fix(output.datadog): log response in case of non 2XX response from API (#12201)

plugins/outputs/datadog/datadog.go

@@ -6,6 +6,7 @@ import (
 	_ "embed"
 	"encoding/json"
 	"fmt"
+	"io"
 	"math"
 	"net/http"
 	"net/url"
@@ -168,7 +169,9 @@ func (d *Datadog) Write(metrics []telegraf.Metric) error {
 	defer resp.Body.Close()
 
 	if resp.StatusCode < 200 || resp.StatusCode > 209 {
-		return fmt.Errorf("received bad status code, %d", resp.StatusCode)
+		// err can be ignored
+		body, _ := io.ReadAll(resp.Body)
+		return fmt.Errorf("received bad status code, %d: %s", resp.StatusCode, string(body))
 	}
 
 	return nil

plugins/outputs/datadog/datadog_test.go

@@ -24,6 +24,7 @@ var (
 func NewDatadog(url string) *Datadog {
 	return &Datadog{
 		URL: url,
+		Log: testutil.Logger{},
 	}
 }
 
@@ -67,14 +68,10 @@ func TestCompressionOverride(t *testing.T) {
 }
 
 func TestBadStatusCode(t *testing.T) {
+	errorString := `{"errors": ["Something bad happened to the server.", "Your query made the server very sad."]}`
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusInternalServerError)
-		//nolint:errcheck,revive // Ignore the returned error as the test will fail anyway
-		json.NewEncoder(w).Encode(`{ 'errors': [
-    	'Something bad happened to the server.',
-    	'Your query made the server very sad.'
-  		]
-		}`)
+		fmt.Fprint(w, errorString)
 	}))
 	defer ts.Close()
 
@@ -86,7 +83,7 @@ func TestBadStatusCode(t *testing.T) {
 	if err == nil {
 		t.Errorf("error expected but none returned")
 	} else {
-		require.EqualError(t, fmt.Errorf("received bad status code, 500"), err.Error())
+		require.EqualError(t, err, fmt.Sprintf("received bad status code, %v: %s", http.StatusInternalServerError, errorString))
 	}
 }