From d4638836ba2335f5b8eeb4a7624992caf7bb6901 Mon Sep 17 00:00:00 2001
From: Patrick Donnelly <pdonnell@redhat.com>
Date: Thu, 21 Feb 2019 16:34:07 -0800
Subject: [PATCH] fs: obsolete standby_for config options

The operator can no longer configure which rank/fscid/name an MDS wants to
follow or standby for. This was an unfortunately confusing set of config
options as ultimately the MDSMonitor (by default) would set a standby to follow
any fscid/rank if no standby is available that explicitly follows the failed
rank. It is suggested that operators instead use the `standby_count_wanted`
setting on each fs to ensure that sufficient standbys are available.

The temporary effect of this commit is that the MDSMonitor no longer assigns
any standby to standby-replay, to be fixed in the following commits.

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
---
 src/common/legacy_config_opts.h |   5 -
 src/common/options.cc           |  21 ---
 src/mds/Beacon.cc               |   8 --
 src/mds/Beacon.h                |   4 -
 src/mds/FSMap.cc                | 101 +++------------
 src/mds/FSMap.h                 |  35 ++---
 src/mds/MDSMap.cc               |  38 +++---
 src/mds/MDSMap.h                |  27 ++--
 src/mds/MDSRank.cc              |  13 +-
 src/messages/MMDSBeacon.h       |  40 +++---
 src/mon/FSCommands.cc           |   7 +-
 src/mon/MDSMonitor.cc           | 218 +++++---------------------------
 src/mon/MDSMonitor.h            |   5 +-
 13 files changed, 125 insertions(+), 397 deletions(-)

diff --git a/src/common/legacy_config_opts.h b/src/common/legacy_config_opts.h
index 247207e447e..85b43a99d65 100644
--- a/src/common/legacy_config_opts.h
+++ b/src/common/legacy_config_opts.h
@@ -241,7 +241,6 @@ OPTION(mon_allow_pool_delete, OPT_BOOL) // allow pool deletion
 OPTION(mon_fake_pool_delete, OPT_BOOL)  // fake pool deletion (add _DELETED suffix)
 OPTION(mon_globalid_prealloc, OPT_U32)   // how many globalids to prealloc
 OPTION(mon_osd_report_timeout, OPT_INT)    // grace period before declaring unresponsive OSDs dead
-OPTION(mon_force_standby_active, OPT_BOOL) // should mons force standby-replay mds to be active
 OPTION(mon_warn_on_legacy_crush_tunables, OPT_BOOL) // warn if crush tunables are too old (older than mon_min_crush_required_version)
 OPTION(mon_crush_min_required_version, OPT_STR)
 OPTION(mon_warn_on_crush_straw_calc_version_zero, OPT_BOOL) // warn if crush straw_calc_version==0
@@ -475,10 +474,6 @@ OPTION(mds_inject_traceless_reply_probability, OPT_DOUBLE) /* percentage
 OPTION(mds_wipe_sessions, OPT_BOOL)
 OPTION(mds_wipe_ino_prealloc, OPT_BOOL)
 OPTION(mds_skip_ino, OPT_INT)
-OPTION(mds_standby_for_name, OPT_STR)
-OPTION(mds_standby_for_rank, OPT_INT)
-OPTION(mds_standby_for_fscid, OPT_INT)
-OPTION(mds_standby_replay, OPT_BOOL)
 OPTION(mds_enable_op_tracker, OPT_BOOL) // enable/disable MDS op tracking
 OPTION(mds_op_history_size, OPT_U32)    // Max number of completed ops to track
 OPTION(mds_op_history_duration, OPT_U32) // Oldest completed op to track
diff --git a/src/common/options.cc b/src/common/options.cc
index d5fc6d89909..0e5880cc2ff 100644
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -1593,11 +1593,6 @@ std::vector<Option> get_global_options() {
     .add_service("mon")
     .set_description("time before OSDs who do not report to the mons are marked down (seconds)"),
 
-    Option("mon_force_standby_active", Option::TYPE_BOOL, Option::LEVEL_ADVANCED)
-    .set_default(true)
-    .add_service("mon")
-    .set_description("allow use of MDS daemons in standby-replay as replacements"),
-
     Option("mon_warn_on_msgr2_not_enabled", Option::TYPE_BOOL, Option::LEVEL_ADVANCED)
     .set_default(true)
     .add_service("mon")
@@ -7725,22 +7720,6 @@ std::vector<Option> get_mds_options() {
     .set_default(0)
     .set_description(""),
 
-    Option("mds_standby_for_name", Option::TYPE_STR, Option::LEVEL_ADVANCED)
-    .set_default("")
-    .set_description("standby for named MDS daemon when not active"),
-
-    Option("mds_standby_for_rank", Option::TYPE_INT, Option::LEVEL_BASIC)
-    .set_default(-1)
-    .set_description("allow MDS to become a standby:replay daemon"),
-
-    Option("mds_standby_for_fscid", Option::TYPE_INT, Option::LEVEL_ADVANCED)
-    .set_default(-1)
-    .set_description("standby only for the file system with the given fscid"),
-
-    Option("mds_standby_replay", Option::TYPE_BOOL, Option::LEVEL_BASIC)
-    .set_default(false)
-    .set_description("allow MDS to standby replay for an active MDS"),
-
     Option("mds_enable_op_tracker", Option::TYPE_BOOL, Option::LEVEL_ADVANCED)
     .set_default(true)
     .set_description("track remote operation progression and statistics"),
diff --git a/src/mds/Beacon.cc b/src/mds/Beacon.cc
index 07330520c50..8cca7864a31 100644
--- a/src/mds/Beacon.cc
+++ b/src/mds/Beacon.cc
@@ -65,10 +65,6 @@ void Beacon::init(const MDSMap &mdsmap)
   std::unique_lock lock(mutex);
 
