fix(error): unsupported value: +Inf" error not handled gracefully (#2…

…0276)

* fix(error): unsupported value: +Inf" error not handled gracefully

JSON marshalling errors should be returned properly formatted in JSON
like other errors. This fix formats marshalling errors the same way
influxdb formats other query errors.

Fixes #20249

(cherry picked from commit 2407077)

* chore(changelog): update CHANGELOG.md for PR #20276

CHANGELOG.md

@@ -9,6 +9,7 @@ v1.8.4 [unreleased]
 
 -	[#20101](https://github.com/influxdata/influxdb/pull/20101): fix(write): Successful writes increment write error statistics incorrectly
 -	[#19696](https://github.com/influxdata/influxdb/pull/19697): fix(flux): add durations to Flux logging
+	[#20276](https://github.com/influxdata/influxdb/pull/20276): fix(error): unsupported value: +Inf" error not handled gracefully
 
 v1.8.3 [2020-09-30]
 -------------------

services/httpd/response_writer.go

@@ -3,6 +3,7 @@ package httpd
 import (
 	"encoding/csv"
 	"encoding/json"
+	"errors"
 	"io"
 	"net/http"
 	"strconv"
@@ -97,9 +98,13 @@ func (w *bytesCountWriter) Write(data []byte) (int, error) {
 
 // WriteResponse writes the response using the formatter.
 func (w *responseWriter) WriteResponse(resp Response) (int, error) {
+	n := 0
 	writer := bytesCountWriter{w: w.ResponseWriter}
 	err := w.formatter.WriteResponse(&writer, resp)
-	return writer.n, err
+	if err != nil {
+		n, _ = WriteError(w, err)
+	}
+	return writer.n + n, err
 }
 
 // Flush flushes the ResponseWriter if it has a Flush() method.
@@ -124,19 +129,25 @@ type jsonFormatter struct {
 
 func (f *jsonFormatter) WriteResponse(w io.Writer, resp Response) (err error) {
 	var b []byte
+
 	if f.Pretty {
 		b, err = json.MarshalIndent(resp, "", "    ")
 	} else {
 		b, err = json.Marshal(resp)
 	}
 
 	if err != nil {
-		_, err = io.WriteString(w, err.Error())
-	} else {
-		_, err = w.Write(b)
+		err = unnestError(err)
+	} else if _, err = w.Write(b); err == nil {
+		_, err = w.Write([]byte("\n"))
 	}
+	return
+}
 
-	w.Write([]byte("\n"))
+func unnestError(err error) error {
+	for errNested := err; errNested != nil; errNested = errors.Unwrap(err) {
+		err = errNested
+	}
 	return err
 }