Continue checking cert from other sources if error occurs (#5381)

plugins/inputs/x509_cert/x509_cert.go

@@ -166,7 +166,7 @@ func (c *X509Cert) Gather(acc telegraf.Accumulator) error {
 	for _, location := range c.Sources {
 		certs, err := c.getCert(location, c.Timeout.Duration*time.Second)
 		if err != nil {
-			return fmt.Errorf("cannot get SSL cert '%s': %s", location, err.Error())
+			acc.AddError(fmt.Errorf("cannot get SSL cert '%s': %s", location, err.Error()))
 		}
 
 		for _, cert := range certs {

plugins/inputs/x509_cert/x509_cert_test.go

@@ -4,13 +4,14 @@ import (
 	"crypto/tls"
 	"encoding/base64"
 	"fmt"
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 	"io/ioutil"
 	"os"
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/testutil"
@@ -115,7 +116,7 @@ func TestGatherRemote(t *testing.T) {
 
 			acc := testutil.Accumulator{}
 			err = sc.Gather(&acc)
-			if err != nil {
+			if len(acc.Errors) > 0 {
 				testErr = true
 			}
 
@@ -173,7 +174,7 @@ func TestGatherLocal(t *testing.T) {
 
 			acc := testutil.Accumulator{}
 			err = sc.Gather(&acc)
-			if err != nil {
+			if len(acc.Errors) > 0 {
 				error = true
 			}