make net_input_bytes_curr_cmd more readable (#1756)

The metric `net_input_bytes_curr_cmd` is now computed by aggregating its components separately.

Signed-off-by: zhaozhao.zz <[email protected]>

Author: soloestoy

src/networking.c

@@ -2855,30 +2855,30 @@ void processMultibulkBuffer(client *c) {
          *
          * Calculation: For multi bulk buffer, we accumulate four factors, namely;
          *
-         * 1) multibulklen_slen + 1
+         * 1) multibulklen_slen + 3
          *    Cumulative string length (and not the value of) of multibulklen,
-         *    including +1 from RESP first byte.
-         * 2) bulklen_slen + c->argc
+         *    including the first "*" byte and last "\r\n" 2 bytes from RESP.
+         * 2) bulklen_slen + 3
          *    Cumulative string length (and not the value of) of bulklen,
-         *    including +1 from RESP first byte per argument count.
+         *    including +3 from RESP first "$" byte and last "\r\n" 2 bytes per argument count.
          * 3) c->argv_len_sum
          *    Cumulative string length of all argument vectors.
-         * 4) c->argc * 4 + 2
-         *    Cumulative string length of all white-spaces, for which there exists a total of
-         *    4 bytes per argument, plus 2 bytes from the leading '\r\n' from multibulklen.
+         * 4) c->argc * 2
+         *    Cumulative string length of the arguments' white-spaces, for which there exists a total of
+         *    "\r\n" 2 bytes per argument.
          *
          * For example;
          * Command) SET key value
          * RESP) *3\r\n$3\r\nSET\r\n$3\r\nkey\r\n$5\r\nvalue\r\n
          *
-         * 1) String length of "*3" is 2, obtained from (multibulklen_slen + 1).
-         * 2) String length of "$3" "$3" "$5" is 6, obtained from (bulklen_slen + c->argc).
+         * 1) String length of "*3\r\n" is 4, obtained from (multibulklen_slen + 3).
+         * 2) String length of "$3\r\n" "$3\r\n" "$5\r\n" is 12, obtained from (bulklen_slen + 3).
          * 3) String length of "SET" "key" "value" is 11, obtained from (c->argv_len_sum).
-         * 4) String length of all white-spaces "\r\n" is 14, obtained from (c->argc * 4 + 2).
+         * 4) String length of the 3 arguments' white-spaces "\r\n" is 6, obtained from (c->argc * 2).
          *
          * The 1st component is calculated within the below line.
          * */
-        c->net_input_bytes_curr_cmd += (multibulklen_slen + 1);
+        c->net_input_bytes_curr_cmd += (multibulklen_slen + 3);
     }
 
     serverAssertWithInfo(c, NULL, c->multibulklen > 0);
@@ -2943,9 +2943,8 @@ void processMultibulkBuffer(client *c) {
                 }
             }
             c->bulklen = ll;
-            /* Per-slot network bytes-in calculation, 2nd component.
-             * c->argc portion is deferred, as it may not have been fully populated at this point. */
-            c->net_input_bytes_curr_cmd += bulklen_slen;
+            /* Per-slot network bytes-in calculation, 2nd component. */
+            c->net_input_bytes_curr_cmd += (bulklen_slen + 3);
         }
 
         /* Read bulk argument */
@@ -2983,9 +2982,8 @@ void processMultibulkBuffer(client *c) {
 
     /* We're done when c->multibulk == 0 */
     if (c->multibulklen == 0) {
-        /* Per-slot network bytes-in calculation, 3rd and 4th components.
-         * Here, the deferred c->argc from 2nd component is added, resulting in c->argc * 5 instead of * 4. */
-        c->net_input_bytes_curr_cmd += (c->argv_len_sum + (c->argc * 5 + 2));
+        /* Per-slot network bytes-in calculation, 3rd and 4th components. */
+        c->net_input_bytes_curr_cmd += (c->argv_len_sum + (c->argc * 2));
         c->read_flags |= READ_FLAGS_PARSING_COMPLETED;
     }
 }