   _notify_mdsmap(mdsmap);
-  standby_for_rank = mds_rank_t(g_conf()->mds_standby_for_rank);
-  standby_for_name = g_conf()->mds_standby_for_name;
-  standby_for_fscid = fs_cluster_id_t(g_conf()->mds_standby_for_fscid);
-  standby_replay = g_conf()->mds_standby_replay;
 
   sender = std::thread([this]() {
     std::unique_lock<std::mutex> lock(mutex);
@@ -208,10 +204,6 @@ bool Beacon::_send()
       last_seq,
       CEPH_FEATURES_SUPPORTED_DEFAULT);
 
-  beacon->set_standby_for_rank(standby_for_rank);
-  beacon->set_standby_for_name(standby_for_name);
-  beacon->set_standby_for_fscid(standby_for_fscid);
-  beacon->set_standby_replay(standby_replay);
   beacon->set_health(health);
   beacon->set_compat(compat);
   // piggyback the sys info on beacon msg
diff --git a/src/mds/Beacon.h b/src/mds/Beacon.h
index 768ef556bd4..0116335b6dd 100644
--- a/src/mds/Beacon.h
+++ b/src/mds/Beacon.h
@@ -98,10 +98,6 @@ private:
   std::string name;
   version_t epoch = 0;
   CompatSet compat;
-  mds_rank_t standby_for_rank = MDS_RANK_NONE;
-  std::string standby_for_name;
-  fs_cluster_id_t standby_for_fscid = FS_CLUSTER_ID_NONE;
-  bool standby_replay = false;
   MDSMap::DaemonState want_state = MDSMap::STATE_BOOT;
 
   // Internal beacon state
diff --git a/src/mds/FSMap.cc b/src/mds/FSMap.cc
index 62cfee23cc4..74a340fc700 100644
--- a/src/mds/FSMap.cc
+++ b/src/mds/FSMap.cc
@@ -383,8 +383,7 @@ void FSMap::get_health_checks(health_check_map_t *checks) const
     std::set<mds_rank_t> stuck_failed;
 
     for (const auto &rank : fs->mds_map.failed) {
-      const mds_gid_t replacement = find_replacement_for(
-          {fs->fscid, rank}, {}, g_conf()->mon_force_standby_active);
+      auto&& replacement = find_replacement_for({fs->fscid, rank}, {});
       if (replacement == MDS_GID_NONE) {
         stuck_failed.insert(rank);
       }
@@ -598,22 +597,20 @@ void FSMap::decode(bufferlist::const_iterator& p)
 
       // Construct mds_roles, standby_daemons, and remove
       // standbys from the MDSMap in the Filesystem.
-      for (auto &p : migrate_fs->mds_map.mds_info) {
-        if (p.second.state == MDSMap::STATE_STANDBY_REPLAY) {
-          // In legacy MDSMap, standby replay daemons don't have
-          // rank set, but since FSMap they do.
-          p.second.rank = p.second.standby_for_rank;
-        }
-        if (p.second.rank == MDS_RANK_NONE) {
-          if (p.second.state != MDSMap::STATE_STANDBY) {
+      for (const auto& [gid, info] : migrate_fs->mds_map.mds_info) {
+        if (info.state == MDSMap::STATE_STANDBY_REPLAY) {
+          /* drop any legacy standby-replay daemons */
+          drop_gids.insert(gid);
+        } else if (info.rank == MDS_RANK_NONE) {
+          if (info.state != MDSMap::STATE_STANDBY) {
             // Old MDSMaps can have down:dne here, which
             // is invalid in an FSMap (#17837)
-            drop_gids.insert(p.first);
+            drop_gids.insert(gid);
           } else {
-            insert(p.second); // into standby_daemons
+            insert(info); // into standby_daemons
           }
         } else {
-          mds_roles[p.first] = migrate_fs->fscid;
+          mds_roles[gid] = migrate_fs->fscid;
         }
       }
       for (const auto &p : standby_daemons) {
@@ -714,90 +711,32 @@ void Filesystem::print(std::ostream &out) const
   mds_map.print(out);
 }
 
-mds_gid_t FSMap::find_standby_for(mds_role_t role, std::string_view name) const
+mds_gid_t FSMap::find_replacement_for(mds_role_t role, std::string_view name) const
 {
-  mds_gid_t result = MDS_GID_NONE;
+  auto&& fs = get_filesystem(role.fscid);
 
   // First see if we have a STANDBY_REPLAY
-  auto fs = get_filesystem(role.fscid);
-  for (const auto &i : fs->mds_map.mds_info) {
-    const auto &info = i.second;
+  for (const auto& [gid, info] : fs->mds_map.mds_info) {
     if (info.rank == role.rank && info.state == MDSMap::STATE_STANDBY_REPLAY) {
-      return info.global_id;
+      return gid;
     }
   }
 
   // See if there are any STANDBY daemons available
-  for (const auto &i : standby_daemons) {
-    const auto &gid = i.first;
-    const auto &info = i.second;
-    ceph_assert(info.state == MDSMap::STATE_STANDBY);
+  for (const auto& [gid, info] : standby_daemons) {
     ceph_assert(info.rank == MDS_RANK_NONE);
+    ceph_assert(info.state == MDSMap::STATE_STANDBY);
 
     if (info.laggy()) {
       continue;
     }
 
-    // The mds_info_t may or may not tell us exactly which filesystem
-    // the standby_for_rank refers to: lookup via legacy_client_fscid
-    mds_role_t target_role = {
-      info.standby_for_fscid == FS_CLUSTER_ID_NONE ?
-        legacy_client_fscid : info.standby_for_fscid,
-      info.standby_for_rank};
-
-    if ((target_role.rank == role.rank && target_role.fscid == role.fscid)
-        || (name.length() && info.standby_for_name == name)) {
-      // It's a named standby for *me*, use it.
-      return gid;
-    } else if (
-        info.standby_for_rank < 0 && info.standby_for_name.length() == 0 &&
-        (info.standby_for_fscid == FS_CLUSTER_ID_NONE ||
-         info.standby_for_fscid == role.fscid)) {
-        // It's not a named standby for anyone, use it if we don't find
-        // a named standby for me later, unless it targets another FSCID.
-        result = gid;
-      }
+    return gid;
   }
 
