Bug#11762667: MYSQLBINLOG IGNORES ERRORS WHILE WRITING OUTPUT

Problem: mysqlbinlog exits without any error code in case of
file write error. It is because of the fact that the calls
to Log_event::print() method does not return a value and the
thus any error were being ignored.

Resolution: We resolve this problem by checking for the 
IO_CACHE::error == -1 after every call to Log_event:: print()
and terminating the further execution.

client/mysqlbinlog.cc:
  - handled error conditions during event->print() calls
  - added check for error in end_io_cache()
mysys/my_write.c:
  Added debug code to simulate file write error.
  error returned will be ENOSPC=> error no space on the disk
sql/log_event.cc:
  Added debug code to simulate file write error, by reducing the size of io cache.

client/mysqlbinlog.cc

@@ -690,6 +690,7 @@ Exit_status process_event(PRINT_EVENT_INFO *print_event_info, Log_event *ev,
   DBUG_ENTER("process_event");
   print_event_info->short_form= short_form;
   Exit_status retval= OK_CONTINUE;
+  IO_CACHE *const head= &print_event_info->head_cache;
 
   /*
     Format events are not concerned by --offset and such, we always need to
@@ -753,6 +754,8 @@ Exit_status process_event(PRINT_EVENT_INFO *print_event_info, Log_event *ev,
       }
       else
         ev->print(result_file, print_event_info);
+      if (head->error == -1)
+        goto err;
       break;
 
     case CREATE_FILE_EVENT:
@@ -804,6 +807,8 @@ Exit_status process_event(PRINT_EVENT_INFO *print_event_info, Log_event *ev,
         output of Append_block_log_event::print is only a comment.
       */
       ev->print(result_file, print_event_info);
+      if (head->error == -1)
+        goto err;
       if ((retval= load_processor.process((Append_block_log_event*) ev)) !=
           OK_CONTINUE)
         goto end;
@@ -812,6 +817,8 @@ Exit_status process_event(PRINT_EVENT_INFO *print_event_info, Log_event *ev,
     case EXEC_LOAD_EVENT:
     {
       ev->print(result_file, print_event_info);
+      if (head->error == -1)
+        goto err;
       Execute_load_log_event *exv= (Execute_load_log_event*)ev;
       Create_file_log_event *ce= load_processor.grab_event(exv->file_id);
       /*
@@ -841,6 +848,8 @@ Exit_status process_event(PRINT_EVENT_INFO *print_event_info, Log_event *ev,
       print_event_info->common_header_len=
         glob_description_event->common_header_len;
       ev->print(result_file, print_event_info);
+      if (head->error == -1)
+        goto err;
       if (!remote_opt)
         ev->free_temp_buf(); // free memory allocated in dump_local_log_entries
       else
@@ -864,6 +873,8 @@ Exit_status process_event(PRINT_EVENT_INFO *print_event_info, Log_event *ev,
       break;
     case BEGIN_LOAD_QUERY_EVENT:
       ev->print(result_file, print_event_info);
+      if (head->error == -1)
+        goto err;
       if ((retval= load_processor.process((Begin_load_query_log_event*) ev)) !=
           OK_CONTINUE)
         goto end;
@@ -974,6 +985,8 @@ Exit_status process_event(PRINT_EVENT_INFO *print_event_info, Log_event *ev,
     }
     default:
       ev->print(result_file, print_event_info);
+      if (head->error == -1)
+        goto err;
     }
   }
 
@@ -2012,7 +2025,13 @@ err:
 end:
   if (fd >= 0)
     my_close(fd, MYF(MY_WME));
-  end_io_cache(file);
+  /*
+    Since the end_io_cache() writes to the
+    file errors may happen.
+   */
+  if (end_io_cache(file))
+    retval= ERROR_STOP;
+
   return retval;
 }
 

mysys/my_write.c

@@ -38,7 +38,17 @@ size_t my_write(int Filedes, const uchar *Buffer, size_t Count, myf MyFlags)
   
   for (;;)
   {
-    if ((writenbytes= write(Filedes, Buffer, Count)) == Count)
+    writenbytes= write(Filedes, Buffer, Count);
+    /**
+       To simulate the write error set the errno = error code
+       and the number pf written bytes to -1.
+     */
+    DBUG_EXECUTE_IF ("simulate_file_write_error",
+                     {
+                       errno= ENOSPC;
+                       writenbytes= (size_t) -1;
+                     });
+    if (writenbytes == Count)
       break;
     if (writenbytes != (size_t) -1)
     {						/* Safeguard */

sql/log_event.cc

@@ -3090,6 +3090,12 @@ void Query_log_event::print(FILE* file, PRINT_EVENT_INFO* print_event_info)
 {
   Write_on_release_cache cache(&print_event_info->head_cache, file);
 
+  /**
+    reduce the size of io cache so that the write function is called
+    for every call to my_b_write().
+   */
+  DBUG_EXECUTE_IF ("simulate_file_write_error",
+                   {(&cache)->write_pos= (&cache)->write_end- 500;});
   print_query_header(&cache, print_event_info);
   my_b_write(&cache, (uchar*) query, q_len);
   my_b_printf(&cache, "\n%s\n", print_event_info->delimiter);