telegraf/internal/templating/engine.go

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package templating
import (
"sort"
"strings"
)
const (
// DefaultSeparator is the default separation character to use when separating template parts.
DefaultSeparator = "."
)
// Engine uses a Matcher to retrieve the appropriate template and applies the template
// to the input string
type Engine struct {
joiner string
matcher *matcher
}
// Apply extracts the template fields from the given line and returns the measurement
// name, tags and field name
func (e *Engine) Apply(line string) (string, map[string]string, string, error) {
return e.matcher.match(line).Apply(line, e.joiner)
}
// NewEngine creates a new templating engine
func NewEngine(joiner string, defaultTemplate *Template, templates []string) (*Engine, error) {
engine := Engine{
joiner: joiner,
matcher: newMatcher(defaultTemplate),
}
templateSpecs := parseTemplateSpecs(templates)
for _, templateSpec := range templateSpecs {
if err := engine.matcher.addSpec(templateSpec); err != nil {
return nil, err
}
}
return &engine, nil
}
func parseTemplateSpecs(templates []string) templateSpecs {
tmplts := templateSpecs{}
for _, pattern := range templates {
tmplt := templateSpec{
separator: DefaultSeparator,
}
// Format is [separator] [filter] <template> [tag1=value1,tag2=value2]
parts := strings.Fields(pattern)
partsLength := len(parts)
if partsLength < 1 {
// ignore
continue
}
if partsLength == 1 {
tmplt.template = pattern
} else if partsLength == 4 {
tmplt.separator = parts[0]
tmplt.filter = parts[1]
tmplt.template = parts[2]
tmplt.tagstring = parts[3]
} else {
hasTagstring := strings.Contains(parts[partsLength-1], "=")
if hasTagstring {
tmplt.tagstring = parts[partsLength-1]
tmplt.template = parts[partsLength-2]
if partsLength == 3 {
tmplt.filter = parts[0]
}
} else {
tmplt.template = parts[partsLength-1]
if partsLength == 2 {
tmplt.filter = parts[0]
} else { // length == 3
tmplt.separator = parts[0]
tmplt.filter = parts[1]
}
}
}
tmplts = append(tmplts, tmplt)
}
sort.Sort(tmplts)
return tmplts
}