Refactor pool_process_query().

- Fix hangup when received Flush(H) message.
  See following for more details:
  Subject: [Pgpool-general] Issue with pgpool-II-3.0.3-beta1 prepared
           statements execution
  Date: Tue, 22 Feb 2011 13:55:25 +0300

- Fix possible hangup that happen for the receiving timing of
  ReadyForQuery(Z) message.
  How to reproduce:
  frontend -> pgpool-II -> pgpool-II -> backend
  Both pgpool-II are in connection pooling mode.

diff --git a/pool_process_query.c b/pool_process_query.c
index 538d853c9a8ccac26044edd046e98333e19eb632..3729038b56b8615c24c701b8877ed6fcb637af0e 100644 (file)
--- a/pool_process_query.c
+++ b/pool_process_query.c
@@ -86,7 +86,6 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
                                                           POOL_CONNECTION_POOL *backend,
                                                           int reset_request)
 {
-       char kind;      /* packet kind (backend) */
        short num_fields = 0;   /* the number of fields in a row (V2 protocol) */
        fd_set  readmask;
        fd_set  writemask;
@@ -110,8 +109,6 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
 
        for (;;)
        {
-               kind = 0;
-
                /* Are we requested to send reset queries? */
                if (state == 0 && reset_request)
                {
@@ -172,8 +169,8 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
                }
 
                /*
-                * if all backends do not have any pending data in the
-                * receiving data cache, then issue select(2) to wait for new
+                * if a frontend and all backends do not have any pending data in
+                * the receiving data cache, then issue select(2) to wait for new
                 * data arrival
                 */
                if (is_cache_empty(frontend, backend) && !pool_is_query_in_progress())
@@ -196,10 +193,7 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
 
                        num_fds = 0;
 
-                       /*
-                        * Do not read a message from frontend while backends process a query.
-                        */
-                       if (!reset_request && !pool_is_query_in_progress())
+                       if (!reset_request)
                        {
                                FD_SET(frontend->fd, &readmask);
                                FD_SET(frontend->fd, &exceptmask);
@@ -263,7 +257,8 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
 
                                        if (idle_count > pool_config->client_idle_limit)
                                        {
-                                               pool_log("pool_process_query: child connection forced to terminate due to client_idle_limit(%d) reached", pool_config->client_idle_limit);
+                                               pool_log("pool_process_query: child connection forced to terminate due to client_idle_limit(%d) reached",
+                                                                pool_config->client_idle_limit);
                                                pool_send_error_message(frontend, MAJOR(backend),
                                                                                                "57000", "connection terminated due to online recovery",
                                                                                                "","",  __FILE__, __LINE__);
@@ -276,7 +271,8 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
 
                                        if (idle_count_in_recovery > pool_config->client_idle_limit_in_recovery)
                                        {
-                                               pool_log("pool_process_query: child connection forced to terminate due to client_idle_limit_in_recovery(%d) reached", pool_config->client_idle_limit_in_recovery);
+                                               pool_log("pool_process_query: child connection forced to terminate due to client_idle_limit_in_recovery(%d) reached",
+                                                                pool_config->client_idle_limit_in_recovery);
                                                pool_send_error_message(frontend, MAJOR(backend),
                                                                                                "57000", "connection terminated due to online recovery",
                                                                                                "","",  __FILE__, __LINE__);
@@ -329,10 +325,6 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
                                                        sleep(5);
                                                        break;
                                                }
-                                               status = ProcessBackendResponse(frontend, backend, &state, &num_fields);
-                                               if (status != POOL_CONTINUE)
-                                                       return status;
-                                               break;
                                        }
                                }
                        }
@@ -340,7 +332,7 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
                        if (was_error)
                                continue;
 
-                       if (!reset_request && !pool_is_query_in_progress())
+                       if (!reset_request)
                        {
                                if (FD_ISSET(frontend->fd, &exceptmask))
                                        return POOL_END;
@@ -349,19 +341,16 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
                                        status = ProcessFrontendResponse(frontend, backend);
                                        if (status != POOL_CONTINUE)
                                                return status;
-
-#ifdef NOT_USED
-                                       continue;
-                               }
-                               if (kind == 0)
-                                       continue;
-#endif
                                }
                        }
 
                        if (FD_ISSET(MASTER(backend)->fd, &exceptmask))
-                       {
                                return POOL_ERROR;
+                       else if (FD_ISSET(MASTER(backend)->fd, &readmask))
+                       {
+                               status = ProcessBackendResponse(frontend, backend, &state, &num_fields);
+                               if (status != POOL_CONTINUE)
+                                       return status;
                        }
                }
                else
@@ -375,16 +364,20 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
                                {
                                        pool_log("pool_process_query: garbage data from frontend after receiving terminate message ignored");
                                        pool_discard_read_buffer(frontend);
-                                       continue;
                                }
+                               else
+                               {
+                                       status = ProcessFrontendResponse(frontend, backend);
+                                       if (status != POOL_CONTINUE)
+                                               return status;
+                               }
+                       }
 
-                               status = ProcessFrontendResponse(frontend, backend);
+                       if (!pool_read_buffer_is_empty(MASTER(backend)) || pool_is_query_in_progress())
+                       {
+                               status = ProcessBackendResponse(frontend, backend, &state, &num_fields);
                                if (status != POOL_CONTINUE)
                                        return status;
-
-#ifdef NOT_USED
-                               continue;
-#endif
                        }
                }
 
@@ -398,11 +391,6 @@ POOL_STATUS pool_process_query(POOL_CONNECTION *frontend,
                                pool_memset_system_db_info(system_db_info->info);
                        got_sighup = 0;
                }
-
-               status = ProcessBackendResponse(frontend, backend, &state, &num_fields);
-               if (status != POOL_CONTINUE)
-                       return status;
-
        }
        return POOL_CONTINUE;
 }