Add ability to set measurement from matched text in grok parser (#4433)

plugins/inputs/file/README.md

@@ -14,7 +14,7 @@ use the [tail input plugin](/plugins/inputs/tail) instead.
   ## ** as a "super asterisk". ie:
   ##   /var/log/**.log     -> recursively find all .log files in /var/log
   ##   /var/log/*/*.log    -> find all .log files with a parent dir in /var/log
-  ##   /var/log/apache.log -> only tail the apache log file
+  ##   /var/log/apache.log -> only read the apache log file
   files = ["/var/log/apache/access.log"]
 
   ## Data format to consume.

plugins/inputs/file/dev/docker-compose.yml

@@ -6,7 +6,7 @@ services:
       volumes:
         - ./telegraf.conf:/telegraf.conf
         - ../../../../telegraf:/telegraf
-        - ./json_a.log:/var/log/test.log
+        - ./dev/json_a.log:/var/log/test.log
       entrypoint:
         - /telegraf
         - --config

plugins/inputs/file/dev/json_a.log

@@ -1,14 +0,0 @@
-{
-"parent": {
-	"child": 3.0,
-	"ignored_child": "hi"
-},
-"ignored_null": null,
-"integer": 4,
-"list": [3, 4],
-"ignored_parent": {
-	"another_ignored_null": null,
-	"ignored_string": "hello, world!"
-},
-"another_list": [4]
-}

plugins/inputs/file/file.go

@@ -11,9 +11,8 @@ import (
 )
 
 type File struct {
-	Files         []string `toml:"files"`
-	FromBeginning bool
-	parser        parsers.Parser
+	Files  []string `toml:"files"`
+	parser parsers.Parser
 
 	filenames []string
 }
@@ -24,7 +23,7 @@ const sampleConfig = `
   ## ** as a "super asterisk". ie:
   ##   /var/log/**.log     -> recursively find all .log files in /var/log
   ##   /var/log/*/*.log    -> find all .log files with a parent dir in /var/log
-  ##   /var/log/apache.log -> only tail the apache log file
+  ##   /var/log/apache.log -> only read the apache log file
   files = ["/var/log/apache/access.log"]
 
   ## The dataformat to be read from files
@@ -40,7 +39,7 @@ func (f *File) SampleConfig() string {
 }
 
 func (f *File) Description() string {
-	return "reload and gather from file[s] on telegraf's interval"
+	return "Reload and gather from file[s] on telegraf's interval."
 }
 
 func (f *File) Gather(acc telegraf.Accumulator) error {

plugins/inputs/file/file_test.go

@@ -14,26 +14,26 @@ import (
 func TestRefreshFilePaths(t *testing.T) {
 	wd, err := os.Getwd()
 	r := File{
-		Files: []string{filepath.Join(wd, "testfiles/**.log")},
+		Files: []string{filepath.Join(wd, "dev/testfiles/**.log")},
 	}
 
 	err = r.refreshFilePaths()
 	require.NoError(t, err)
-	assert.Equal(t, len(r.filenames), 2)
+	assert.Equal(t, 2, len(r.filenames))
 }
 func TestJSONParserCompile(t *testing.T) {
 	var acc testutil.Accumulator
 	wd, _ := os.Getwd()
 	r := File{
-		Files: []string{filepath.Join(wd, "testfiles/json_a.log")},
+		Files: []string{filepath.Join(wd, "dev/testfiles/json_a.log")},
 	}
 	parserConfig := parsers.Config{
 		DataFormat: "json",
 		TagKeys:    []string{"parent_ignored_child"},
 	}
 	nParser, err := parsers.NewParser(&parserConfig)
-	r.parser = nParser
 	assert.NoError(t, err)
+	r.parser = nParser
 
 	r.Gather(&acc)
 	assert.Equal(t, map[string]string{"parent_ignored_child": "hi"}, acc.Metrics[0].Tags)
@@ -44,7 +44,7 @@ func TestGrokParser(t *testing.T) {
 	wd, _ := os.Getwd()
 	var acc testutil.Accumulator
 	r := File{
-		Files: []string{filepath.Join(wd, "testfiles/grok_a.log")},
+		Files: []string{filepath.Join(wd, "dev/testfiles/grok_a.log")},
 	}
 
 	parserConfig := parsers.Config{
@@ -57,5 +57,5 @@ func TestGrokParser(t *testing.T) {
 	assert.NoError(t, err)
 
 	err = r.Gather(&acc)
-	assert.Equal(t, 2, len(acc.Metrics))
+	assert.Equal(t, len(acc.Metrics), 2)
 }