Merge pull request #1568 from cloudant/log-changes-rewind-reasons

Log error when changes forced to rewind to beginning

3 files changed, 24 insertions, 4 deletions

diff --git a/src/couch/src/couch_db.erl b/src/couch/src/couch_db.erl
index 8e932b2ed..55664e964 100644
--- a/src/couch/src/couch_db.erl
+++ b/src/couch/src/couch_db.erl
@@ -1448,9 +1448,17 @@ calculate_start_seq(Db, _Node, {Seq, Uuid, EpochNode}) ->
         true ->
             case is_owner(EpochNode, Seq, get_epochs(Db)) of
                 true -> Seq;
-                false -> 0
+                false ->
+                    couch_log:warning("~p calculate_start_seq not owner "
+                        "db: ~p, seq: ~p, uuid: ~p, epoch_node: ~p, epochs: ~p",
+                        [?MODULE, Db#db.name, Seq, Uuid, EpochNode,
+                            get_epochs(Db)]),
+                    0
             end;
         false ->
+            couch_log:warning("~p calculate_start_seq uuid prefix mismatch "
+                "db: ~p, seq: ~p, uuid: ~p, epoch_node: ~p",
+                [?MODULE, Db#db.name, Seq, Uuid, EpochNode]),
             %% The file was rebuilt, most likely in a different
             %% order, so rewind.
             0
@@ -1882,6 +1890,7 @@ calculate_start_seq_test_() ->
 setup_start_seq() ->
     meck:new(couch_db_engine, [passthrough]),
     meck:expect(couch_db_engine, get_uuid, fun(_) -> <<"foo">> end),
+    ok = meck:expect(couch_log, warning, 2, ok),
     Epochs = [
         {node2, 10},
         {node1, 1}
diff --git a/src/fabric/src/fabric_view_changes.erl b/src/fabric/src/fabric_view_changes.erl
index 37397447b..7288f1aa5 100644
--- a/src/fabric/src/fabric_view_changes.erl
+++ b/src/fabric/src/fabric_view_changes.erl
@@ -456,11 +456,13 @@ do_unpack_seqs(Opaque, DbName) ->
     end.
 
 
-get_old_seq(#shard{range=R}, SinceSeqs) ->
+get_old_seq(#shard{range=R}=Shard, SinceSeqs) ->
     case lists:keyfind(R, 2, SinceSeqs) of
-        {_Node, R, Seq} when is_number(Seq) ->
+        {Node, R, Seq} when is_number(Seq) ->
             % Unfortunately we don't have access to the db
             % uuid so we can't set a replacememnt here.
+            couch_log:warning("~p get_old_seq missing uuid "
+                "node: ~p, range: ~p, seq: ~p", [?MODULE, Node, R, Seq]),
             0;
         {Node, R, {Seq, Uuid}} ->
             % This update seq is using the old format that
@@ -471,7 +473,9 @@ get_old_seq(#shard{range=R}, SinceSeqs) ->
             % This is the newest sequence format that we
             % can use for replacement.
             {Seq, Uuid, EpochNode};
-        _ ->
+        Error ->
+            couch_log:warning("~p get_old_seq error: ~p, shard: ~p, seqs: ~p",
+                [?MODULE, Error, Shard, SinceSeqs]),
             0
     end.
 
diff --git a/src/mem3/src/mem3_rep.erl b/src/mem3/src/mem3_rep.erl
index 03178cf5c..5920f3bd4 100644
--- a/src/mem3/src/mem3_rep.erl
+++ b/src/mem3/src/mem3_rep.erl
@@ -173,6 +173,9 @@ find_source_seq(SrcDb, TgtNode, TgtUUIDPrefix, TgtSeq) ->
         SrcNode = atom_to_binary(node(), utf8),
         find_source_seq_int(Doc, SrcNode, TgtNode, TgtUUID, TgtSeq);
     {not_found, _} ->
+        couch_log:warning("~p find_source_seq repl doc not_found "
+            "src_db: ~p, tgt_node: ~p, tgt_uuid_prefix: ~p, tgt_seq: ~p",
+            [?MODULE, SrcDb, TgtNode, TgtUUIDPrefix, TgtSeq]),
         0
     end.
 
@@ -202,6 +205,10 @@ find_source_seq_int(#doc{body={Props}}, SrcNode0, TgtNode0, TgtUUID, TgtSeq) ->
         [{Entry} | _] ->
             couch_util:get_value(<<"source_seq">>, Entry);
         [] ->
+            couch_log:warning("~p find_source_seq_int nil useable history "
+                "src_node: ~p, tgt_node: ~p, tgt_uuid: ~p, tgt_seq: ~p, "
+                "src_history: ~p",
+                [?MODULE, SrcNode, TgtNode, TgtUUID, TgtSeq, SrcHistory]),
             0
     end.