[couchdb] 02/02: Eliminate custodian false positive errors for dbs with N < default N

[va...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

vatamane pushed a commit to branch fix-custodian-hard-coded-dbs
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit d6af5506014e918ac8f3acae90b6929c4f38accd
Author: Nick Vatamaniuc <va...@gmail.com>
AuthorDate: Thu Oct 28 16:54:53 2021 -0400

    Eliminate custodian false positive errors for dbs with N < default N
    
    Previously, dbs with N < cluster default N would pollute logs with critical
    errors regarding not having enough shards. Instead, use each database's
    expected N value to emit custodian reports.
    
    Note: the expected N value is a bit tricky to understand since with shard
    splitting feature, shard ranges are not guaranteed to exactly match for all
    copies. The N value is then defined as the max number of rings which can be
    completed with the given set of shards -- complete the ring once, remove
    participating shards, try again, etc. Lucky for us, that function is already
    written (`mem3_util:calculate_max_n(Shards)` so we are just re-using it.
---
 src/custodian/src/custodian_util.erl | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/custodian/src/custodian_util.erl b/src/custodian/src/custodian_util.erl
index ac46cb1..6d5a560 100644
--- a/src/custodian/src/custodian_util.erl
+++ b/src/custodian/src/custodian_util.erl
@@ -21,7 +21,7 @@
 % Old design doc which should be cleaned up
 -define(CUSTODIAN_ID, <<"_design/custodian">>).
 
--record(state, {live, safe, n, callback, db, acc}).
+-record(state, {live, safe, callback, db, acc}).
 
 %% public functions.
 
@@ -55,10 +55,9 @@ ensure_dbs_exists() ->
 fold_dbs(Acc, Fun) ->
     Safe = maybe_redirect([node() | nodes()]),
     Live = Safe -- maintenance_nodes(Safe),
-    N = cluster_n(),
     {ok, Db} = ensure_dbs_exists(),
     try
-        State0 = #state{live=Live, safe=Safe, n=N, callback=Fun, db=Db, acc=Acc},
+        State0 = #state{live=Live, safe=Safe, callback=Fun, db=Db, acc=Acc},
         {ok, State1} = couch_db:fold_docs(Db, fun fold_dbs1/2, State0, []),
         State1#state.acc
     after
@@ -82,9 +81,9 @@ fold_dbs1(#full_doc_info{id = Id} = FDI, State) ->
 fold_dbs(Id, Shards, State) ->
     IsSafe = fun(#shard{node = N}) -> lists:member(N, State#state.safe) end,
     IsLive = fun(#shard{node = N}) -> lists:member(N, State#state.live) end,
-    TargetN = State#state.n,
     LiveShards = lists:filter(IsLive, Shards),
     SafeShards = lists:filter(IsSafe, Shards),
+    TargetN = mem3_util:calculate_max_n(Shards),
     Acc0 = State#state.acc,
     Acc1 = case mem3_util:calculate_max_n(LiveShards) of
         LiveN when LiveN < TargetN ->