Fixed a deadlock when the same thread tried to route a reply and a query at the same time.

server/modules/include/shardrouter.h

@@ -173,6 +173,7 @@ struct router_client_session {
         bool             rses_closed;    /*< true when closeSession is called      */
 	    DCB*			 rses_client_dcb;
             DCB* dummy_dcb; /* DCB used to send the client write messages from the router itself */
+            DCB* queue_dcb; /* DCB used to send queued queries to the router */
 	    MYSQL_session*   rses_mysql_session;
 	/** Properties listed by their type */
 	rses_property_t* rses_properties[RSES_PROP_TYPE_COUNT];

server/modules/routing/dbshard/shardrouter.c

@@ -480,6 +480,7 @@ filterReply(FILTER* instance, void *session, GWBUF *reply)
     sescmd_cursor_t* scur;
     GWBUF* tmp = NULL;
 
+    skygw_log_write_flush(LOGFILE_TRACE,"shardrouter: filterReply mapped: %s",rses->hash_init ? "true" : "false");
 
     if(!rses_begin_locked_router_action(rses))
     {
@@ -555,7 +556,8 @@ retblock:
     rses_end_locked_router_action(rses);
     if(tmp)
     {        
-        rv = routeQuery((ROUTER*) rses->router, rses, tmp);
+        poll_add_epollin_event_to_dcb(rses->queue_dcb,tmp);
+        //routeQuery((ROUTER*) rses->router, rses, tmp);
     }
     return rv;
 }
@@ -566,7 +568,7 @@ retblock:
  * @param dcb The dummy DCB
  * @return 1 on success, 0 on failure
  */
-int fakeRead(DCB* dcb)
+int fakeReply(DCB* dcb)
 {
     if(dcb->dcb_readqueue)
     {
@@ -578,6 +580,27 @@ int fakeRead(DCB* dcb)
 }
 
 
+
+/**
+ * This function reads the DCB's readqueue and sends it as a query directly to the router.
+ * The function is used to route queued queries to the subservices when replies are received.
+ * @param dcb The dummy DCB
+ * @return 1 on success, 0 on failure
+ */
+int fakeQuery(DCB* dcb)
+{
+    if(dcb->dcb_readqueue)
+    {
+        GWBUF* tmp = dcb->dcb_readqueue;
+        void* rinst = dcb->session->service->router_instance;
+        void *rses = dcb->session->router_session;
+        
+        dcb->dcb_readqueue = NULL;
+        return dcb->session->service->router->routeQuery(rinst,rses,tmp);
+    }
+    return 1;
+}
+
 /**
  * Implementation of the mandatory version entry point
  *
@@ -819,9 +842,15 @@ newSession(
     client_rses->rses_transaction_active = false;
     client_rses->session = session;
     client_rses->dummy_dcb = dcb_alloc(DCB_ROLE_REQUEST_HANDLER);
-    client_rses->dummy_dcb->func.read = fakeRead;
+    client_rses->dummy_dcb->func.read = fakeReply;
     client_rses->dummy_dcb->state = DCB_STATE_POLLING;
     client_rses->dummy_dcb->session = session;
+    
+    client_rses->queue_dcb = dcb_alloc(DCB_ROLE_REQUEST_HANDLER);
+    client_rses->queue_dcb->func.read = fakeQuery;
+    client_rses->queue_dcb->state = DCB_STATE_POLLING;
+    client_rses->queue_dcb->session = session;
+    
     spinlock_init(&client_rses->rses_lock);
 
     client_rses->subservice = calloc(router->n_services, sizeof(SUBSERVICE*));
@@ -1000,6 +1029,10 @@ closeSession(
             }
             router_cli_ses->subservice[i]->state = SUBSVC_CLOSED;
         }
+        router_cli_ses->dummy_dcb->session = NULL;
+        router_cli_ses->queue_dcb->session = NULL;
+        dcb_close(router_cli_ses->dummy_dcb);
+        dcb_close(router_cli_ses->queue_dcb);
         
         /** Unlock */
         rses_end_locked_router_action(router_cli_ses);
@@ -1289,7 +1322,7 @@ routeQuery(ROUTER* instance,
     route_target_t route_target = TARGET_UNDEFINED;
     bool succp = false;
     char* tname = NULL;
-
+    skygw_log_write_flush(LOGFILE_TRACE,"shardrouter: routeQuery");
     CHK_CLIENT_RSES(router_cli_ses);
 
     /** Dirty read for quick check if router is closed. */
@@ -1311,6 +1344,7 @@ routeQuery(ROUTER* instance,
     
     if(!router_cli_ses->hash_init)
     {
+        skygw_log_write(LOGFILE_TRACE,"shardrouter: got a query while mapping databases.");
         GWBUF* tmp = router_cli_ses->queue;
         
         while(tmp && tmp->next)
@@ -1421,31 +1455,6 @@ routeQuery(ROUTER* instance,
         }
     }
 
-
-    if(LOG_IS_ENABLED(LOGFILE_TRACE))
-    {
-        uint8_t* packet = GWBUF_DATA(querybuf);
-        unsigned char ptype = packet[4];
-        size_t len = MIN(GWBUF_LENGTH(querybuf),
-                         MYSQL_GET_PACKET_LEN((unsigned char *) querybuf->start) - 1);
-        char* data = (char*) &packet[5];
-        char* contentstr = strndup(data, len);
-        char* qtypestr = skygw_get_qtype_str(qtype);
-
-        skygw_log_write(LOGFILE_TRACE,
-                        "> Autocommit: %s, trx is %s, cmd: %s, type: %s, "
-                        "stmt: %s%s %s",
-                        (router_cli_ses->rses_autocommit_enabled ? "[enabled]" : "[disabled]"),
-                        (router_cli_ses->rses_transaction_active ? "[open]" : "[not open]"),
-                        STRPACKETTYPE(ptype),
-                        (qtypestr == NULL ? "N/A" : qtypestr),
-                        contentstr,
-                        (querybuf->hint == NULL ? "" : ", Hint:"),
-                        (querybuf->hint == NULL ? "" : STRHINTTYPE(querybuf->hint->type)));
-
-        free(contentstr);
-        free(qtypestr);
-    }
     /**
      * Find out whether the query should be routed to single server or to 
      * all of them.