[couchdb] branch master updated: Fix epoch mismatch errors (#2027)

[wo...@apache.org]

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wohali pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/couchdb.git


The following commit(s) were added to refs/heads/master by this push:
     new a4145c2  Fix epoch mismatch errors (#2027)
a4145c2 is described below

commit a4145c2947d6b6c7e29757e2e477dc81dc53702d
Author: Paul J. Davis <pa...@gmail.com>
AuthorDate: Tue May 7 15:06:06 2019 -0500

    Fix epoch mismatch errors (#2027)
    
    Originally we posited that duplicate UUIDs could never be created.
    However due to operations interventions its possible to unintentionally
    copy UUIDs in ways that violate this assumption. Instead of crashing the
    process we just reset the seq to zero and log a warning as was done in
    the other instances when we have mismatches in the epoch history.
---
 src/couch/src/couch_db.erl | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/src/couch/src/couch_db.erl b/src/couch/src/couch_db.erl
index ab38eb8..52c3fbb 100644
--- a/src/couch/src/couch_db.erl
+++ b/src/couch/src/couch_db.erl
@@ -1560,7 +1560,14 @@ calculate_start_seq(Db, _Node, {Seq, Uuid, EpochNode}) ->
 calculate_start_seq(Db, _Node, {replace, OriginalNode, Uuid, Seq}) ->
     case is_prefix(Uuid, couch_db:get_uuid(Db)) of
         true ->
-            start_seq(get_epochs(Db), OriginalNode, Seq);
+            try
+                start_seq(get_epochs(Db), OriginalNode, Seq)
+            catch throw:epoch_mismatch ->
+                couch_log:warning("~p start_seq duplicate uuid on node: ~p "
+                    "db: ~p, seq: ~p, uuid: ~p, epoch_node: ~p",
+                    [?MODULE, node(), Db#db.name, Seq, Uuid, OriginalNode]),
+                0
+            end;
         false ->
             {replace, OriginalNode, Uuid, Seq}
     end.
@@ -1607,8 +1614,8 @@ start_seq([{_, NewSeq}, {OrigNode, _} | _], OrigNode, Seq) when Seq > NewSeq ->
     NewSeq;
 start_seq([_ | Rest], OrigNode, Seq) ->
     start_seq(Rest, OrigNode, Seq);
-start_seq([], OrigNode, Seq) ->
-    erlang:error({epoch_mismatch, OrigNode, Seq}).
+start_seq([], _OrigNode, _Seq) ->
+    throw(epoch_mismatch).
 
 
 fold_docs(Db, UserFun, UserAcc) ->
@@ -1986,7 +1993,8 @@ calculate_start_seq_test_() ->
             t_calculate_start_seq_uuid_mismatch(),
             t_calculate_start_seq_is_owner(),
             t_calculate_start_seq_not_owner(),
-            t_calculate_start_seq_raw()
+            t_calculate_start_seq_raw(),
+            t_calculate_start_seq_epoch_mismatch()
         ]
     }.
 
@@ -2031,6 +2039,14 @@ t_calculate_start_seq_raw() ->
         ?assertEqual(13, Seq)
     end).
 
+t_calculate_start_seq_epoch_mismatch() ->
+    ?_test(begin
+        Db = test_util:fake_db([]),
+        SeqIn = {replace, not_this_node, get_uuid(Db), 42},
+        Seq = calculate_start_seq(Db, node1, SeqIn),
+        ?assertEqual(0, Seq)
+    end).
+
 is_owner_test() ->
     ?assertNot(is_owner(foo, 1, [])),
     ?assertNot(is_owner(foo, 1, [{foo, 1}])),