mirror of
https://github.com/coredns/coredns.io.git
synced 2024-04-21 12:32:00 +00:00
Miek Gieben
9d3c78f16f
Make notes in coredns' repo to make it authoritative there. Signed-off-by: Miek Gieben <miek@miek.nl>
53 lines
1.8 KiB
Markdown
53 lines
1.8 KiB
Markdown
+++
|
|
title = "metadata"
|
|
description = "*metadata* enable a meta data collector."
|
|
weight = 23
|
|
tags = [ "plugin", "metadata" ]
|
|
categories = [ "plugin" ]
|
|
date = "2019-03-03T14:11:50.604079"
|
|
+++
|
|
|
|
## 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 beginning of the process for that query, in order to add it's own meta data to
|
|
context.
|
|
|
|
The meta data 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.
|
|
|
|
The meta data is added by setting a label with a value in the context. These labels should be named
|
|
`plugin/NAME`, where **NAME** is something descriptive. The only hard requirement the *metadata*
|
|
plugin enforces is that the labels contains a slash. See the documentation for
|
|
`metadata.SetValueFunc`.
|
|
|
|
The value stored is a string. The empty string signals "no meta data". See the documentation for
|
|
`metadata.ValueFunc` on how to retrieve this.
|
|
|
|
## Syntax
|
|
|
|
~~~
|
|
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.
|
|
|
|
## Examples
|
|
|
|
The *rewrite* plugin uses meta data to rewrite requests.
|
|
|
|
## Also See
|
|
|
|
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.
|