Add result related tags and fields to http_response (#3814)

plugins/inputs/http_response/README.md

@@ -44,18 +44,38 @@ This input plugin will test HTTP/HTTPS connections.
 ### Measurements & Fields:
 
 - http_response
-    - response_time (float, seconds)
-    - http_response_code (int) #The code received
-	- result_type (string) # success, timeout, response_string_mismatch, connection_failed
+    - response_time (float, seconds) # Not set if target is unreachable for any reason
+    - http_response_code (int) # The HTTP code received
+	- result_type (string) # Legacy field mantained for backwards compatibility
+    - result_code (int) # Details [here](#result-tag-and-result_code-field)
+
 
 ### Tags:
 
 - All measurements have the following tags:
-    - server
-    - method
+    - server # Server URL used
+    - method # HTTP method used (GET, POST, PUT, etc)
+    - status_code # String with the HTTP status code
+    - result # Details [here](#result-tag-and-result_code-field)
+
+### Result tag and Result_code field
+Upon finishing polling the target server, the plugin registers the result of the operation in the `result` tag, and adds a numeric field called `result_code` corresponding with that tag value.
+
+This tag is used to expose network and plugin errors. HTTP errors are considered a sucessful connection by the plugin.
+
+|Tag value                |Corresponding field value|Description|
+--------------------------|-------------------------|-----------|
+|success                  | 0                       |The HTTP request completed, even if the HTTP code represents an error|
+|response_string_mismatch | 1                       |The option `response_string_match` was used, and the body of the response didn't match the regex|
+|body_read_error          | 2                       |The option `response_string_match` was used, but the plugin wans't able to read the body of the response. Responses with empty bodies (like 3xx, HEAD, etc) will trigger this error|
+|connection_failed        | 3                       |Catch all for any network error not specifically handled by the plugin|
+|timeout                  | 4                       |The plugin timed out while awaiting the HTTP connection to complete|
+|dns_error                | 5                       |There was a DNS error while attempting to connect to the host|
+
+NOTE: The error codes are derived from the error object returned by the `net/http` Go library, so the accuracy of the errors depends on the handling of error states by the `net/http` Go library. **If a more detailed error report is required use the `log_network_errors` setting.**
 
 ### Example Output:
 
 ```
-http_response,method=GET,server=http://www.github.com http_response_code=200i,response_time=6.223266528 1459419354977857955
+http_response,method=GET,server=http://www.github.com,status_code="200",result="success" http_response_code=200i,response_time=6.223266528,result_type="sucess",result_code=0i 1459419354977857955
 ```

plugins/inputs/http_response/http_response.go

@@ -2,13 +2,15 @@ package http_response
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"io/ioutil"
 	"log"
 	"net"
 	"net/http"
 	"net/url"
 	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
@@ -133,18 +135,62 @@ func (h *HTTPResponse) createHttpClient() (*http.Client, error) {
 	return client, nil
 }
 
+func setResult(result_string string, fields map[string]interface{}, tags map[string]string) {
+	result_codes := map[string]int{
+		"success":                  0,
+		"response_string_mismatch": 1,
+		"body_read_error":          2,
+		"connection_failed":        3,
+		"timeout":                  4,
+		"dns_error":                5,
+	}
+
+	tags["result"] = result_string
+	fields["result_type"] = result_string
+	fields["result_code"] = result_codes[result_string]
+}
+
+func setError(err error, fields map[string]interface{}, tags map[string]string) error {
+	if timeoutError, ok := err.(net.Error); ok && timeoutError.Timeout() {
+		setResult("timeout", fields, tags)
+		return timeoutError
+	}
+
+	urlErr, isUrlErr := err.(*url.Error)
+	if !isUrlErr {
+		return nil
+	}
+
+	opErr, isNetErr := (urlErr.Err).(*net.OpError)
+	if isNetErr {
+		switch e := (opErr.Err).(type) {
+		case (*net.DNSError):
+			setResult("dns_error", fields, tags)
+			return e
+		case (*net.ParseError):
+			// Parse error has to do with parsing of IP addresses, so we
+			// group it with address errors
+			setResult("address_error", fields, tags)
+			return e
+		}
+	}
+
+	return nil
+}
+
 // HTTPGather gathers all fields and returns any errors it encounters
-func (h *HTTPResponse) httpGather() (map[string]interface{}, error) {
-	// Prepare fields
+func (h *HTTPResponse) httpGather() (map[string]interface{}, map[string]string, error) {
+	// Prepare fields and tags
 	fields := make(map[string]interface{})
+	tags := map[string]string{"server": h.Address, "method": h.Method}
 
 	var body io.Reader
 	if h.Body != "" {
 		body = strings.NewReader(h.Body)
 	}
 	request, err := http.NewRequest(h.Method, h.Address, body)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 
 	for key, val := range h.Headers {
@@ -157,68 +203,87 @@ func (h *HTTPResponse) httpGather() (map[string]interface{}, error) {
 	// Start Timer
 	start := time.Now()
 	resp, err := h.client.Do(request)
+	response_time := time.Since(start).Seconds()
 
