Don't report 0ms on timeout in dns_query (#4118)

plugins/inputs/dns_query/README.md

@@ -3,9 +3,8 @@
 The DNS plugin gathers dns query times in miliseconds - like [Dig](https://en.wikipedia.org/wiki/Dig_\(command\))
 
 ### Configuration:
-
-```
-# Sample Config:
+```toml
+# Query given DNS server and gives statistics
 [[inputs.dns_query]]
   ## servers to query
   servers = ["8.8.8.8"]
@@ -27,29 +26,20 @@ The DNS plugin gathers dns query times in miliseconds - like [Dig](https://en.wi
   # timeout = 2
 ```
 
-For querying more than one record type make:
+### Metrics:
+
+- dns_query
+  - tags:
+    - server
+    - domain
+    - record_type
+    - result
+  - fields:
+    - query_time_ms (float)
+    - result_code (int, success = 0, timeout = 1, error = 2)
+
+### Example Output:
 
 ```
-[[inputs.dns_query]]
-  domains = ["mjasion.pl"]
-  servers = ["8.8.8.8", "8.8.4.4"]
-  record_type = "A"
-
-[[inputs.dns_query]]
-  domains = ["mjasion.pl"]
-  servers = ["8.8.8.8", "8.8.4.4"]
-  record_type = "MX"
-```
-
-### Tags:
-
-- server
-- domain
-- record_type
-
-### Example output:
-
-```
-telegraf --input-filter dns_query --test
-> dns_query,domain=mjasion.pl,record_type=A,server=8.8.8.8 query_time_ms=67.189842 1456082743585760680
+dns_query,domain=mjasion.pl,record_type=A,server=8.8.8.8 query_time_ms=67.189842 1456082743585760680
 ```

plugins/inputs/dns_query/dns_query.go

@@ -13,6 +13,14 @@ import (
 	"github.com/influxdata/telegraf/plugins/inputs"
 )
 
+type ResultType uint64
+
+const (
+	Success ResultType = 0
+	Timeout            = 1
+	Error              = 2
+)
+
 type DnsQuery struct {
 	// Domains or subdomains to query
 	Domains []string
@@ -66,15 +74,24 @@ func (d *DnsQuery) Gather(acc telegraf.Accumulator) error {
 
 	for _, domain := range d.Domains {
 		for _, server := range d.Servers {
-			dnsQueryTime, err := d.getDnsQueryTime(domain, server)
-			acc.AddError(err)
+			fields := make(map[string]interface{}, 2)
 			tags := map[string]string{
 				"server":      server,
 				"domain":      domain,
 				"record_type": d.RecordType,
 			}
 
-			fields := map[string]interface{}{"query_time_ms": dnsQueryTime}
+			dnsQueryTime, err := d.getDnsQueryTime(domain, server)
+			if err == nil {
+				setResult(Success, fields, tags)
+				fields["query_time_ms"] = dnsQueryTime
+			} else if opErr, ok := err.(*net.OpError); ok && opErr.Timeout() {
+				setResult(Timeout, fields, tags)
+			} else if err != nil {
+				setResult(Error, fields, tags)
+				acc.AddError(err)
+			}
+
 			acc.AddFields("dns_query", fields, tags)
 		}
 	}
@@ -165,6 +182,21 @@ func (d *DnsQuery) parseRecordType() (uint16, error) {
 	return recordType, error
 }
 
+func setResult(result ResultType, fields map[string]interface{}, tags map[string]string) {
+	var tag string
+	switch result {
+	case Success:
+		tag = "success"
+	case Timeout:
+		tag = "timeout"
+	case Error:
+		tag = "error"
+	}
+
+	tags["result"] = tag
+	fields["result_code"] = uint64(result)
+}
+
 func init() {
 	inputs.Add("dns_query", func() telegraf.Input {
 		return &DnsQuery{}