Only store established connections in the pool

If a connection has not been fully established (i.e. authentication has
been completed) then it should not be considered as a connection pool
candidate.

include/maxscale/protocol.h

@@ -43,7 +43,10 @@ struct session;
  *      close           MaxScale close entry point for the socket
  *      listen          Create a listener for the protocol
  *      auth            Authentication entry point
- *  session         Session handling entry point
+ *      session         Session handling entry point
+ *      auth_default    Default authenticator name
+ *      connlimit       Maximum connection limit
+ *      established     Whether connection is fully established
  * @endverbatim
  *
  * This forms the "module object" for protocol modules within the gateway.
@@ -62,9 +65,10 @@ typedef struct mxs_protocol
     int32_t (*close)(struct dcb *);
     int32_t (*listen)(struct dcb *, char *);
     int32_t (*auth)(struct dcb *, struct server *, struct session *, GWBUF *);
-    int32_t (*session)(struct dcb *, void *);
+    int32_t (*session)(struct dcb *, void *); // TODO: remove this, not used
     char   *(*auth_default)();
     int32_t (*connlimit)(struct dcb *, int limit);
+    bool    (*established)(struct dcb *);
 } MXS_PROTOCOL;
 
 /**

server/core/dcb.c

@@ -1658,6 +1658,7 @@ static bool
 dcb_maybe_add_persistent(DCB *dcb)
 {
     if (dcb->user != NULL
+        && (dcb->func.established == NULL || dcb->func.established(dcb))
         && strlen(dcb->user)
         && dcb->server
         && dcb->server->persistpoolmax

server/modules/protocol/CDC/cdc.c

@@ -85,7 +85,9 @@ MXS_MODULE* MXS_CREATE_MODULE()
         cdc_listen, /* Create a listener             */
         NULL, /* Authentication                */
         NULL, /* Session                       */
-        cdc_default_auth /* default authentication */
+        cdc_default_auth, /* default authentication */
+        NULL,
+        NULL,
     };
 
     static MXS_MODULE info =

server/modules/protocol/HTTPD/httpd.c

@@ -81,7 +81,8 @@ MXS_MODULE* MXS_CREATE_MODULE()
         NULL,               /**< Authentication                */
         NULL,               /**< Session                       */
         httpd_default_auth, /**< Default authenticator         */
-        NULL                /**< Connection limit reached      */
+        NULL,               /**< Connection limit reached      */
+        NULL
     };
 
     static MXS_MODULE info =

server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c

@@ -77,6 +77,7 @@ static int gw_send_change_user_to_backend(char          *dbname,
                                           char          *user,
                                           uint8_t       *passwd,
                                           MySQLProtocol *conn);
+static bool gw_connection_established(DCB* dcb);
 
 /*
  * The module entry point routine. It is this routine that
@@ -102,7 +103,8 @@ MXS_MODULE* MXS_CREATE_MODULE()
         gw_change_user,             /* Authentication                */
         NULL,                       /* Session                       */
         gw_backend_default_auth,    /* Default authenticator         */
-        NULL                        /* Connection limit reached      */
+        NULL,                       /* Connection limit reached      */
+        gw_connection_established
     };
 
     static MXS_MODULE info =
@@ -883,7 +885,8 @@ static int gw_MySQLWrite_backend(DCB *dcb, GWBUF *queue)
 
     CHK_DCB(dcb);
 
-    if (dcb->was_persistent && dcb->state == DCB_STATE_POLLING)
+    if (dcb->was_persistent && dcb->state == DCB_STATE_POLLING &&
+        backend_protocol->protocol_auth_state == MXS_AUTH_STATE_COMPLETE)
     {
         ss_dassert(dcb->persistentstart == 0);
         /**
@@ -1949,3 +1952,9 @@ gw_send_change_user_to_backend(char          *dbname,
     }
     return rc;
 }
+
+static bool gw_connection_established(DCB* dcb)
+{
+    MySQLProtocol *proto = (MySQLProtocol*)dcb->protocol;
+    return proto->protocol_auth_state == MXS_AUTH_STATE_COMPLETE;
+}

server/modules/protocol/MySQL/MySQLClient/mysql_client.c

@@ -115,7 +115,8 @@ MXS_MODULE* MXS_CREATE_MODULE()
         NULL,                                   /* Authentication                */
         NULL,                                   /* Session                       */
         gw_default_auth,                        /* Default authenticator         */
-        gw_connection_limit                     /* Send error connection limit   */
+        gw_connection_limit,                    /* Send error connection limit   */
+        NULL
     };
 
     static MXS_MODULE info =

server/modules/protocol/maxscaled/maxscaled.c

@@ -185,7 +185,8 @@ MXS_MODULE* MXS_CREATE_MODULE()
         NULL,                           /**< Authentication                */
         NULL,                           /**< Session                       */
         mxsd_default_auth,              /**< Default authenticator         */
-        NULL                            /**< Connection limit reached      */
+        NULL,                           /**< Connection limit reached      */
+        NULL
     };
 
     static MXS_MODULE info =

server/modules/protocol/telnetd/telnetd.c

@@ -102,7 +102,8 @@ MXS_MODULE* MXS_CREATE_MODULE()
         NULL,                           /**< Authentication                */
         NULL,                           /**< Session                       */
         telnetd_default_auth,           /**< Default authenticator         */
-        NULL                            /**< Connection limit reached      */
+        NULL,                           /**< Connection limit reached      */
+        NULL
     };
 
     static MXS_MODULE info =