fix(http): keep the http response body open until the result has been read

This modifies the `MultiResultDecoder` interface to accept an
`io.ReadCloser` so the `ResultIterator` can close the `io.Reader`
instead of doing it through a defer call. It then makes it so the
`Cancel()` method will close the reader or the reader will be
automatically closed when `More()` returns false.

http/query_service.go

@@ -156,7 +156,6 @@ func (s *QueryService) Query(ctx context.Context, orgID platform.ID, query *ifql
 	if err != nil {
 		return nil, err
 	}
-	defer resp.Body.Close()
 	return s.processResponse(resp)
 }
 
@@ -182,7 +181,6 @@ func (s *QueryService) QueryWithCompile(ctx context.Context, orgID platform.ID,
 	if err != nil {
 		return nil, err
 	}
-	defer resp.Body.Close()
 	return s.processResponse(resp)
 }
 

query/csv/result.go

@@ -75,7 +75,7 @@ func (d *ResultDecoder) Decode(r io.Reader) (query.Result, error) {
 // Results are delimited by an empty line.
 type MultiResultDecoder struct {
 	c ResultDecoderConfig
-	r io.Reader
+	r io.ReadCloser
 }
 
 // NewMultiResultDecoder creates a new MultiResultDecoder.
@@ -88,7 +88,7 @@ func NewMultiResultDecoder(c ResultDecoderConfig) *MultiResultDecoder {
 	}
 }
 
-func (d *MultiResultDecoder) Decode(r io.Reader) (query.ResultIterator, error) {
+func (d *MultiResultDecoder) Decode(r io.ReadCloser) (query.ResultIterator, error) {
 	return &resultIterator{
 		c: d.c,
 		r: r,
@@ -98,9 +98,11 @@ func (d *MultiResultDecoder) Decode(r io.Reader) (query.ResultIterator, error) {
 // resultIterator iterates through the results encoded in r.
 type resultIterator struct {
 	c    ResultDecoderConfig
-	r    io.Reader
+	r    io.ReadCloser
 	next *resultDecoder
 	err  error
+
+	canceled bool
 }
 
 func (r *resultIterator) More() bool {
@@ -110,8 +112,13 @@ func (r *resultIterator) More() bool {
 			extraMeta = r.next.extraMeta
 		}
 		r.next, r.err = newResultDecoder(r.r, r.c, extraMeta)
-		return r.err == nil
+		if r.err == nil {
+			return true
+		}
 	}
+
+	// Release the resources for this query.
+	r.Cancel()
 	return false
 }
 
@@ -120,6 +127,14 @@ func (r *resultIterator) Next() query.Result {
 }
 
 func (r *resultIterator) Cancel() {
+	if r.canceled {
+		return
+	}
+
+	if err := r.r.Close(); err != nil && r.err == nil {
+		r.err = err
+	}
+	r.canceled = true
 }
 
 func (r *resultIterator) Err() error {

query/csv/result_test.go

@@ -506,7 +506,7 @@ func TestResultDecoder(t *testing.T) {
 
 func TestResultEncoder(t *testing.T) {
 	testCases := []TestCase{
-	// Add tests cases specific to encoding here
+		// Add tests cases specific to encoding here
 	}
 	testCases = append(testCases, symetricalTestCases...)
 	for _, tc := range testCases {

query/influxql/result.go

@@ -139,7 +139,7 @@ func (e *MultiResultEncoder) Encode(w io.Writer, results query.ResultIterator) e
 		resp.Results = append(resp.Results, result)
 	}
 
-	if err := results.Err(); err != nil {
+	if err := results.Err(); err != nil && resp.Err == "" {
 		resp.error(err)
 	}
 

query/query.go

@@ -198,6 +198,7 @@ func (r *SliceResultIterator) Next() Result {
 }
 
 func (r *SliceResultIterator) Cancel() {
+	r.results = nil
 }
 
 func (r *SliceResultIterator) Err() error {

query/result.go

@@ -124,7 +124,7 @@ type ResultEncoder interface {
 // MultiResultDecoder can decode multiple results from a reader.
 type MultiResultDecoder interface {
 	// Decode decodes multiple results from r.
-	Decode(r io.Reader) (ResultIterator, error)
+	Decode(r io.ReadCloser) (ResultIterator, error)
 }
 
 // MultiResultEncoder can encode multiple results into a writer.