-  return result;
-}
-
-mds_gid_t FSMap::find_unused_for(mds_role_t role,
-				 bool force_standby_active) const {
-  for (const auto &i : standby_daemons) {
-    const auto &gid = i.first;
-    const auto &info = i.second;
-    ceph_assert(info.state == MDSMap::STATE_STANDBY);
-
-    if (info.laggy() || info.rank >= 0)
-      continue;
-
-    if (info.standby_for_fscid != FS_CLUSTER_ID_NONE &&
-        info.standby_for_fscid != role.fscid)
-      continue;
-    if (info.standby_for_rank != MDS_RANK_NONE &&
-        info.standby_for_rank != role.rank)
-      continue;
-
-    // To be considered 'unused' a daemon must either not
-    // be selected for standby-replay or the force_standby_active
-    // setting must be enabled to use replay daemons anyway.
-    if (!info.standby_replay || force_standby_active) {
-      return gid;
-    }
-  }
   return MDS_GID_NONE;
 }
 
-mds_gid_t FSMap::find_replacement_for(mds_role_t role, std::string_view name,
-                               bool force_standby_active) const {
-  const mds_gid_t standby = find_standby_for(role, name);
-  if (standby)
-    return standby;
-  else
-    return find_unused_for(role, force_standby_active);
-}
-
 void FSMap::sanity() const
 {
   if (legacy_client_fscid != FS_CLUSTER_ID_NONE) {
@@ -854,7 +793,7 @@ void FSMap::sanity() const
 
 void FSMap::promote(
     mds_gid_t standby_gid,
-    const Filesystem::ref& filesystem,
+    Filesystem& filesystem,
     mds_rank_t assigned_rank)
 {
   ceph_assert(gid_exists(standby_gid));
@@ -864,7 +803,7 @@ void FSMap::promote(
     ceph_assert(standby_daemons.at(standby_gid).state == MDSMap::STATE_STANDBY);
   }
 
-  MDSMap &mds_map = filesystem->mds_map;
+  MDSMap &mds_map = filesystem.mds_map;
 
   // Insert daemon state to Filesystem
   if (!is_standby_replay) {
@@ -889,7 +828,7 @@ void FSMap::promote(
   }
   info.rank = assigned_rank;
   info.inc = epoch;
-  mds_roles[standby_gid] = filesystem->fscid;
+  mds_roles[standby_gid] = filesystem.fscid;
 
   // Update the rank state in Filesystem
   mds_map.in.insert(assigned_rank);
diff --git a/src/mds/FSMap.h b/src/mds/FSMap.h
index e955f8c422f..46f445ff4fe 100644
--- a/src/mds/FSMap.h
+++ b/src/mds/FSMap.h
@@ -265,7 +265,7 @@ public:
    */
   void promote(
       mds_gid_t standby_gid,
-      const Filesystem::ref& filesystem,
+      Filesystem& filesystem,
       mds_rank_t assigned_rank);
 
   /**
@@ -325,11 +325,9 @@ public:
    * Mutator helper for Filesystem objects: expose a non-const
    * Filesystem pointer to `fn` and update epochs appropriately.
    */
-  void modify_filesystem(
-      const fs_cluster_id_t fscid,
-      std::function<void(Filesystem::ref)> fn)
+  void modify_filesystem(fs_cluster_id_t fscid, auto&& fn)
   {
-    auto fs = filesystems.at(fscid);
+    auto& fs = filesystems.at(fscid);
     fn(fs);
     fs->mds_map.epoch = epoch;
   }
@@ -338,20 +336,18 @@ public:
    * Apply a mutation to the mds_info_t structure for a particular
    * daemon (identified by GID), and make appropriate updates to epochs.
    */
-  void modify_daemon(
-      mds_gid_t who,
-      std::function<void(MDSMap::mds_info_t *info)> fn)
+  void modify_daemon(mds_gid_t who, auto&& fn)
   {
-    if (mds_roles.at(who) == FS_CLUSTER_ID_NONE) {
-      auto &info = standby_daemons.at(who);
-      fn(&info);
+    const auto& fscid = mds_roles.at(who);
+    if (fscid == FS_CLUSTER_ID_NONE) {
+      auto& info = standby_daemons.at(who);
+      fn(info);
       ceph_assert(info.state == MDSMap::STATE_STANDBY);
       standby_epochs[who] = epoch;
     } else {
-      const auto &fs = filesystems[mds_roles.at(who)];
-      auto &info = fs->mds_map.mds_info.at(who);
-      fn(&info);
-
+      auto& fs = filesystems.at(fscid);
+      auto& info = fs->mds_map.mds_info.at(who);
+      fn(info);
       fs->mds_map.epoch = epoch;
     }
   }
@@ -404,7 +400,7 @@ public:
   void update_export_targets(mds_gid_t who, const std::set<mds_rank_t> &targets)
   {
     auto fscid = mds_roles.at(who);
-    modify_filesystem(fscid, [who, &targets](auto fs) {
+    modify_filesystem(fscid, [who, &targets](auto&& fs) {
       fs->mds_map.mds_info.at(who).export_targets = targets;
     });
   }
@@ -458,12 +454,7 @@ public:
     return false;
   }
 
