tier/ctr: Solving DB Lock issue due to write contention from db connections

Problem: The DB on the brick is been accessed by CTR, for write and
tier migrator, for read and write. The write from tier migrator is reseting
the heat counters after a cycle. Since we are using sqlite, two connections
trying to write would cause a db lock contention. As a result CTR used to fail
to update the db.

Solution: Using the same db connection of CTR for reseting the heat counters.
1) Introducted a new IPC FOP for CTR
2) After the query do a ipc syncop to the underlying client xlator associated
   to the brick.
3) CTR in brick will catch the IPC FOP and cleat the heat counters.

Change-Id: I53306bfc08dcdba479deb4ccc154896521336150
BUG: 1260730
Signed-off-by: Joseph Fernandes <josferna@redhat.com>
Reviewed-on: http://review.gluster.org/12031
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Dan Lambright <dlambrig@redhat.com>
Tested-by: Dan Lambright <dlambrig@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/libglusterfs/src/gfdb/gfdb_sqlite3.h b/libglusterfs/src/gfdb/gfdb_sqlite3.h
index 213693136fe..7bcba5a54bd 100644
--- a/libglusterfs/src/gfdb/gfdb_sqlite3.h
+++ b/libglusterfs/src/gfdb/gfdb_sqlite3.h
@@ -279,6 +279,8 @@ int gf_sqlite3_find_recently_changed_files_freq (void *db_conn,
                                         int read_freq_cnt,
                                         gf_boolean_t clear_counters);
 
+int gf_sqlite3_clear_files_heat (void *db_conn);
+
 void gf_sqlite3_fill_db_operations (gfdb_db_operations_t  *gfdb_db_ops);
 
 #endif