+	// If an error in returned, it means we are dealing with a network error, as
+	// HTTP error codes do not generate errors in the net/http library
 	if err != nil {
-		if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
-			fields["result_type"] = "timeout"
-			return fields, nil
-		}
-		fields["result_type"] = "connection_failed"
-		if h.FollowRedirects {
-			return fields, nil
+		// Log error
+		log.Printf("D! Network error while polling %s: %s", h.Address, err.Error())
+
+		// Get error details
+		netErr := setError(err, fields, tags)
+
+		// If recognize the returnded error, get out
+		if netErr != nil {
+			return fields, tags, nil
 		}
-		if urlError, ok := err.(*url.Error); ok &&
-			urlError.Err == ErrRedirectAttempted {
+
+		// Any error not recognized by `set_error` is considered a "connection_failed"
+		setResult("connection_failed", fields, tags)
+
+		// If the error is a redirect we continue processing and log the HTTP code
+		urlError, isUrlError := err.(*url.Error)
+		if !h.FollowRedirects && isUrlError && urlError.Err == ErrRedirectAttempted {
 			err = nil
 		} else {
-			return fields, nil
+			// If the error isn't a timeout or a redirect stop
+			// processing the request
+			return fields, tags, nil
 		}
 	}
+
+	if _, ok := fields["response_time"]; !ok {
+		fields["response_time"] = response_time
+	}
+
+	// This function closes the response body, as
+	// required by the net/http library
 	defer func() {
 		io.Copy(ioutil.Discard, resp.Body)
 		resp.Body.Close()
 	}()
 
-	fields["response_time"] = time.Since(start).Seconds()
+	// Set log the HTTP response code
+	tags["status_code"] = strconv.Itoa(resp.StatusCode)
 	fields["http_response_code"] = resp.StatusCode
 
 	// Check the response for a regex match.
 	if h.ResponseStringMatch != "" {
 
-		// Compile once and reuse
-		if h.compiledStringMatch == nil {
-			h.compiledStringMatch = regexp.MustCompile(h.ResponseStringMatch)
-			if err != nil {
-				log.Printf("E! Failed to compile regular expression %s : %s", h.ResponseStringMatch, err)
-				fields["result_type"] = "response_string_mismatch"
-				return fields, nil
-			}
-		}
-
 		bodyBytes, err := ioutil.ReadAll(resp.Body)
 		if err != nil {
-			log.Printf("E! Failed to read body of HTTP Response : %s", err)
-			fields["result_type"] = "response_string_mismatch"
+			log.Printf("D! Failed to read body of HTTP Response : %s", err)
+			setResult("body_read_error", fields, tags)
 			fields["response_string_match"] = 0
-			return fields, nil
+			return fields, tags, nil
 		}
 
 		if h.compiledStringMatch.Match(bodyBytes) {
-			fields["result_type"] = "success"
+			setResult("success", fields, tags)
 			fields["response_string_match"] = 1
 		} else {
-			fields["result_type"] = "response_string_mismatch"
+			setResult("response_string_mismatch", fields, tags)
 			fields["response_string_match"] = 0
 		}
 	} else {
-		fields["result_type"] = "success"
+		setResult("success", fields, tags)
 	}
 
-	return fields, nil
+	return fields, tags, nil
 }
 
 // Gather gets all metric fields and tags and returns any errors it encounters
 func (h *HTTPResponse) Gather(acc telegraf.Accumulator) error {
+	// Compile the body regex if it exist
+	if h.compiledStringMatch == nil {
+		var err error
+		h.compiledStringMatch, err = regexp.Compile(h.ResponseStringMatch)
+		if err != nil {
+			return fmt.Errorf("Failed to compile regular expression %s : %s", h.ResponseStringMatch, err)
+		}
+	}
+
 	// Set default values
 	if h.ResponseTimeout.Duration < time.Second {
 		h.ResponseTimeout.Duration = time.Second * 5
@@ -237,9 +302,10 @@ func (h *HTTPResponse) Gather(acc telegraf.Accumulator) error {
 	if addr.Scheme != "http" && addr.Scheme != "https" {
 		return errors.New("Only http and https are supported")
 	}
+
 	// Prepare data
-	tags := map[string]string{"server": h.Address, "method": h.Method}
 	var fields map[string]interface{}
+	var tags map[string]string
 
 	if h.client == nil {
 		client, err := h.createHttpClient()
@@ -250,10 +316,11 @@ func (h *HTTPResponse) Gather(acc telegraf.Accumulator) error {
 	}
 
 	// Gather data
-	fields, err = h.httpGather()
+	fields, tags, err = h.httpGather()
 	if err != nil {
 		return err
 	}
+
 	// Add metrics
 	acc.AddFields("http_response", fields, tags)
 	return nil