Add support for field/tag keys to strings processor (influxdata#6129)

plugins/processors/strings/README.md

@@ -14,41 +14,50 @@ Implemented functions are:
 
 Please note that in this implementation these are processed in the order that they appear above.
 
-Specify the `measurement`, `tag` or `field` that you want processed in each section and optionally a `dest` if you want the result stored in a new tag or field. You can specify lots of transformations on data with a single strings processor.
+Specify the `measurement`, `tag`, `tag_key`, `field`, or `field_key` that you want processed in each section and optionally a `dest` if you want the result stored in a new tag or field. You can specify lots of transformations on data with a single strings processor.
 
-If you'd like to apply the change to every `tag`, `field`, or `measurement`, use the value "*" for each respective field. Note that the `dest` field will be ignored if "*" is used
+If you'd like to apply the change to every `tag`, `tag_key`, `field`, `field_key`, or `measurement`, use the value `"*"` for each respective field. Note that the `dest` field will be ignored if `"*"` is used.
+
+If you'd like to apply multiple processings to the same `tag_key` or `field_key`, note the process order stated above. See [Example 2]() for an example.
 
 ### Configuration:
 
 ```toml
 [[processors.strings]]
-  # [[processors.strings.uppercase]]
-  #   tag = "method"
-
+  ## Convert a field value to lowercase and store in a new field
   # [[processors.strings.lowercase]]
   #   field = "uri_stem"
   #   dest = "uri_stem_normalised"
 
-  ## Convert a tag value to lowercase
+  ## Convert a tag value to uppercase
+  # [[processors.strings.uppercase]]
+  #   tag = "method"
+
+  ## Trim leading and trailing whitespace using the default cutset
   # [[processors.strings.trim]]
   #   field = "message"
 
+  ## Trim leading characters in cutset
   # [[processors.strings.trim_left]]
   #   field = "message"
   #   cutset = "\t"
 
+  ## Trim trailing characters in cutset
   # [[processors.strings.trim_right]]
   #   field = "message"
   #   cutset = "\r\n"
 
+  ## Trim the given prefix from the field
   # [[processors.strings.trim_prefix]]
   #   field = "my_value"
   #   prefix = "my_"
 
+  ## Trim the given suffix from the field
   # [[processors.strings.trim_suffix]]
   #   field = "read_count"
   #   suffix = "_count"
 
+  ## Replace all non-overlapping instances of old with new
   # [[processors.strings.replace]]
   #   measurement = "*"
   #   old = ":"
@@ -79,10 +88,10 @@ the operation and keep the old name.
 ```toml
 [[processors.strings]]
   [[processors.strings.lowercase]]
-    field = "uri-stem"
+    tag = "uri_stem"
 
   [[processors.strings.trim_prefix]]
-    field = "uri_stem"
+    tag = "uri_stem"
     prefix = "/api/"
 
   [[processors.strings.uppercase]]
@@ -92,10 +101,33 @@ the operation and keep the old name.
 
 **Input**
 ```
-iis_log,method=get,uri_stem=/API/HealthCheck cs-host="MIXEDCASE_host",referrer="-",ident="-",http_version=1.1,agent="UserAgent",resp_bytes=270i 1519652321000000000
+iis_log,method=get,uri_stem=/API/HealthCheck cs-host="MIXEDCASE_host",http_version=1.1 1519652321000000000
+```
+
+**Output**
+```
+iis_log,method=get,uri_stem=healthcheck cs-host="MIXEDCASE_host",http_version=1.1,cs-host_normalised="MIXEDCASE_HOST" 1519652321000000000
+```
+
+### Example 2
+**Config**
+```toml
+[[processors.strings]]
+  [[processors.strings.lowercase]]
+    tag_key = "URI-Stem"
+
+  [[processors.strings.replace]]
+    tag_key = "uri-stem"
+    old = "-"
+    new = "_"
+```
+
+**Input**
+```
+iis_log,URI-Stem=/API/HealthCheck http_version=1.1 1519652321000000000
 ```
 
 **Output**
 ```
-iis_log,method=get,uri_stem=healthcheck cs-host="MIXEDCASE_host",cs-host_normalised="MIXEDCASE_HOST",referrer="-",ident="-",http_version=1.1,agent="UserAgent",resp_bytes=270i 1519652321000000000
+iis_log,uri_stem=/API/HealthCheck http_version=1.1 1519652321000000000
 ```

plugins/processors/strings/strings.go

@@ -26,7 +26,9 @@ type ConvertFunc func(s string) string
 
 type converter struct {
 	Field       string
+	FieldKey    string
 	Tag         string
+	TagKey      string
 	Measurement string
 	Dest        string
 	Cutset      string
@@ -109,6 +111,27 @@ func (c *converter) convertTag(metric telegraf.Metric) {
 	}
 }
 
+func (c *converter) convertTagKey(metric telegraf.Metric) {
+	var tags map[string]string
+	if c.TagKey == "*" {
+		tags = metric.Tags()
+	} else {
+		tags = make(map[string]string)
+		tv, ok := metric.GetTag(c.TagKey)
+		if !ok {
+			return
+		}
+		tags[c.TagKey] = tv
+	}
+
+	for key, value := range tags {
+		if k := c.fn(key); k != "" {
+			metric.RemoveTag(key)
+			metric.AddTag(k, value)
+		}
+	}
+}
+
 func (c *converter) convertField(metric telegraf.Metric) {
 	var fields map[string]interface{}
 	if c.Field == "*" {
@@ -133,6 +156,27 @@ func (c *converter) convertField(metric telegraf.Metric) {
 	}
 }
 
+func (c *converter) convertFieldKey(metric telegraf.Metric) {
+	var fields map[string]interface{}
+	if c.FieldKey == "*" {
+		fields = metric.Fields()
+	} else {
+		fields = make(map[string]interface{})
+		fv, ok := metric.GetField(c.FieldKey)
+		if !ok {
+			return
+		}
+		fields[c.FieldKey] = fv
+	}
+
+	for key, value := range fields {
+		if k := c.fn(key); k != "" {
+			metric.RemoveField(key)
+			metric.AddField(k, value)
+		}
+	}
+}
+
 func (c *converter) convertMeasurement(metric telegraf.Metric) {
 	if metric.Name() != c.Measurement && c.Measurement != "*" {
 		return
@@ -146,10 +190,18 @@ func (c *converter) convert(metric telegraf.Metric) {
 		c.convertField(metric)
 	}
 
+	if c.FieldKey != "" {
+		c.convertFieldKey(metric)
+	}
+
 	if c.Tag != "" {
 		c.convertTag(metric)
 	}
 
+	if c.TagKey != "" {
+		c.convertTagKey(metric)
+	}
+
 	if c.Measurement != "" {
 		c.convertMeasurement(metric)
 	}