[couchdb] branch 2.3.x-backport-epoch-fix created (now bd42c85)

[wo...@apache.org]

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wohali pushed a change to branch 2.3.x-backport-epoch-fix
in repository https://gitbox.apache.org/repos/asf/couchdb.git.


      at bd42c85  Fix epoch mismatch errors (#2027)

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     new bd42c85  Fix epoch mismatch errors (#2027)

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[couchdb] 01/01: Fix epoch mismatch errors (#2027)

[wo...@apache.org]

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

wohali pushed a commit to branch 2.3.x-backport-epoch-fix
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit bd42c853f68ef34dacc9fd6034d9c18e40cec2f5
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 0ae164d..2cbc297 100644
--- a/src/couch/src/couch_db.erl
+++ b/src/couch/src/couch_db.erl
@@ -1491,7 +1491,14 @@ 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.
@@ -1538,8 +1545,8 @@ 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) ->
@@ -1917,7 +1924,8 @@ 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()
         ]
     }.
 
@@ -1962,6 +1970,14 @@ 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}])),