://godoc.org/github.com/coredns/coredns/plugin/metadata#Provider) and
the [package level](https://godoc.org/github.com/coredns/coredns/plugin/metadata) documentation.