-  mds_gid_t find_standby_for(mds_role_t mds, std::string_view name) const;
-
-  mds_gid_t find_unused_for(mds_role_t mds, bool force_standby_active) const;
-
-  mds_gid_t find_replacement_for(mds_role_t mds, std::string_view name,
-                                 bool force_standby_active) const;
+  mds_gid_t find_replacement_for(mds_role_t mds, std::string_view name) const;
 
   void get_health(list<pair<health_status_t,std::string> >& summary,
 		  list<pair<health_status_t,std::string> > *detail) const;
diff --git a/src/mds/MDSMap.cc b/src/mds/MDSMap.cc
index 1b277f10501..c29b283570a 100644
--- a/src/mds/MDSMap.cc
+++ b/src/mds/MDSMap.cc
@@ -82,10 +82,6 @@ void MDSMap::mds_info_t::dump(Formatter *f) const
   if (laggy_since != utime_t())
     f->dump_stream("laggy_since") << laggy_since;
   
-  f->dump_int("standby_for_rank", standby_for_rank);
-  f->dump_int("standby_for_fscid", standby_for_fscid);
-  f->dump_string("standby_for_name", standby_for_name);
-  f->dump_bool("standby_replay", standby_replay);
   f->open_array_section("export_targets");
   for (set<mds_rank_t>::iterator p = export_targets.begin();
        p != export_targets.end(); ++p) {
@@ -107,16 +103,6 @@ void MDSMap::mds_info_t::print_summary(ostream &out) const
   if (laggy()) {
     out << " laggy since " << laggy_since;
   }
-  if (standby_for_rank != -1 ||
-      !standby_for_name.empty()) {
-    out << " (standby for";
-    //if (standby_for_rank >= 0)
-      out << " rank " << standby_for_rank;
-    if (!standby_for_name.empty()) {
-      out << " '" << standby_for_name << "'";
-    }
-    out << ")";
-  }
   if (!export_targets.empty()) {
     out << " export_targets=" << export_targets;
   }
@@ -535,12 +521,12 @@ void MDSMap::mds_info_t::encode_versioned(bufferlist& bl, uint64_t features) con
     encode(addrs, bl, features);
   }
   encode(laggy_since, bl);
-  encode(standby_for_rank, bl);
-  encode(standby_for_name, bl);
+  encode(MDS_RANK_NONE, bl); /* standby_for_rank */
+  encode(std::string(), bl); /* standby_for_name */
   encode(export_targets, bl);
   encode(mds_features, bl);
-  encode(standby_for_fscid, bl);
-  encode(standby_replay, bl);
+  encode(FS_CLUSTER_ID_NONE, bl); /* standby_for_fscid */
+  encode(false, bl);
   ENCODE_FINISH(bl);
 }
 
@@ -557,8 +543,8 @@ void MDSMap::mds_info_t::encode_unversioned(bufferlist& bl) const
   encode(state_seq, bl);
   encode(addrs.legacy_addr(), bl, 0);
   encode(laggy_since, bl);
-  encode(standby_for_rank, bl);
-  encode(standby_for_name, bl);
+  encode(MDS_RANK_NONE, bl);
+  encode(std::string(), bl);
   encode(export_targets, bl);
 }
 
@@ -573,16 +559,24 @@ void MDSMap::mds_info_t::decode(bufferlist::const_iterator& bl)
   decode(state_seq, bl);
   decode(addrs, bl);
   decode(laggy_since, bl);
-  decode(standby_for_rank, bl);
-  decode(standby_for_name, bl);
+  {
+    mds_rank_t standby_for_rank;
+    decode(standby_for_rank, bl);
+  }
+  {
+    std::string standby_for_name;
+    decode(standby_for_name, bl);
+  }
   if (struct_v >= 2)
     decode(export_targets, bl);
   if (struct_v >= 5)
     decode(mds_features, bl);
   if (struct_v >= 6) {
+    fs_cluster_id_t standby_for_fscid;
     decode(standby_for_fscid, bl);
   }
   if (struct_v >= 7) {
+    bool standby_replay;
     decode(standby_replay, bl);
   }
   DECODE_FINISH(bl);
diff --git a/src/mds/MDSMap.h b/src/mds/MDSMap.h
index b1527f32f0c..a181a611dc4 100644
--- a/src/mds/MDSMap.h
+++ b/src/mds/MDSMap.h
@@ -108,10 +108,6 @@ public:
     version_t state_seq = 0;
     entity_addrvec_t addrs;
     utime_t laggy_since;
-    mds_rank_t standby_for_rank = MDS_RANK_NONE;
-    std::string standby_for_name;
-    fs_cluster_id_t standby_for_fscid = FS_CLUSTER_ID_NONE;
-    bool standby_replay = false;
     std::set<mds_rank_t> export_targets;
     uint64_t mds_features = 0;
 
@@ -536,13 +532,22 @@ public:
     return is_clientreplay(m) || is_active(m) || is_stopping(m);
   }
 
-  bool is_followable(mds_rank_t m) const {
-    return (is_resolve(m) ||
-	    is_replay(m) ||
-	    is_rejoin(m) ||
-	    is_clientreplay(m) ||
-	    is_active(m) ||
-	    is_stopping(m));
+  bool is_followable(mds_rank_t r) const {
+    bool has_followable_rank = false;
+    for (const auto& p : mds_info) {
+      auto& info = p.second;
+      if (info.rank == r) {
+        if (info.state == STATE_ACTIVE) {
+          has_followable_rank = true;
+        } else {
+          return false;
+        }
+      }
+      if (p.second.state == STATE_STANDBY_REPLAY) {
+        return false;
+      }
+    }
+    return has_followable_rank;
   }
 
   bool is_laggy_gid(mds_gid_t gid) const {
diff --git a/src/mds/MDSRank.cc b/src/mds/MDSRank.cc
index 7c99a76716f..ad4a4e50e80 100644
--- a/src/mds/MDSRank.cc
+++ b/src/mds/MDSRank.cc
@@ -2391,17 +2391,12 @@ void MDSRankDispatcher::handle_mds_map(
     // might not include barriers from the previous incarnation of this MDS)
     set_osd_epoch_barrier(objecter->with_osdmap(
 			    std::mem_fn(&OSDMap::get_epoch)));
-  }
 
