add "field_tags" to json parser config

docs/DATA_FORMATS_INPUT.md

@@ -104,9 +104,10 @@ but can be overridden using the `name_override` config option.
 
 #### JSON Configuration:
 
-The JSON data format supports specifying "tag keys". If specified, keys
+The JSON data format supports specifying "tag keys" and "field keys". If specified, keys
-will be searched for in the root-level of the JSON blob. If the key(s) exist,
+will be searched for in the root-level and any nested lists of the JSON blob. If the key(s) exist,
-they will be applied as tags to the Telegraf metrics.
+they will be applied as tags or fields to the Telegraf metrics.  If "field_keys" is not specified,
+all int and float values will be set as fields by default.
 
 For example, if you had this configuration:
 
@@ -173,6 +174,7 @@ For example, if the following configuration:
     "my_tag_1",
     "my_tag_2"
   ]
+  field_keys = ["b_c"]
 ```
 
 with this JSON output from a command:
@@ -198,11 +200,11 @@ with this JSON output from a command:
 ]
 ```
 
-Your Telegraf metrics would get tagged with "my_tag_1" and "my_tag_2"
+Your Telegraf metrics would get tagged with "my_tag_1" and "my_tag_2" and fielded with "b_c"
 
 ```
-exec_mycollector,my_tag_1=foo,my_tag_2=baz a=5,b_c=6
+exec_mycollector,my_tag_1=foo,my_tag_2=baz b_c=6
-exec_mycollector,my_tag_1=bar,my_tag_2=baz a=7,b_c=8
+exec_mycollector,my_tag_1=bar,my_tag_2=baz b_c=8
 ```
 
 # Value:

internal/config/config.go

@@ -1261,6 +1261,18 @@ func buildParser(name string, tbl *ast.Table) (parsers.Parser, error) {
 		}
 	}
 
+	if node, ok := tbl.Fields["field_keys"]; ok {
+		if kv, ok := node.(*ast.KeyValue); ok {
+			if ary, ok := kv.Value.(*ast.Array); ok {
+				for _, elem := range ary.Value {
+					if str, ok := elem.(*ast.String); ok {
+						c.FieldKeys = append(c.FieldKeys, str.Value)
+					}
+				}
+			}
+		}
+	}
+
 	if node, ok := tbl.Fields["data_type"]; ok {
 		if kv, ok := node.(*ast.KeyValue); ok {
 			if str, ok := kv.Value.(*ast.String); ok {
@@ -1344,6 +1356,7 @@ func buildParser(name string, tbl *ast.Table) (parsers.Parser, error) {
 	delete(tbl.Fields, "separator")
 	delete(tbl.Fields, "templates")
 	delete(tbl.Fields, "tag_keys")
+	delete(tbl.Fields, "field_keys")
 	delete(tbl.Fields, "data_type")
 	delete(tbl.Fields, "collectd_auth_file")
 	delete(tbl.Fields, "collectd_security_level")

internal/config/config_test.go

@@ -143,7 +143,7 @@ func TestConfig_LoadDirectory(t *testing.T) {
 		"Testdata did not produce correct memcached metadata.")
 
 	ex := inputs.Inputs["exec"]().(*exec.Exec)
-	p, err := parsers.NewJSONParser("exec", nil, nil)
+	p, err := parsers.NewJSONParser("exec", nil, nil, nil)
 	assert.NoError(t, err)
 	ex.SetParser(p)
 	ex.Command = "/usr/bin/myothercollector --foo=bar"

plugins/parsers/json/parser.go

@@ -20,6 +20,7 @@ var (
 type JSONParser struct {
 	MetricName  string
 	TagKeys     []string
+	FieldKeys   []string
 	DefaultTags map[string]string
 }
 
@@ -86,6 +87,17 @@ func (p *JSONParser) switchFieldToTag(tags map[string]string, fields map[string]
 		}
 	}
 
+	//if field_keys is specified, only those values should be reported as fields
+	if len(p.FieldKeys) > 0 {
+		nFields := make(map[string]interface{})
+		for _, name := range p.FieldKeys {
+			if fields[name] != nil {
+				nFields[name] = fields[name]
+			}
+		}
+		return tags, nFields
+	}
+
 	//remove any additional string/bool values from fields
 	for k := range fields {
 		switch fields[k].(type) {

plugins/parsers/json/parser_test.go

@@ -454,13 +454,18 @@ func TestJSONParseNestedArray(t *testing.T) {
 		"avg_find_time": 4,
 		"tester": "work",
 		"tester2": "don't want this",
-	"tester3": 7.93
+		"tester3": {
+			"hello":"sup",
+			"fun":"money",
+			"break":9
+		}
 	}
 	}`
 
 	parser := JSONParser{
 		MetricName: "json_test",
-		TagKeys:    []string{"total_devices", "total_threads", "shares_tester", "shares_tester3"},
+		TagKeys:    []string{"total_devices", "total_threads", "shares_tester3_fun"},
+		FieldKeys:  []string{"shares_tester", "shares_tester3_break"},
 	}
 
 	metrics, err := parser.Parse([]byte(testString))

plugins/parsers/registry.go

@@ -56,6 +56,8 @@ type Config struct {
 
 	// TagKeys only apply to JSON data
 	TagKeys []string
+	// FieldKeys only apply to JSON
+	FieldKeys []string
 	// MetricName applies to JSON & value. This will be the name of the measurement.
 	MetricName string
 
@@ -96,7 +98,7 @@ func NewParser(config *Config) (Parser, error) {
 	switch config.DataFormat {
 	case "json":
 		parser, err = NewJSONParser(config.MetricName,
-			config.TagKeys, config.DefaultTags)
+			config.TagKeys, config.FieldKeys, config.DefaultTags)
 	case "value":
 		parser, err = NewValueParser(config.MetricName,
 			config.DataType, config.DefaultTags)
@@ -129,11 +131,13 @@ func NewParser(config *Config) (Parser, error) {
 func NewJSONParser(
 	metricName string,
 	tagKeys []string,
+	fieldKeys []string,
 	defaultTags map[string]string,
 ) (Parser, error) {
 	parser := &json.JSONParser{
 		MetricName:  metricName,
 		TagKeys:     tagKeys,
+		FieldKeys:   fieldKeys,
 		DefaultTags: defaultTags,
 	}
 	return parser, nil