glusterd: Start rebalance only where required

Gluster was starting rebalance processes on peers where it wasn't
required in two cases.
- For a normal rebalance command on a volume, rebalance processes were
  started on all peers instead of just the peers which contain bricks of
  the volume
- For rebalance process being restarted by a volume sync, caused by a
  new peer being probed or a peer restarting, rebalance processes were
  started on all peers, for both a normal rebalance and for remove-brick
  needing rebalance.

This patch adds a new check before starting rebalance process in the
above two cases.
- For rebalance process required by a rebalance command, each peer will
  check if it contains atleast one brick of the volume
- For rebalance process required by a remove-brick command, each peer
  will check if it contains atleast one of the bricks being removed

Change-Id: I512da16994f0d5482889c3a009c46dc20a8a15bb
BUG: 1031887
Signed-off-by: Kaushal M <kaushal@redhat.com>
Reviewed-on: http://review.gluster.org/6301
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-by: Anand Avati <avati@redhat.com>

3 files changed, 71 insertions, 1 deletions

diff --git a/xlators/mgmt/glusterd/src/glusterd-rebalance.c b/xlators/mgmt/glusterd/src/glusterd-rebalance.c
index 031de2c9b0e..214f40c668a 100644
--- a/xlators/mgmt/glusterd/src/glusterd-rebalance.c
+++ b/xlators/mgmt/glusterd/src/glusterd-rebalance.c
@@ -665,9 +665,11 @@ glusterd_op_rebalance (dict_t *dict, char **op_errstr, dict_t *rsp_dict)
                         uuid_parse (task_id_str, volinfo->rebal.rebalance_id) ;
                         volinfo->rebal.op = GD_OP_REBALANCE;
                 }
+                if (!gd_should_i_start_rebalance (volinfo))
+                        break;
                 ret = glusterd_handle_defrag_start (volinfo, msg, sizeof (msg),
                                                     cmd, NULL, GD_OP_REBALANCE);
-                 break;
+                break;
         case GF_DEFRAG_CMD_STOP:
                 /* Clear task-id only on explicitly stopping rebalance.
                  * Also clear the stored operation, so it doesn't cause trouble
diff --git a/xlators/mgmt/glusterd/src/glusterd-utils.c b/xlators/mgmt/glusterd/src/glusterd-utils.c
index 9e8b7c5b650..e93b88ecfdc 100644
--- a/xlators/mgmt/glusterd/src/glusterd-utils.c
+++ b/xlators/mgmt/glusterd/src/glusterd-utils.c
@@ -6233,6 +6233,8 @@ glusterd_restart_rebalance (glusterd_conf_t *conf)
         list_for_each_entry (volinfo, &conf->volumes, vol_list) {
                 if (!volinfo->rebal.defrag_cmd)
                         continue;
+                if (!gd_should_i_start_rebalance (volinfo))
+                        continue;
                 glusterd_volume_defrag_restart (volinfo, op_errstr, 256,
                                         volinfo->rebal.defrag_cmd, NULL);
         }
@@ -7999,3 +8001,66 @@ glusterd_is_status_tasks_op (glusterd_op_t op, dict_t *dict)
 out:
         return is_status_tasks;
 }
+
+/* Tells if rebalance needs to be started for the given volume on the peer
+ *
+ * Rebalance should be started on a peer only if an involved brick is present on
+ * the peer.
+ *
+ * For a normal rebalance, if any one brick of the given volume is present on
+ * the peer, the rebalance process should be started.
+ *
+ * For a rebalance as part of a remove-brick operation, the rebalance process
+ * should be started only if one of the bricks being removed is present on the
+ * peer
+ */
+gf_boolean_t
+gd_should_i_start_rebalance  (glusterd_volinfo_t *volinfo) {
+        gf_boolean_t         retval     = _gf_false;
+        int                  ret        = -1;
+        glusterd_brickinfo_t *brick     = NULL;
+        int                  count      = 0;
+        int                  i          = 0;
+        char                 key[1023]  = {0,};
+        char                 *brickname = NULL;
+
+
+        switch (volinfo->rebal.op) {
+        case GD_OP_REBALANCE:
+                list_for_each_entry (brick, &volinfo->bricks, brick_list) {
+                        if (uuid_compare (MY_UUID, brick->uuid) == 0) {
+                                retval = _gf_true;
+                                break;
+                        }
+                }
+                break;
+        case GD_OP_REMOVE_BRICK:
+                ret = dict_get_int32 (volinfo->rebal.dict, "count", &count);
+                if (ret) {
+                        goto out;
+                }
+                for (i = 1; i <= count; i++) {
+                        memset (key, 0, sizeof (key));
+                        snprintf (key, sizeof (key), "brick%d", i);
+                        ret = dict_get_str (volinfo->rebal.dict, key,
+                                            &brickname);
+                        if (ret)
+                                goto out;
+                        ret = glusterd_volume_brickinfo_get_by_brick (brickname,
+                                                                      volinfo,
+                                                                      &brick);
+                        if (ret)
+                                goto out;
+                        if (uuid_compare (MY_UUID, brick->uuid) == 0) {
+                                retval = _gf_true;
+                                break;
+                        }
+                }
+                break;
+        default:
+                break;
+        }
+
+out:
+        return retval;
+}
diff --git a/xlators/mgmt/glusterd/src/glusterd-utils.h b/xlators/mgmt/glusterd/src/glusterd-utils.h
index 57120fe3942..5b0cfca7b55 100644
--- a/xlators/mgmt/glusterd/src/glusterd-utils.h
+++ b/xlators/mgmt/glusterd/src/glusterd-utils.h
@@ -573,4 +573,7 @@ glusterd_check_gsync_running_local (char *master, char *slave,
 
 gf_boolean_t
 glusterd_is_status_tasks_op (glusterd_op_t op, dict_t *dict);
+
+gf_boolean_t
+gd_should_i_start_rebalance  (glusterd_volinfo_t *volinfo);
 #endif