traefik/pkg/config/env/env.go

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// Package env implements encoding and decoding between environment variable and a typed Configuration.
package env
import (
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"fmt"
"regexp"
"strings"
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"github.com/containous/traefik/v2/pkg/config/parser"
)
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// DefaultNamePrefix is the default prefix for environment variable names.
const DefaultNamePrefix = "TRAEFIK_"
// Decode decodes the given environment variables into the given element.
// The operation goes through four stages roughly summarized as:
// env vars -> map
// map -> tree of untyped nodes
// untyped nodes -> nodes augmented with metadata such as kind (inferred from element)
// "typed" nodes -> typed element
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func Decode(environ []string, prefix string, element interface{}) error {
if err := checkPrefix(prefix); err != nil {
return err
}
vars := make(map[string]string)
for _, evr := range environ {
n := strings.SplitN(evr, "=", 2)
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if strings.HasPrefix(strings.ToUpper(n[0]), prefix) {
key := strings.ReplaceAll(strings.ToLower(n[0]), "_", ".")
vars[key] = n[1]
}
}
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rootName := strings.ToLower(prefix[:len(prefix)-1])
return parser.Decode(vars, element, rootName)
}
// Encode encodes the configuration in element into the environment variables represented in the returned Flats.
// The operation goes through three stages roughly summarized as:
// typed configuration in element -> tree of untyped nodes
// untyped nodes -> nodes augmented with metadata such as kind (inferred from element)
// "typed" nodes -> environment variables with default values (determined by type/kind)
func Encode(element interface{}) ([]parser.Flat, error) {
if element == nil {
return nil, nil
}
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node, err := parser.EncodeToNode(element, parser.DefaultRootName, false)
if err != nil {
return nil, err
}
err = parser.AddMetadata(element, node)
if err != nil {
return nil, err
}
return parser.EncodeToFlat(element, node, parser.FlatOpts{Case: "upper", Separator: "_"})
}
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func checkPrefix(prefix string) error {
prefixPattern := `[a-zA-Z0-9]+_`
matched, err := regexp.MatchString(prefixPattern, prefix)
if err != nil {
return err
}
if !matched {
return fmt.Errorf("invalid prefix %q, the prefix pattern must match the following pattern: %s", prefix, prefixPattern)
}
return nil
}