-  if (is_active()) {
+    /* Now check if we should hint to the OSD that a read may follow */
     bool found = false;
-    MDSMap::mds_info_t info = mdsmap->get_info(whoami);
-
-    for (map<mds_gid_t,MDSMap::mds_info_t>::const_iterator p = mdsmap->get_mds_info().begin();
-       p != mdsmap->get_mds_info().end();
-       ++p) {
-      if (p->second.state == MDSMap::STATE_STANDBY_REPLAY &&
-	  (p->second.standby_for_rank == whoami ||(info.name.length() && p->second.standby_for_name == info.name))) {
+    for (const auto& p : mdsmap->get_mds_info()) {
+      auto& info = p.second;
+      if (info.state == MDSMap::STATE_STANDBY_REPLAY && info.rank == whoami) {
 	found = true;
 	break;
       }
diff --git a/src/messages/MMDSBeacon.h b/src/messages/MMDSBeacon.h
index f45af265e3a..24922ae3330 100644
--- a/src/messages/MMDSBeacon.h
+++ b/src/messages/MMDSBeacon.h
@@ -194,11 +194,6 @@ private:
   MDSMap::DaemonState state = MDSMap::STATE_NULL;
   version_t seq = 0;
 
-  mds_rank_t      standby_for_rank = MDS_RANK_NONE;
-  string          standby_for_name;
-  fs_cluster_id_t standby_for_fscid = FS_CLUSTER_ID_NONE;
-  bool            standby_replay = false;
-
   CompatSet compat;
 
   MDSHealth health;
@@ -228,10 +223,6 @@ public:
   MDSMap::DaemonState get_state() const { return state; }
   version_t get_seq() const { return seq; }
   std::string_view get_type_name() const override { return "mdsbeacon"; }
-  mds_rank_t get_standby_for_rank() const { return standby_for_rank; }
-  const string& get_standby_for_name() const { return standby_for_name; }
-  const fs_cluster_id_t& get_standby_for_fscid() const { return standby_for_fscid; }
-  bool get_standby_replay() const { return standby_replay; }
   uint64_t get_mds_features() const { return mds_features; }
 
   CompatSet const& get_compat() const { return compat; }
@@ -240,12 +231,6 @@ public:
   MDSHealth const& get_health() const { return health; }
   void set_health(const MDSHealth &h) { health = h; }
 
-  void set_standby_for_rank(mds_rank_t r) { standby_for_rank = r; }
-  void set_standby_for_name(string& n) { standby_for_name = n; }
-  void set_standby_for_name(const char* c) { standby_for_name.assign(c); }
-  void set_standby_for_fscid(fs_cluster_id_t f) { standby_for_fscid = f; }
-  void set_standby_replay(bool r) { standby_replay = r; }
-
   const map<string, string>& get_sys_info() const { return sys_info; }
   void set_sys_info(const map<string, string>& i) { sys_info = i; }
 
@@ -262,16 +247,16 @@ public:
     encode((__u32)state, payload);
     encode(seq, payload);
     encode(name, payload);
-    encode(standby_for_rank, payload);
-    encode(standby_for_name, payload);
+    encode(MDS_RANK_NONE, payload);
+    encode(std::string(), payload);
     encode(compat, payload);
     encode(health, payload);
     if (state == MDSMap::STATE_BOOT) {
       encode(sys_info, payload);
     }
     encode(mds_features, payload);
-    encode(standby_for_fscid, payload);
-    encode(standby_replay, payload);
+    encode(FS_CLUSTER_ID_NONE, payload);
+    encode(false, payload);
   }
   void decode_payload() override {
     using ceph::decode;
@@ -282,23 +267,32 @@ public:
     decode((__u32&)state, p);
     decode(seq, p);
     decode(name, p);
-    decode(standby_for_rank, p);
-    decode(standby_for_name, p);
+    {
+      mds_rank_t standby_for_rank;
+      decode(standby_for_rank, p);
+    }
+    {
+      std::string standby_for_name;
+      decode(standby_for_name, p);
+    }
     decode(compat, p);
     decode(health, p);
     if (state == MDSMap::STATE_BOOT) {
       decode(sys_info, p);
     }
     decode(mds_features, p);
-    decode(standby_for_fscid, p);
+    {
+      fs_cluster_id_t standby_for_fscid;
+      decode(standby_for_fscid, p);
+    }
     if (header.version >= 7) {
+      bool standby_replay;
       decode(standby_replay, p);
     }
 
     if (header.version < 7  && state == MDSMap::STATE_STANDBY_REPLAY) {
       // Old MDS daemons request the state, instead of explicitly
       // advertising that they are configured as a replay daemon.
-      standby_replay = true;
       state = MDSMap::STATE_STANDBY;
     }
   }
diff --git a/src/mon/FSCommands.cc b/src/mon/FSCommands.cc
index 6a8e3b19bfa..65685348f49 100644
--- a/src/mon/FSCommands.cc
+++ b/src/mon/FSCommands.cc
@@ -262,21 +262,20 @@ class FsNewHandler : public FileSystemCommandHandler
     mon->osdmon()->propose_pending();
 
     // All checks passed, go ahead and create.
-    auto fs = fsmap.create_filesystem(fs_name, metadata, data,
+    auto&& fs = fsmap.create_filesystem(fs_name, metadata, data,
         mon->get_quorum_con_features());
 
     ss << "new fs with metadata pool " << metadata << " and data pool " << data;
 
