Fix race condition: instance map wasn't locked for the

duration of the whole 'flush instances'. As a consequence,
it was possible to query instance map, while it is in the
inconsistent state. The patch was reworked after review.


server-tools/instance-manager/guardian.cc:
  do not lock instance map in Guardian_thread::init()
server-tools/instance-manager/instance_map.cc:
  Eliminate race condition: lock instance map and guardian
  for the duration of the whole "FLUSH INSTANCES" execution.
server-tools/instance-manager/instance_map.h:
  add new method. cleanup interface. add comments.
server-tools/instance-manager/manager.cc:
  use instance_map.flush_instances instead of instance_map.load() and guardian_thread.init()

1 files changed, 7 insertions, 15 deletions

diff --git a/server-tools/instance-manager/manager.cc b/server-tools/instance-manager/manager.cc
index 3ecd5fbc0d0..95f9029f648 100644
--- a/server-tools/instance-manager/manager.cc
+++ b/server-tools/instance-manager/manager.cc
@@ -135,15 +135,6 @@ void manager(const Options &options)
   if (instance_map.init() || user_map.init())
     return;
 
-
-  if (instance_map.load())
-  {
-    log_error("Cannot init instances repository. This might be caused by "
-               "the wrong config file options. For instance, missing mysqld "
-               "binary. Aborting.");
-    return;
-  }
-
   if (user_map.load(options.password_file_name))
     return;
 
@@ -207,12 +198,13 @@ void manager(const Options &options)
 
   shutdown_complete= FALSE;
 
-  /* init list of guarded instances */
-  guardian_thread.lock();
-
-  guardian_thread.init();
-
-  guardian_thread.unlock();
+  if (instance_map.flush_instances())
+  {
+    log_error("Cannot init instances repository. This might be caused by "
+               "the wrong config file options. For instance, missing mysqld "
+               "binary. Aborting.");
+    return;
+  }
 
   /*
     After the list of guarded instances have been initialized,