Refactor auxiliary routing functions

Refactored some of the functions used to calculate servers. Removed
redundant checks and moved the ack_write() call to the right place.

server/modules/routing/readwritesplit/readwritesplit.cc

@@ -102,11 +102,10 @@ static const MXS_ENUM_VALUE master_failure_mode_values[] =
  * @param   rses Router client session
  * @param   router_nservers The number of backend servers in total
  */
-int rses_get_max_slavecount(ROUTER_CLIENT_SES *rses,
+int rses_get_max_slavecount(ROUTER_CLIENT_SES *rses)
-                            int router_nservers)
 {
     int conf_max_nslaves;
-    int max_nslaves;
+    int router_nservers = rses->rses_nbackends;
 
     CHK_CLIENT_RSES(rses);
 
@@ -118,9 +117,8 @@ int rses_get_max_slavecount(ROUTER_CLIENT_SES *rses,
     {
         conf_max_nslaves = (router_nservers * rses->rses_config.rw_max_slave_conn_percent) / 100;
     }
-    max_nslaves = MXS_MIN(router_nservers - 1, MXS_MAX(1, conf_max_nslaves));
 
-    return max_nslaves;
+    return MXS_MIN(router_nservers - 1, MXS_MAX(1, conf_max_nslaves));
 }
 
 /*
@@ -474,7 +472,7 @@ static bool handle_error_new_connection(ROUTER_INSTANCE *inst,
     /** Close the current connection */
     bref->close();
 
-    int max_nslaves = rses_get_max_slavecount(myrses, myrses->rses_nbackends);
+    int max_nslaves = rses_get_max_slavecount(myrses);
     bool succp;
     /**
      * Try to get replacement slave or at least the minimum
@@ -796,10 +794,11 @@ static MXS_ROUTER_SESSION *newSession(MXS_ROUTER *router_inst, MXS_SESSION *sess
         }
     }
 
-    int max_nslaves = rses_get_max_slavecount(client_rses, router_nservers);
-
     client_rses->rses_nbackends = router_nservers; /*< # of backend servers */
 
+    int max_nslaves = rses_get_max_slavecount(client_rses);
+
+
     if (!select_connect_backend_servers(router_nservers, max_nslaves,
                                         client_rses->rses_config.slave_selection_criteria,
                                         session, router, client_rses, false))
@@ -1122,7 +1121,8 @@ static void clientReply(MXS_ROUTER *instance,
 
     if (reply_is_complete(bref, writebuf))
     {
-        /** Got a complete reply, decrement expected response count */
+        /** Got a complete reply, acknowledge the write decrement expected response count */
+        bref->ack_write();
         router_cli_ses->expected_responses--;
         ss_dassert(router_cli_ses->expected_responses >= 0);
         ss_dassert(bref->get_reply_state() == REPLY_STATE_DONE);
@@ -1140,13 +1140,7 @@ static void clientReply(MXS_ROUTER *instance,
     {
         check_session_command_reply(writebuf, bref);
 
-        if (GWBUF_IS_TYPE_SESCMD_RESPONSE(writebuf))
+        /** This discards all responses that have already been sent to the client */
-        {
-            /**
-             * Discard all those responses that have already been sent to
-             * the client. Return with buffer including response that
-             * needs to be sent to client or NULL.
-             */
         bool rconn = false;
         process_sescmd_response(router_cli_ses, bref, &writebuf, &rconn);
 
@@ -1162,10 +1156,6 @@ static void clientReply(MXS_ROUTER *instance,
                 true);
         }
     }
-    }
-
-    /** Complete the write */
-    bref->ack_write();
 
     bool queue_routed = false;
 

server/modules/routing/readwritesplit/rwsplit_internal.hh

@@ -52,7 +52,7 @@ bool send_readonly_error(DCB *dcb);
  */
 int router_handle_state_switch(DCB *dcb, DCB_REASON reason, void *data);
 SRWBackend& get_bref_from_dcb(ROUTER_CLIENT_SES *rses, DCB *dcb);
-int rses_get_max_slavecount(ROUTER_CLIENT_SES *rses, int router_nservers);
+int rses_get_max_slavecount(ROUTER_CLIENT_SES *rses);
 int rses_get_max_replication_lag(ROUTER_CLIENT_SES *rses);
 
 /*

server/modules/routing/readwritesplit/rwsplit_select_backends.cc

@@ -79,7 +79,7 @@ static bool valid_for_slave(const SERVER *server, const SERVER *master_host)
  * @param cmpfun qsort() compatible comparison function
  * @return The best slave backend reference or NULL if no candidates could be found
  */
-SRWBackend* get_slave_candidate(ROUTER_CLIENT_SES* rses, const SERVER *master,
+SRWBackend get_slave_candidate(ROUTER_CLIENT_SES* rses, const SERVER *master,
                                int (*cmpfun)(const void *, const void *))
 {
     SRWBackend candidate;
@@ -210,7 +210,7 @@ bool select_connect_backend_servers(int router_nservers,
     ss_dassert(slaves_connected < max_nslaves || max_nslaves == 0);
 
     /** Connect to all possible slaves */
-    for (SRWBackend bref(get_slave_candidate(rses, router_nservers, master_host, cmpfun));
+    for (SRWBackend bref(get_slave_candidate(rses, master_host, cmpfun));
          bref && slaves_connected < max_nslaves;
          bref = get_slave_candidate(rses, master_host, cmpfun))
     {