     // assign a standby to rank 0 to avoid health warnings
     std::string _name;
-    mds_gid_t gid = fsmap.find_replacement_for({fs->fscid, 0}, _name,
-        g_conf()->mon_force_standby_active);
+    mds_gid_t gid = fsmap.find_replacement_for({fs->fscid, 0}, _name);
 
     if (gid != MDS_GID_NONE) {
       const auto &info = fsmap.get_info_gid(gid);
       mon->clog->info() << info.human_name() << " assigned to filesystem "
           << fs_name << " as rank 0";
-      fsmap.promote(gid, fs, 0);
+      fsmap.promote(gid, *fs, 0);
     }
 
     return 0;
diff --git a/src/mon/MDSMonitor.cc b/src/mon/MDSMonitor.cc
index 8b978637066..301b49aa80f 100644
--- a/src/mon/MDSMonitor.cc
+++ b/src/mon/MDSMonitor.cc
@@ -604,29 +604,9 @@ bool MDSMonitor::prepare_beacon(MonOpRequestRef op)
       new_info.mds_features = m->get_mds_features();
       new_info.state = MDSMap::STATE_STANDBY;
       new_info.state_seq = seq;
-      new_info.standby_for_rank = m->get_standby_for_rank();
-      new_info.standby_for_name = m->get_standby_for_name();
-      new_info.standby_for_fscid = m->get_standby_for_fscid();
-      new_info.standby_replay = m->get_standby_replay();
       pending.insert(new_info);
     }
 
-    // Resolve standby_for_name to a rank
-    const MDSMap::mds_info_t &info = pending.get_info_gid(gid);
-    if (!info.standby_for_name.empty()) {
-      const MDSMap::mds_info_t *leaderinfo = pending.find_by_name(
-          info.standby_for_name);
-      if (leaderinfo && (leaderinfo->rank >= 0)) {
-        const auto &fscid = pending.mds_roles.at(leaderinfo->global_id);
-
-        pending.modify_daemon(gid, [fscid, leaderinfo](
-              MDSMap::mds_info_t *info) {
-            info->standby_for_rank = leaderinfo->rank;
-            info->standby_for_fscid = fscid;
-        });
-      }
-    }
-
     // initialize the beacon timer
     auto &beacon = last_beacon[gid];
     beacon.stamp = mono_clock::now();
@@ -669,17 +649,7 @@ bool MDSMonitor::prepare_beacon(MonOpRequestRef op)
       return true;
     }
 
-    const MDSMap::mds_info_t &info = pending.get_info_gid(gid);
-    // Old MDS daemons don't mention that they're standby replay until
-    // after they've sent their boot beacon, so update this field.
-    if (info.standby_replay != m->get_standby_replay()) {
-      pending.modify_daemon(info.global_id, [&m](
-            MDSMap::mds_info_t *i)
-        {
-          i->standby_replay = m->get_standby_replay();
-        });
-    }
-
+    const auto& info = pending.get_info_gid(gid);
     if (info.state == MDSMap::STATE_STOPPING &&
         state != MDSMap::STATE_STOPPING &&
         state != MDSMap::STATE_STOPPED) {
@@ -692,9 +662,9 @@ bool MDSMonitor::prepare_beacon(MonOpRequestRef op)
 
     if (info.laggy()) {
       dout(1) << "prepare_beacon clearing laggy flag on " << addrs << dendl;
-      pending.modify_daemon(info.global_id, [](MDSMap::mds_info_t *info)
+      pending.modify_daemon(info.global_id, [](auto& info)
         {
-          info->clear_laggy();
+          info.clear_laggy();
         }
       );
     }
@@ -702,7 +672,6 @@ bool MDSMonitor::prepare_beacon(MonOpRequestRef op)
     dout(5)  << "prepare_beacon mds." << info.rank
 	     << " " << ceph_mds_state_name(info.state)
 	     << " -> " << ceph_mds_state_name(state)
-	     << "  standby_for_rank=" << m->get_standby_for_rank()
 	     << dendl;
     if (state == MDSMap::STATE_STOPPED) {
       const auto fscid = pending.mds_roles.at(gid);
@@ -793,9 +762,9 @@ bool MDSMonitor::prepare_beacon(MonOpRequestRef op)
 
       // Made it through special cases and validations, record the
       // daemon's reported state to the FSMap.
-      pending.modify_daemon(gid, [state, seq](MDSMap::mds_info_t *info) {
-        info->state = state;
-        info->state_seq = seq;
+      pending.modify_daemon(gid, [state, seq](auto& info) {
+        info.state = state;
+        info.state_seq = seq;
       });
     }
   }
@@ -1317,8 +1286,8 @@ int MDSMonitor::filesystem_command(
       return -EINVAL;
     }
     if (fsmap.gid_exists(gid)) {
-      fsmap.modify_daemon(gid, [state](MDSMap::mds_info_t *info) {
-        info->state = state;
+      fsmap.modify_daemon(gid, [state](auto& info) {
+        info.state = state;
       });
       ss << "set mds gid " << gid << " to state " << state << " "
          << ceph_mds_state_name(state);
@@ -1743,7 +1712,7 @@ int MDSMonitor::print_nodes(Formatter *f)
 bool MDSMonitor::maybe_resize_cluster(FSMap &fsmap, fs_cluster_id_t fscid)
 {
   auto &current_mds_map = get_fsmap().get_filesystem(fscid)->mds_map;
-  auto fs = fsmap.get_filesystem(fscid);
+  auto&& fs = fsmap.get_filesystem(fscid);
   auto &mds_map = fs->mds_map;
 
