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>

1 files changed, 16 insertions, 11 deletions

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 {