show the original error message returned from the VictoriaLogs backend

fix tests

update changelog description

update changelog description

Author: dmitryk-dk

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## tip
 
+* BUGFIX: show the original error message returned from the VictoriaLogs backend on status code 400. It should help to troubleshoot problems with query or syntax. See [this pull request](https://github.com/VictoriaMetrics/victorialogs-datasource/pull/287).
+
 ## v0.16.2
 
 * BUGFIX: properly close io.ReadCloser to avoid memory leak. See [this pull request](https://github.com/VictoriaMetrics/victorialogs-datasource/pull/280).

pkg/plugin/datasource.go

@@ -298,10 +298,14 @@ func (d *Datasource) datasourceQuery(ctx context.Context, q *Query, isStream boo
 	}
 
 	if resp.StatusCode != http.StatusOK {
-		if resp.StatusCode == http.StatusUnprocessableEntity {
+		switch resp.StatusCode {
+		case http.StatusUnprocessableEntity:
 			return nil, parseErrorResponse(resp.Body)
+		case http.StatusBadRequest:
+			return nil, parseStringResponseError(resp.Body)
+		default:
+			return nil, fmt.Errorf("failed to make http request: %d", resp.StatusCode)
 		}
-		return nil, fmt.Errorf("got unexpected response status code: %d", resp.StatusCode)
 	}
 
 	return resp.Body, nil

pkg/plugin/datasource_test.go

@@ -134,7 +134,7 @@ func TestDatasourceQueryRequest(t *testing.T) {
 		}
 	}
 
-	expErr(ctx, "got unexpected response status code: 500")                                                                                                                    // 0
+	expErr(ctx, "failed to make http request: 500")                                                                                                                            // 0
 	expErr(ctx, "error get object from decoded response: value doesn't contain object; it contains number")                                                                    // 1
 	expErr(ctx, "error parse time from _time field: cannot parse acdf: cannot parse duration \"acdf\"")                                                                        // 2
 	expErr(ctx, "error decode response: cannot parse JSON: cannot parse number: unexpected char: \"c\"; unparsed tail: \"cannot parse query []: missing query; context: []\"") // 3
@@ -545,7 +545,7 @@ func TestDatasourceStreamQueryRequest(t *testing.T) {
 		}
 	}
 
-	expErr(ctx, "got unexpected response status code: 500")                                                                                                                    // 0
+	expErr(ctx, "failed to make http request: 500")                                                                                                                            // 0
 	expErr(ctx, "error get object from decoded response: value doesn't contain object; it contains number")                                                                    // 1
 	expErr(ctx, "error parse time from _time field: cannot parse acdf: cannot parse duration \"acdf\"")                                                                        // 2
 	expErr(ctx, "error decode response: cannot parse JSON: cannot parse number: unexpected char: \"c\"; unparsed tail: \"cannot parse query []: missing query; context: []\"") // 3

pkg/plugin/response.go

@@ -316,6 +316,18 @@ func parseErrorResponse(reader io.Reader) error {
 	return nil
 }
 
+// parseStringResponseError reads data from the reader and returns error
+func parseStringResponseError(reader io.Reader) error {
+	d, err := io.ReadAll(reader)
+	if err != nil {
+		return fmt.Errorf("failed to read body response: %w", err)
+	}
+	if len(d) == 0 {
+		return fmt.Errorf("got empty response from the datasource")
+	}
+	return fmt.Errorf("error from datasource: %s", string(d))
+}
+
 // labelsToJSON converts labels to json representation
 // data.Labels when converted to JSON keep the fields sorted
 func labelsToJSON(labels data.Labels) (json.RawMessage, error) {