MXS-1752: Remove EOF packet generation

The creation of the EOF packet is not needed as the last packet of a
result set is always guaranteed to be of the correct type. This also
allows non-resultsets to be correctly processed as the internal packet
number will be at 0 when the last result arrives.

Cleaned up some of the function names and changed the signatures to be
better suited for their use-cases.

Use angle bracket includes, combine some of the more unwieldly
conditionals into functions, added more comments.

server/modules/routing/cat/catsession.cc

@@ -10,11 +10,11 @@
  * of this software will be governed by version 2 or later of the General
  * Public License.
  */
-
 #include "cat.hh"
 #include "catsession.hh"
-#include "maxscale/protocol/mysql.h"
-#include "maxscale/modutil.h"
+
+#include <maxscale/protocol/mysql.h>
+#include <maxscale/modutil.h>
 
 using namespace maxscale;
 
@@ -22,7 +22,9 @@ CatSession::CatSession(MXS_SESSION* session, Cat* router, SRWBackendList& backen
     RouterSession(session),
     m_session(session),
     m_backends(backends),
-    m_completed(0)
+    m_completed(0),
+    m_packet_num(0),
+    m_query(NULL)
 {
 }
 
@@ -34,13 +36,15 @@ void CatSession::close()
 {
 }
 
-void CatSession::skip_unused()
+bool CatSession::next_backend()
 {
     // Skip unused backends
     while (m_current != m_backends.end() && !(*m_current)->in_use())
     {
         m_current++;
     }
+
+    return m_current != m_backends.end();
 }
 
 int32_t CatSession::routeQuery(GWBUF* pPacket)
@@ -52,10 +56,7 @@ int32_t CatSession::routeQuery(GWBUF* pPacket)
     m_query = pPacket;
     m_current = m_backends.begin();
 
-    // If the first backend is not in use, find one that is
-    skip_unused();
-
-    if (m_current != m_backends.end())
+    if (next_backend())
     {
         // We have a backend, write the query only to this one. It will be
         // propagated onwards in clientReply.
@@ -71,39 +72,23 @@ void CatSession::clientReply(GWBUF* pPacket, DCB* pDcb)
     auto backend = *m_current;
     ss_dassert(backend->dcb() == pDcb);
     bool send = false;
-    bool propagate = true;
-
-    if (m_completed == 0 && backend->get_reply_state() == REPLY_STATE_START &&
-        !mxs_mysql_is_result_set(pPacket))
-    {
-        propagate = false;
-    }
 
     if (backend->reply_is_complete(pPacket))
     {
         backend->ack_write();
         m_completed++;
         m_current++;
-        skip_unused();
 
-        if (m_current == m_backends.end())
+        if (!next_backend())
         {
-            uint8_t eof_packet[] = {0x5, 0x0, 0x0, 0x0, 0xfe, 0x0, 0x0, 0x2, 0x0};
-            gwbuf_free(pPacket);
-            pPacket = gwbuf_alloc_and_load(sizeof(eof_packet), eof_packet);
             send = true;
             gwbuf_free(m_query);
             m_query = NULL;
         }
-        else if (propagate)
-        {
-            (*m_current)->write(gwbuf_clone(m_query));
-        }
         else
         {
-            send = true;
-            gwbuf_free(m_query);
-            m_query = NULL;
+            (*m_current)->write(gwbuf_clone(m_query));
+            (*m_current)->set_reply_state(REPLY_STATE_START);
         }
     }
 
@@ -119,6 +104,7 @@ void CatSession::clientReply(GWBUF* pPacket, DCB* pDcb)
 
     if (send)
     {
+        // Increment the packet sequence number and send it to the client
         GWBUF_DATA(pPacket)[3] = m_packet_num++;
         MXS_SESSION_ROUTE_REPLY(pDcb->session, pPacket);
     }
@@ -130,5 +116,10 @@ void CatSession::clientReply(GWBUF* pPacket, DCB* pDcb)
 
 void CatSession::handleError(GWBUF* pMessage, DCB* pProblem, mxs_error_action_t action, bool* pSuccess)
 {
+    /**
+     * The simples thing to do here is to close the connection. Anything else
+     * would still require extra processing on the client side and reconnecting
+     * will cause things to fix themselves.
+     */
     *pSuccess = false;
 }

server/modules/routing/cat/catsession.hh

@@ -77,6 +77,10 @@ private:
     mxs::SRWBackendList::iterator m_current;
     GWBUF*                        m_query;
 
-    // Skip over unused backend servers
-    void skip_unused();
-};
+    /**
+     * Iterate to next backend
+     *
+     * @return True if m_current points to a valid backend that is in use
+     */
+    bool next_backend();
+};