cluster/dht: Provide option to disable fsync in data migration (#2259)

At the moment dht rebalance doesn't give any option to disable fsync
after data migration. Making this an option would give admins take
responsibility of data in a way that is suitable for their cluster.
Default value is still 'on', so that the behavior is intact for people
who don't care about this.

For example: If the data that is going to be migrated is already backed
up or snapshotted, there is no need for fsync to happen right after
migration which can affect active I/O on the volume from applications.

fixes: #2258
Change-Id: I7a50b8d3a2f270d79920ef306ceb6ba6451150c4
Signed-off-by: Pranith Kumar K <pranith.karampuri@phonepe.com>

4 files changed, 37 insertions, 12 deletions

diff --git a/xlators/cluster/dht/src/dht-common.h b/xlators/cluster/dht/src/dht-common.h
index 712a2e98c4..2bf595175e 100644
--- a/xlators/cluster/dht/src/dht-common.h
+++ b/xlators/cluster/dht/src/dht-common.h
@@ -615,6 +615,8 @@ struct dht_conf {
     gf_boolean_t do_weighting;
 
     gf_boolean_t randomize_by_gfid;
+
+    gf_boolean_t ensure_durability;
 };
 typedef struct dht_conf dht_conf_t;
 
diff --git a/xlators/cluster/dht/src/dht-rebalance.c b/xlators/cluster/dht/src/dht-rebalance.c
index a1cd715f58..c3d60b7d2d 100644
--- a/xlators/cluster/dht/src/dht-rebalance.c
+++ b/xlators/cluster/dht/src/dht-rebalance.c
@@ -1818,19 +1818,23 @@ dht_migrate_file(xlator_t *this, loc_t *loc, xlator_t *cached_subvol,
 
     /* TODO: Sync the locks */
 
-    xdata = dict_new();
-    if (!xdata || dict_set_int8(xdata, "last-fsync", 1)) {
-        gf_log(this->name, GF_LOG_ERROR,
-               "%s: failed to set last-fsync flag on "
-               "%s (%s)",
-               loc->path, hashed_subvol->name, strerror(ENOMEM));
-    }
+    if (conf->ensure_durability) {
+        xdata = dict_new();
+        if (!xdata || dict_set_int8(xdata, "last-fsync", 1)) {
+            gf_log(this->name, GF_LOG_ERROR,
+                   "%s: failed to set last-fsync flag on "
+                   "%s (%s)",
+                   loc->path, hashed_subvol->name, strerror(ENOMEM));
+        }
 
-    ret = syncop_fsync(hashed_subvol, dst_fd, 0, NULL, NULL, xdata, NULL);
-    if (ret) {
-        gf_log(this->name, GF_LOG_WARNING, "%s: failed to fsync on %s (%s)",
-               loc->path, hashed_subvol->name, strerror(-ret));
-        *fop_errno = -ret;
+        ret = syncop_fsync(hashed_subvol, dst_fd, 0, NULL, NULL, xdata, NULL);
+        if (ret) {
+            gf_log(this->name, GF_LOG_WARNING, "%s: failed to fsync on %s (%s)",
+                   loc->path, hashed_subvol->name, strerror(-ret));
+            *fop_errno = -ret;
+            ret = -1;
+            goto out;
+        }
     }
 
     /* Phase 2 - Data-Migration Complete, Housekeeping updates pending */
diff --git a/xlators/cluster/dht/src/dht-shared.c b/xlators/cluster/dht/src/dht-shared.c
index 75356c60a2..4c1f17abf5 100644
--- a/xlators/cluster/dht/src/dht-shared.c
+++ b/xlators/cluster/dht/src/dht-shared.c
@@ -476,6 +476,9 @@ dht_reconfigure(xlator_t *this, dict_t *options)
     GF_OPTION_RECONF("force-migration", conf->force_migration, options, bool,
                      out);
 
+    GF_OPTION_RECONF("ensure-durability", conf->ensure_durability, options,
+                     bool, out);
+
     if (conf->defrag) {
         if (dict_get_str(options, "rebal-throttle", &temp_str) == 0) {
             ret = dht_configure_throttle(this, conf, temp_str);
@@ -748,6 +751,8 @@ dht_init(xlator_t *this)
 
     GF_OPTION_INIT("force-migration", conf->force_migration, bool, err);
 
+    GF_OPTION_INIT("ensure-durability", conf->ensure_durability, bool, err);
+
     if (defrag) {
         defrag->lock_migration_enabled = conf->lock_migration_enabled;
 
@@ -1098,6 +1103,15 @@ struct volume_options dht_options[] = {
      .level = OPT_STATUS_ADVANCED,
      .flags = OPT_FLAG_CLIENT_OPT | OPT_FLAG_SETTABLE | OPT_FLAG_DOC},
 
+    {.key = {"ensure-durability"},
+     .type = GF_OPTION_TYPE_BOOL,
+     .default_value = "on",
+     .description = "If disabled, rebalance will not fsync files after "
+                    "migration",
+     .op_version = {GD_OP_VERSION_10_0},
+     .level = OPT_STATUS_ADVANCED,
+     .flags = OPT_FLAG_CLIENT_OPT | OPT_FLAG_SETTABLE | OPT_FLAG_DOC},
+
     {.key = {NULL}},
 };
 
diff --git a/xlators/mgmt/glusterd/src/glusterd-volume-set.c b/xlators/mgmt/glusterd/src/glusterd-volume-set.c
index bb4ae8c4b3..f598f78725 100644
--- a/xlators/mgmt/glusterd/src/glusterd-volume-set.c
+++ b/xlators/mgmt/glusterd/src/glusterd-volume-set.c
@@ -3103,4 +3103,9 @@ struct volopt_map_entry glusterd_volopt_map[] = {
      .op_version = GD_OP_VERSION_9_0,
      .value = "yes",
      .flags = VOLOPT_FLAG_CLIENT_OPT},
+
+    {.key = "rebalance.ensure-durability",
+     .voltype = "cluster/distribute",
+     .op_version = GD_OP_VERSION_10_0,
+     .flags = VOLOPT_FLAG_CLIENT_OPT},
     {.key = NULL}};