metadata

metadata enable a meta data collector.

Description

By enabling metadata any plugin that implements metadata.Provider interface 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 and the package level documentation.