   int in = mds_map.get_num_in_mds();
@@ -1767,8 +1736,7 @@ bool MDSMonitor::maybe_resize_cluster(FSMap &fsmap, fs_cluster_id_t fscid)
     while (mds_map.is_in(mds)) {
       mds++;
     }
-    mds_gid_t newgid = fsmap.find_replacement_for({fscid, mds},
-                         name, g_conf()->mon_force_standby_active);
+    auto&& newgid = fsmap.find_replacement_for({fscid, mds}, name);
     if (newgid == MDS_GID_NONE) {
       return false;
     }
@@ -1781,7 +1749,7 @@ bool MDSMonitor::maybe_resize_cluster(FSMap &fsmap, fs_cluster_id_t fscid)
                          "filesystem " << mds_map.fs_name << " as rank "
                       << mds << " (now has " << mds_map.get_num_in_mds() + 1
                       << " ranks)";
-    fsmap.promote(newgid, fs, mds);
+    fsmap.promote(newgid, *fs, mds);
     return true;
   } else if (in > max) {
     mds_rank_t target = in - 1;
@@ -1789,10 +1757,10 @@ bool MDSMonitor::maybe_resize_cluster(FSMap &fsmap, fs_cluster_id_t fscid)
     if (mds_map.is_active(target)) {
       dout(1) << "stopping " << target << dendl;
       mon->clog->info() << "stopping " << info.human_name();
-      fsmap.modify_daemon(info.global_id,
-                            [] (MDSMap::mds_info_t *info) {
-                                info->state = MDSMap::STATE_STOPPING;
-                            });
+      auto f = [](auto& info) {
+        info.state = MDSMap::STATE_STOPPING;
+      };
+      fsmap.modify_daemon(info.global_id, f);
       return true;
     } else {
       dout(20) << "skipping stop of " << target << dendl;
@@ -1837,8 +1805,7 @@ void MDSMonitor::maybe_replace_gid(FSMap &fsmap, mds_gid_t gid,
       info.state != MDSMap::STATE_STANDBY_REPLAY &&
       may_replace &&
       !fsmap.get_filesystem(fscid)->mds_map.test_flag(CEPH_MDSMAP_NOT_JOINABLE) &&
-      (sgid = fsmap.find_replacement_for({fscid, info.rank}, info.name,
-                g_conf()->mon_force_standby_active)) != MDS_GID_NONE)
+      (sgid = fsmap.find_replacement_for({fscid, info.rank}, info.name)) != MDS_GID_NONE)
   {
     
     MDSMap::mds_info_t si = fsmap.get_info_gid(sgid);
@@ -1860,8 +1827,8 @@ void MDSMonitor::maybe_replace_gid(FSMap &fsmap, mds_gid_t gid,
     *osd_propose |= fail_mds_gid(fsmap, gid);
 
     // Promote the replacement
-    auto fs = fsmap.filesystems.at(fscid);
-    fsmap.promote(sgid, fs, info.rank);
+    auto&& fs = fsmap.filesystems.at(fscid);
+    fsmap.promote(sgid, *fs, info.rank);
 
     *mds_propose = true;
   } else if ((info.state == MDSMap::STATE_STANDBY_REPLAY ||
@@ -1879,16 +1846,16 @@ void MDSMonitor::maybe_replace_gid(FSMap &fsmap, mds_gid_t gid,
 	       << " mds." << info.rank << "." << info.inc
 	       << " " << ceph_mds_state_name(info.state)
 	       << " laggy" << dendl;
-      fsmap.modify_daemon(info.global_id, [](MDSMap::mds_info_t *info) {
-          info->laggy_since = ceph_clock_now();
+      fsmap.modify_daemon(info.global_id, [](auto& info) {
+          info.laggy_since = ceph_clock_now();
       });
       *mds_propose = true;
   }
 }
 
-bool MDSMonitor::maybe_promote_standby(FSMap &fsmap, std::shared_ptr<Filesystem> &fs)
+bool MDSMonitor::maybe_promote_standby(FSMap &fsmap, Filesystem& fs)
 {
-  if (fs->mds_map.test_flag(CEPH_MDSMAP_NOT_JOINABLE)) {
+  if (fs.mds_map.test_flag(CEPH_MDSMAP_NOT_JOINABLE)) {
     return false;
   }
 
@@ -1896,111 +1863,19 @@ bool MDSMonitor::maybe_promote_standby(FSMap &fsmap, std::shared_ptr<Filesystem>
 
