Reserve new client error for connection throttling

Summary: We need a new error reserved for higher level connection throttling.  Add a new client error in MySQL to support this.

Reviewed By: abal147

Differential Revision: D39623157

Author: jkedgar

include/errmsg.h

@@ -262,7 +262,10 @@ extern const char *client_errors[]; /* Error messages */
 #define CR_NET_READ_INTERRUPTED 2200
 #define CR_NET_WRITE_INTERRUPTED 2201
 #define CR_TLS_SERVER_NOT_FOUND 2202
-#define CR_ERROR_LAST /*Copy last error nr:*/ 2202
+// CR_CONN_THROTTLED is not directly used in MySQL - reserved for FB usage at
+// a higher level
+#define CR_CONN_THROTTLED 2203
+#define CR_ERROR_LAST /*Copy last error nr:*/ 2203
 /* Add error numbers before CR_ERROR_LAST and change it accordingly. */
 
 #define CR_PLACEHOLDER_FIRST CR_PLACEHOLDER_2074

include/mysql.h.pp

@@ -418,7 +418,7 @@
          client_errno <= 2199;
 }
 static inline const char *ER_CLIENT(int client_errno) {
-  if (client_errno >= 2000 && client_errno <= 2202 &&
+  if (client_errno >= 2000 && client_errno <= 2203 &&
       !isPlaceHolder(client_errno)) {
     return client_errors[client_errno - 2000];
   }

libmysql/errmsg.cc

@@ -249,6 +249,7 @@ const char *client_errors[] = {
     "Write timeout is reached",
     "Server rejected the ssl handshake for specified sni servername, sslerror: "
     "%-.100s",
+    "Connection attempt throttled",
     ""};
 
 static const char *get_client_errmsg(int nr) {