Add regex processor plugin (#3839)

plugins/processors/all/all.go

@@ -3,5 +3,6 @@ package all
 import (
 	_ "github.com/influxdata/telegraf/plugins/processors/override"
 	_ "github.com/influxdata/telegraf/plugins/processors/printer"
+	_ "github.com/influxdata/telegraf/plugins/processors/regex"
 	_ "github.com/influxdata/telegraf/plugins/processors/topk"
 )

plugins/processors/regex/README.md

@@ -0,0 +1,46 @@
+# Regex Processor Plugin
+
+The `regex` plugin transforms tag and field values with regex pattern. If `result_key` parameter is present, it can produce new tags and fields from existing ones.
+
+### Configuration:
+
+```toml
+[[processors.regex]]
+  namepass = ["nginx_requests"]
+
+  # Tag and field conversions defined in a separate sub-tables
+  [[processors.regex.tags]]
+    ## Tag to change
+    key = "resp_code"
+    ## Regular expression to match on a tag value
+    pattern = "^(\\d)\\d\\d$"
+    ## Pattern for constructing a new value (${1} represents first subgroup)
+    replacement = "${1}xx"
+
+  [[processors.regex.fields]]
+    key = "request"
+    ## All the power of the Go regular expressions available here
+    ## For example, named subgroups
+    pattern = "^/api(?P<method>/[\\w/]+)\\S*"
+    replacement = "${method}"
+    ## If result_key is present, a new field will be created
+    ## instead of changing existing field
+    result_key = "method"
+
+  # Multiple conversions may be applied for one field sequentially
+  # Let's extract one more value
+  [[processors.regex.fields]]
+    key = "request"
+    pattern = ".*category=(\\w+).*"
+    replacement = "${1}"
+    result_key = "search_category"
+```
+
+### Tags:
+
+No tags are applied by this processor.
+
+### Example Output:
+```
+nginx_requests,verb=GET,resp_code=2xx request="/api/search/?category=plugins&q=regex&sort=asc",method="/search/",search_category="plugins",referrer="-",ident="-",http_version=1.1,agent="UserAgent",client_ip="127.0.0.1",auth="-",resp_bytes=270i 1519652321000000000
+```

plugins/processors/regex/regex.go

@@ -0,0 +1,110 @@
+package regex
+
+import (
+	"regexp"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/processors"
+)
+
+type Regex struct {
+	Tags       []converter
+	Fields     []converter
+	regexCache map[string]*regexp.Regexp
+}
+
+type converter struct {
+	Key         string
+	Pattern     string
+	Replacement string
+	ResultKey   string
+}
+
+const sampleConfig = `
+  ## Tag and field conversions defined in a separate sub-tables
+  # [[processors.regex.tags]]
+  #   ## Tag to change
+  #   key = "resp_code"
+  #   ## Regular expression to match on a tag value
+  #   pattern = "^(\\d)\\d\\d$"
+  #   ## Pattern for constructing a new value (${1} represents first subgroup)
+  #   replacement = "${1}xx"
+
+  # [[processors.regex.fields]]
+  #   key = "request"
+  #   ## All the power of the Go regular expressions available here
+  #   ## For example, named subgroups
+  #   pattern = "^/api(?P<method>/[\\w/]+)\\S*" 
+  #   replacement = "${method}"
+  #   ## If result_key is present, a new field will be created
+  #   ## instead of changing existing field
+  #   result_key = "method"
+
+  ## Multiple conversions may be applied for one field sequentially
+  ## Let's extract one more value
+  # [[processors.regex.fields]]
+  #   key = "request"
+  #   pattern = ".*category=(\\w+).*"
+  #   replacement = "${1}"
+  #   result_key = "search_category"
+`
+
+func NewRegex() *Regex {
+	return &Regex{
+		regexCache: make(map[string]*regexp.Regexp),
+	}
+}
+
+func (r *Regex) SampleConfig() string {
+	return sampleConfig
+}
+
+func (r *Regex) Description() string {
+	return "Transforms tag and field values with regex pattern"
+}
+
+func (r *Regex) Apply(in ...telegraf.Metric) []telegraf.Metric {
+	for _, metric := range in {
+		for _, converter := range r.Tags {
+			if value, ok := metric.GetTag(converter.Key); ok {
+				metric.AddTag(r.convert(converter, value))
+			}
+		}
+
+		for _, converter := range r.Fields {
+			if value, ok := metric.GetField(converter.Key); ok {
+				switch value := value.(type) {
+				case string:
+					metric.AddField(r.convert(converter, value))
+				}
+			}
+		}
+	}
+
+	return in
+}
+
+func (r *Regex) convert(c converter, src string) (string, string) {
+	regex, compiled := r.regexCache[c.Pattern]
+	if !compiled {
+		regex = regexp.MustCompile(c.Pattern)
+		r.regexCache[c.Pattern] = regex
+	}
+
+	value := ""
+	if c.ResultKey == "" || regex.MatchString(src) {
+		value = regex.ReplaceAllString(src, c.Replacement)
+	}
+
+	if c.ResultKey != "" {
+		return c.ResultKey, value
+	}
+
+	return c.Key, value
+}
+
+func init() {
+	processors.Add("regex", func() telegraf.Processor {
+		return NewRegex()
+	})
+}