Gather elasticsearch nodes in goroutines, handle errors

fixes #464

plugins/inputs/elasticsearch/elasticsearch.go

@@ -2,8 +2,11 @@ package elasticsearch
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
+	"strings"
+	"sync"
 	"time"
 
 	"github.com/influxdata/telegraf/internal"
@@ -93,21 +96,41 @@ func (e *Elasticsearch) Description() string {
 // Gather reads the stats from Elasticsearch and writes it to the
 // Accumulator.
 func (e *Elasticsearch) Gather(acc inputs.Accumulator) error {
+	errChan := make(chan error, len(e.Servers))
+	var wg sync.WaitGroup
+	wg.Add(len(e.Servers))
+
 	for _, serv := range e.Servers {
-		var url string
-		if e.Local {
-			url = serv + statsPathLocal
-		} else {
-			url = serv + statsPath
-		}
-		if err := e.gatherNodeStats(url, acc); err != nil {
-			return err
-		}
-		if e.ClusterHealth {
-			e.gatherClusterStats(fmt.Sprintf("%s/_cluster/health?level=indices", serv), acc)
-		}
+		go func(s string, acc inputs.Accumulator) {
+			defer wg.Done()
+			var url string
+			if e.Local {
+				url = s + statsPathLocal
+			} else {
+				url = s + statsPath
+			}
+			if err := e.gatherNodeStats(url, acc); err != nil {
+				errChan <- err
+				return
+			}
+			if e.ClusterHealth {
+				e.gatherClusterStats(fmt.Sprintf("%s/_cluster/health?level=indices", s), acc)
+			}
+		}(serv, acc)
 	}
-	return nil
+
+	wg.Wait()
+	close(errChan)
+	// Get all errors and return them as one giant error
+	errStrings := []string{}
+	for err := range errChan {
+		errStrings = append(errStrings, err.Error())
+	}
+
+	if len(errStrings) == 0 {
+		return nil
+	}
+	return errors.New(strings.Join(errStrings, "\n"))
 }
 
 func (e *Elasticsearch) gatherNodeStats(url string, acc inputs.Accumulator) error {