Use separate requests to write design when replicatingflush-design-docs-separately-in-replicator

Design doc writes could fail on the target when replicating with non-admin
credentials. Typically the replicator will skip over them and bump the
`doc_write_failures` counter. However, that relies on the POST request
returning a `200 OK` response. If the authentication scheme is implemented such
that the whole request fails if some docs don't have enough permission to be
written, then the replication job ends up crashing with an ugly exception and
gets stuck retrying forever. In order to accomodate that scanario write _design
docs in their separate requests just like we write attachments.

Fixes: #2415

2 files changed, 23 insertions, 12 deletions

diff --git a/src/couch_replicator/src/couch_replicator_worker.erl b/src/couch_replicator/src/couch_replicator_worker.erl
index 23a4ea107..3d80f5883 100644
--- a/src/couch_replicator/src/couch_replicator_worker.erl
+++ b/src/couch_replicator/src/couch_replicator_worker.erl
@@ -269,16 +269,28 @@ fetch_doc(Source, {Id, Revs, PAs}, DocHandler, Acc) ->
     end.
 
 
-remote_doc_handler({ok, #doc{atts = []} = Doc}, {Parent, _} = Acc) ->
-    ok = gen_server:call(Parent, {batch_doc, Doc}, infinity),
-    {ok, Acc};
-remote_doc_handler({ok, Doc}, {Parent, Target} = Acc) ->
+remote_doc_handler({ok, #doc{id = <<?DESIGN_DOC_PREFIX, _/binary>>} = Doc},
+        Acc) ->
+    % Flush design docs in their own PUT requests to correctly process
+    % authorization failures for design doc updates.
+    couch_log:debug("Worker flushing design doc", []),
+    doc_handler_flush_doc(Doc, Acc);
+remote_doc_handler({ok, #doc{atts = [_ | _]} = Doc}, Acc) ->
     % Immediately flush documents with attachments received from a remote
     % source. The data property of each attachment is a function that starts
     % streaming the attachment data from the remote source, therefore it's
     % convenient to call it ASAP to avoid ibrowse inactivity timeouts.
-    Stats = couch_replicator_stats:new([{docs_read, 1}]),
     couch_log:debug("Worker flushing doc with attachments", []),
+    doc_handler_flush_doc(Doc, Acc);
+remote_doc_handler({ok, #doc{atts = []} = Doc}, {Parent, _} = Acc) ->
+    ok = gen_server:call(Parent, {batch_doc, Doc}, infinity),
+    {ok, Acc};
+remote_doc_handler({{not_found, missing}, _}, _Acc) ->
+    throw(missing_doc).
+
+
+doc_handler_flush_doc(#doc{} = Doc, {Parent, Target} = Acc) ->
+    Stats = couch_replicator_stats:new([{docs_read, 1}]),
     Success = (flush_doc(Target, Doc) =:= ok),
     {Result, Stats2} = case Success of
     true ->
@@ -287,9 +299,7 @@ remote_doc_handler({ok, Doc}, {Parent, Target} = Acc) ->
         {{skip, Acc}, couch_replicator_stats:increment(doc_write_failures, Stats)}
     end,
     ok = gen_server:call(Parent, {add_stats, Stats2}, infinity),
-    Result;
-remote_doc_handler({{not_found, missing}, _}, _Acc) ->
-    throw(missing_doc).
+    Result.
 
 
 spawn_writer(Target, #batch{docs = DocList, size = Size}) ->
diff --git a/src/couch_replicator/test/eunit/couch_replicator_many_leaves_tests.erl b/src/couch_replicator/test/eunit/couch_replicator_many_leaves_tests.erl
index be1bfa344..c7933b472 100644
--- a/src/couch_replicator/test/eunit/couch_replicator_many_leaves_tests.erl
+++ b/src/couch_replicator/test/eunit/couch_replicator_many_leaves_tests.erl
@@ -22,7 +22,8 @@
 
 -define(DOCS_CONFLICTS, [
     {<<"doc1">>, 10},
-    {<<"doc2">>, 100},
+    % use some _design docs as well to test the special handling for them
+    {<<"_design/doc2">>, 100},
     % a number > MaxURLlength (7000) / length(DocRevisionString)
     {<<"doc3">>, 210}
 ]).
@@ -111,13 +112,13 @@ should_add_attachments_to_source({remote, Source}) ->
     should_add_attachments_to_source(Source);
 should_add_attachments_to_source(Source) ->
     {timeout, ?TIMEOUT_EUNIT, ?_test(begin
-        {ok, SourceDb} = couch_db:open_int(Source, []),
+        {ok, SourceDb} = couch_db:open_int(Source, [?ADMIN_CTX]),
         add_attachments(SourceDb, ?NUM_ATTS, ?DOCS_CONFLICTS),
         ok = couch_db:close(SourceDb)
     end)}.
 
 populate_db(DbName) ->
-    {ok, Db} = couch_db:open_int(DbName, []),
+    {ok, Db} = couch_db:open_int(DbName, [?ADMIN_CTX]),
     lists:foreach(
        fun({DocId, NumConflicts}) ->
             Value = <<"0">>,
@@ -125,7 +126,7 @@ populate_db(DbName) ->
                 id = DocId,
                 body = {[ {<<"value">>, Value} ]}
             },
-            {ok, _} = couch_db:update_doc(Db, Doc, []),
+            {ok, _} = couch_db:update_doc(Db, Doc, [?ADMIN_CTX]),
             {ok, _} = add_doc_siblings(Db, DocId, NumConflicts)
         end, ?DOCS_CONFLICTS),
     couch_db:close(Db).