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plugin/metadata: finish documentation (#1951)

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* plugin/metadata: finish documentation

Finish the README.md, add corner case in the IsLabel test and reword
some code comments slightly.

Generate the man-pages and add man/coredns-metadata.7 as well.

Signed-off-by: Miek Gieben <miek@miek.nl>

* Fix test

Signed-off-by: Miek Gieben <miek@miek.nl>
This commit is contained in:
Miek Gieben
2018-07-09 07:58:14 +01:00
committed by GitHub
parent b3a92f1622
commit b27a59c160
5 changed files with 86 additions and 15 deletions
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21
plugin/metadata/README.md
View File

@@ -8,15 +8,20 @@
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
each DNS query, at beginning of the process for that query, in order to add it's own meta data 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.
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.
TODO: write about naming of the keys (labels).
TODO: write about extracting and using
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
@@ -28,7 +33,7 @@ metadata [ZONES... ]
## Plugins
metadata.Provider interface needs to be implemented by each plugin willing to provide metadata
`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.
@@ -36,7 +41,7 @@ Note: this method should work quickly, because it is called for every request.
## Examples
There are currently no in tree plugins that write or use metadata.
The *rewrite* plugin uses meta data to rewrite requests.
## Also See

7
plugin/metadata/metadata_test.go
View File

@@ -68,20 +68,23 @@ func TestLabelFormat(t *testing.T) {
label string
isValid bool
}{
// ok
{"plugin/LABEL", true},
{"p/LABEL", true},
{"plugin/L", true},
// fails
{"LABEL", false},
{"plugin.LABEL", false},
{"/NO-PLUGIN-NOT-ACCEPTED", false},
{"ONLY-PLUGIN-NOT-ACCEPTED/", false},
{"PLUGIN/LABEL/SUB-LABEL", false},
{"/", false},
{"//", false},
}
for _, test := range labels {
if IsLabel(test.label) != test.isValid {
t.Errorf("Label %v is expected to have this validaty : %v - and has the opposite", test.label, test.isValid)
if x := IsLabel(test.label); x != test.isValid {
t.Errorf("Label %v expected %v, got: %v", test.label, test.isValid, x)
}
}
}

2
plugin/metadata/provider.go
View File

@@ -49,7 +49,7 @@ type Provider interface {
// Func is the type of function in the metadata, when called they return the value of the label.
type Func func() string
// IsLabel check that the provided name looks like a valid label name
// IsLabel checks that the provided name is a valid label name, i.e. two words separated by a slash.
func IsLabel(label string) bool {
p := strings.Index(label, "/")
if p <= 0 || p >= len(label)-1 {