fix: avoid useless io in large-payload queries (#500)

* fix: avoid useless io in large-payload queries

* fix: only limit request body size

* fix: body is not exclusive to the POST method

* docs: update the description of retry_number

config/README.md

@@ -347,6 +347,9 @@ kill_query_user: <kill_query_user_config> | optional
 heartbeat: <heartbeat_config> | optional
 
 # RetryNumber - user configuration for query retry when one host cannot respond.
+# By default there are no query retries.
+# Note: Retrying may impact performance if there are many large-payload requests (such as inserts),
+# because it requires copying the request body for reuse.
 retry_number: 0
 
 ```
@@ -381,11 +384,11 @@ max_execution_time: <duration> | optional | default = 120s
 # By default there are no per-minute limits
 requests_per_minute: <int> | optional | default = 0
 
-# The burst of request packet size token bucket for user
+# The burst of request packet body size token bucket for user
 # By default there are no request packet size limits
 request_packet_size_tokens_burst: <byte_size> | optional | default = 0
 
-# The request packet size tokens produced rate per second for user
+# The request packet body size tokens produced rate per second for user
 # By default there are no request packet size limits
 request_packet_size_tokens_rate: <byte_size> | optional | default = 0
 

proxy.go

@@ -205,21 +205,22 @@ func executeWithRetry(
 	startTime := time.Now()
 	var since float64
 
+	var body []byte
+	var err error
 	// Use readAndRestoreRequestBody to read the entire request body into a byte slice,
 	// and to restore req.Body so that it can be reused later in the code.
-	body, err := readAndRestoreRequestBody(req)
-	if err != nil {
-		since := time.Since(startTime).Seconds()
-		return since, err
+	if maxRetry > 0 {
+		body, err = readAndRestoreRequestBody(req)
+		if err != nil {
+			since := time.Since(startTime).Seconds()
+			return since, err
+		}
 	}
 
 	numRetry := 0
 	for {
 		rp(rw, req)
 
-		// Restore req.Body after it's consumed by 'rp' for potential reuse.
-		req.Body = io.NopCloser(bytes.NewBuffer(body))
-
 		err := ctx.Err()
 		if err != nil {
 			since = time.Since(startTime).Seconds()
@@ -269,6 +270,8 @@ func executeWithRetry(
 			since = time.Since(startTime).Seconds()
 			break
 		}
+		// Restore req.Body after it's consumed by 'rp' for potential reuse.
+		req.Body = io.NopCloser(bytes.NewBuffer(body))
 		numRetry++
 	}
 	return since, nil
@@ -915,11 +918,5 @@ func (rp *reverseProxy) getScope(req *http.Request) (*scope, int, error) {
 	}
 
 	s := newScope(req, u, c, cu, sessionId, sessionTimeout)
-
-	q, err := getFullQuery(req)
-	if err != nil {
-		return nil, http.StatusBadRequest, fmt.Errorf("%s: cannot read query: %w", s, err)
-	}
-	s.requestPacketSize = len(q)
 	return s, 0, nil
 }

scope.go

@@ -86,6 +86,8 @@ func newScope(req *http.Request, u *user, c *cluster, cu *clusterUser, sessionId
 			"replica":      h.ReplicaName(),
 			"cluster_node": h.Host(),
 		},
+
+		requestPacketSize: max(0, int(req.ContentLength)),
 	}
 	return s
 }