   // have a standby take over?
   set<mds_rank_t> failed;
-  fs->mds_map.get_failed_mds_set(failed);
-  if (!failed.empty()) {
-    set<mds_rank_t>::iterator p = failed.begin();
-    while (p != failed.end()) {
-      mds_rank_t f = *p++;
-      mds_gid_t sgid = fsmap.find_replacement_for({fs->fscid, f}, {},
-          g_conf()->mon_force_standby_active);
-      if (sgid) {
-        const MDSMap::mds_info_t si = fsmap.get_info_gid(sgid);
-        dout(1) << " taking over failed mds." << f << " with " << sgid
-                << "/" << si.name << " " << si.addrs << dendl;
-        mon->clog->info() << "Standby " << si.human_name()
-                          << " assigned to filesystem " << fs->mds_map.fs_name
-                          << " as rank " << f;
-
-        fsmap.promote(sgid, fs, f);
-	do_propose = true;
-      }
-    }
-  } else if (!fs->mds_map.is_degraded()) {
-    // There were no failures to replace, so try using any available standbys
-    // as standby-replay daemons. Don't do this when the cluster is degraded
-    // as a standby-replay daemon may try to read a journal being migrated.
-
-    // Take a copy of the standby GIDs so that we can iterate over
-    // them while perhaps-modifying standby_daemons during the loop
-    // (if we promote anyone they are removed from standby_daemons)
-    std::vector<mds_gid_t> standby_gids;
-    for (const auto &j : fsmap.standby_daemons) {
-      standby_gids.push_back(j.first);
-    }
-
-    for (const auto &gid : standby_gids) {
-      const auto &info = fsmap.standby_daemons.at(gid);
-      ceph_assert(info.state == MDSMap::STATE_STANDBY);
-
-      if (!info.standby_replay) {
-        continue;
-      }
-
-      /*
-       * This mds is standby but has no rank assigned.
-       * See if we can find it somebody to shadow
-       */
-      dout(20) << "gid " << gid << " is standby and following nobody" << dendl;
-      
-      // standby for someone specific?
-      if (info.standby_for_rank >= 0) {
-        // The mds_info_t may or may not tell us exactly which filesystem
-        // the standby_for_rank refers to: lookup via legacy_client_fscid
-        mds_role_t target_role = {
-          info.standby_for_fscid == FS_CLUSTER_ID_NONE ?
-            fsmap.legacy_client_fscid : info.standby_for_fscid,
-          info.standby_for_rank};
-
-        // It is possible that the map contains a standby_for_fscid
-        // that doesn't correspond to an existing filesystem, especially
-        // if we loaded from a version with a bug (#17466)
-        if (info.standby_for_fscid != FS_CLUSTER_ID_NONE
-            && !fsmap.filesystem_exists(info.standby_for_fscid)) {
-          derr << "gid " << gid << " has invalid standby_for_fscid "
-               << info.standby_for_fscid << dendl;
-          continue;
-        }
-
-        // If we managed to resolve a full target role
-        if (target_role.fscid != FS_CLUSTER_ID_NONE) {
-          const auto &fs = fsmap.get_filesystem(target_role.fscid);
-          if (fs->mds_map.is_followable(target_role.rank)) {
-            do_propose |= try_standby_replay(fsmap, info, *fs,
-                fs->mds_map.get_info(target_role.rank));
-          }
-        }
+  fs.mds_map.get_failed_mds_set(failed);
+  for (const auto& rank : failed) {
+    auto&& sgid = fsmap.find_replacement_for({fs.fscid, rank}, {});
+    if (sgid) {
+      auto&& info = fsmap.get_info_gid(sgid);
+      dout(1) << " taking over failed mds." << rank << " with " << sgid
+              << "/" << info.name << " " << info.addrs << dendl;
+      mon->clog->info() << "Standby " << info.human_name()
+                        << " assigned to filesystem " << fs.mds_map.fs_name
+                        << " as rank " << rank;
 
-	continue;
-      }
-
-      // check everyone
-      for (const auto &p : fsmap.filesystems) {
-	if (info.standby_for_fscid != FS_CLUSTER_ID_NONE &&
-	    info.standby_for_fscid != p.first)
-	  continue;
-
-	bool assigned = false;
-        const auto &fs = p.second;
-        const MDSMap &mds_map = fs->mds_map;
-        for (const auto &mds_i : mds_map.mds_info) {
-          const MDSMap::mds_info_t &cand_info = mds_i.second;
-          if (cand_info.rank >= 0 && mds_map.is_followable(cand_info.rank)) {
-            if ((info.standby_for_name.length() && info.standby_for_name != cand_info.name) ||
-                info.standby_for_rank != MDS_RANK_NONE) {
-              continue;   // we're supposed to follow someone else
-            }
-
-            if (try_standby_replay(fsmap, info, *fs, cand_info)) {
-	      assigned = true;
-              break;
-            }
-          }
-        }
-	if (assigned) {
-	  do_propose = true;
-	  break;
-	}
-      }
+      fsmap.promote(sgid, fs, rank);
+      do_propose = true;
     }
   }
 
@@ -2089,7 +1964,7 @@ void MDSMonitor::tick()
   }
 
   for (auto &p : pending.filesystems) {
-    do_propose |= maybe_promote_standby(pending, p.second);
+    do_propose |= maybe_promote_standby(pending, *p.second);
   }
 
   if (do_propose) {
@@ -2097,29 +1972,6 @@ void MDSMonitor::tick()
   }
 }
 
-/**
- * finfo: the would-be follower
- * leader_fs: the Filesystem containing the would-be leader
- * ainfo: the would-be leader
- */
-bool MDSMonitor::try_standby_replay(
-    FSMap &fsmap,
-    const MDSMap::mds_info_t& finfo,
-    const Filesystem &leader_fs,
-    const MDSMap::mds_info_t& ainfo)
-{
-  // someone else already following?
-  if (leader_fs.has_standby_replay(ainfo.global_id)) {
-    dout(20) << " mds." << ainfo.rank << " already has a follower" << dendl;
-    return false;
-  } else {
-    // Assign the new role to the standby
-    dout(10) << "  setting to follow mds rank " << ainfo.rank << dendl;
-    fsmap.assign_standby_replay(finfo.global_id, leader_fs.fscid, ainfo.rank);
-    return true;
-  }
-}
-
 MDSMonitor::MDSMonitor(Monitor *mn, Paxos *p, string service_name)
   : PaxosService(mn, p, service_name)
 {
diff --git a/src/mon/MDSMonitor.h b/src/mon/MDSMonitor.h
index 2f82e8afb0a..87ce40cc022 100644
--- a/src/mon/MDSMonitor.h
+++ b/src/mon/MDSMonitor.h
@@ -104,12 +104,9 @@ class MDSMonitor : public PaxosService, public PaxosFSMap {
   };
   map<mds_gid_t, beacon_info_t> last_beacon;
 
-  bool try_standby_replay(FSMap &fsmap, const MDSMap::mds_info_t& finfo,
-      const Filesystem &leader_fs, const MDSMap::mds_info_t& ainfo);
-
   std::list<std::shared_ptr<FileSystemCommandHandler> > handlers;
 
-  bool maybe_promote_standby(FSMap &fsmap, std::shared_ptr<Filesystem> &fs);
+  bool maybe_promote_standby(FSMap& fsmap, Filesystem& fs);
   bool maybe_resize_cluster(FSMap &fsmap, fs_cluster_id_t fscid);
   void maybe_replace_gid(FSMap &fsmap, mds_gid_t gid,
       const MDSMap::mds_info_t& info, bool *mds_propose, bool *osd_propose);
-- 
2.39.5