rgw multisite: resharding scales up shard counts 4x faster

in multisite reshard, we need to keep the old index shards around until
other zones finishing syncing from them. we don't want to allow a
bunch of reshards in a row, because we have to duplicate that many
sets of index objects. so we impose a limit of 4 bilog generations (or 3
reshards), and refuse to reshard again until bilog trimming catches up/
trims the oldest generation

under a sustained write workload, a bucket can fill quickly and need
successive reshards. if we have a limit of 3, we should make them count!
so instead of doubling the shard count at each step, multiply by 8
instead when we're in a multisite configuration

Signed-off-by: Casey Bodley <cbodley@redhat.com>

diff --git a/src/rgw/rgw_quota.cc b/src/rgw/rgw_quota.cc
index 2d2cf13f253012be910c5255cee932c6dabb3b08..74c2d5ea8c33ab55ca44b41f7f47e4ba4b172818 100644 (file)
--- a/src/rgw/rgw_quota.cc
+++ b/src/rgw/rgw_quota.cc
@@ -962,15 +962,23 @@ public:
     user_stats_cache.adjust_stats(user, bucket, obj_delta, added_bytes, removed_bytes);
   }
 
-  void check_bucket_shards(const DoutPrefixProvider *dpp, uint64_t max_objs_per_shard, uint64_t num_shards,
-                          uint64_t num_objs, bool& need_resharding, uint32_t *suggested_num_shards) override
+  void check_bucket_shards(const DoutPrefixProvider *dpp, uint64_t max_objs_per_shard,
+                           uint64_t num_shards, uint64_t num_objs, bool is_multisite,
+                           bool& need_resharding, uint32_t *suggested_num_shards) override
   {
     if (num_objs > num_shards * max_objs_per_shard) {
       ldpp_dout(dpp, 0) << __func__ << ": resharding needed: stats.num_objects=" << num_objs
              << " shard max_objects=" <<  max_objs_per_shard * num_shards << dendl;
       need_resharding = true;
       if (suggested_num_shards) {
-        *suggested_num_shards = num_objs * 2 / max_objs_per_shard;
+        uint32_t obj_multiplier = 2;
+        if (is_multisite) {
+          // if we're maintaining bilogs for multisite, reshards are significantly
+          // more expensive. scale up the shard count much faster to minimize the
+          // number of reshard events during a write workload
+          obj_multiplier = 8;
+        }
+        *suggested_num_shards = num_objs * obj_multiplier / max_objs_per_shard;
       }
     } else {
       need_resharding = false;

diff --git a/src/rgw/rgw_quota.h b/src/rgw/rgw_quota.h
index c29bac936d07ec2ef343f20de09ccef6d1c5668f..2a63dab4905383b2fe0a1a72bcd30fab118cc63b 100644 (file)
--- a/src/rgw/rgw_quota.h
+++ b/src/rgw/rgw_quota.h
@@ -107,8 +107,9 @@ public:
                           RGWQuota& quota,
                          uint64_t num_objs, uint64_t size, optional_yield y) = 0;
 
-  virtual void check_bucket_shards(const DoutPrefixProvider *dpp, uint64_t max_objs_per_shard, uint64_t num_shards,
-                                  uint64_t num_objs, bool& need_resharding, uint32_t *suggested_num_shards) = 0;
+  virtual void check_bucket_shards(const DoutPrefixProvider *dpp, uint64_t max_objs_per_shard,
+                                   uint64_t num_shards, uint64_t num_objs, bool is_multisite,
+                                   bool& need_resharding, uint32_t *suggested_num_shards) = 0;
 
   virtual void update_stats(const rgw_user& bucket_owner, rgw_bucket& bucket, int obj_delta, uint64_t added_bytes, uint64_t removed_bytes) = 0;
 

diff --git a/src/rgw/rgw_rados.cc b/src/rgw/rgw_rados.cc
index 9189bec7c22b0824f90fbefbba3d95867306aa7a..a77adf72e3ba577f51a40e82ff7b156ae8ec0706 100644 (file)
--- a/src/rgw/rgw_rados.cc
+++ b/src/rgw/rgw_rados.cc
@@ -9408,8 +9408,12 @@ int RGWRados::check_bucket_shards(const RGWBucketInfo& bucket_info,
   const uint64_t max_objs_per_shard =
     cct->_conf.get_val<uint64_t>("rgw_max_objs_per_shard");
 
+  // TODO: consider per-bucket sync policy here?
+  const bool is_multisite = svc.zone->get_zone().log_data;
+
   quota_handler->check_bucket_shards(dpp, max_objs_per_shard, num_source_shards,
-                                    num_objs, need_resharding, &suggested_num_shards);
+                                    num_objs, is_multisite, need_resharding,
+                                    &suggested_num_shards);
   if (! need_resharding) {
     return 0;
   }