Pull replication no longer works when a source doc has a large attachment
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Key: COUCHDB-679
URL: https://issues.apache.org/jira/browse/COUCHDB-679
Project: CouchDB
Issue Type: Bug
Components: Replication
Environment: trunk and 0.11
Reporter: Filipe Manana
Priority: Blocker
Fix For: 0.11
After rev r916868 (fix for CouchDB-597), doing a pull replication of a doc
that has a large attachment no longer works.
The problem is in couch_rep_att.erl:
convert_stub(#att{data=stub, name=Name} = Attachment,
{#http_db{} = Db, Id, Rev}) ->
{Pos, [RevId|_]} = Rev,
Request = Db#http_db{
resource = lists:flatten([couch_util:url_encode(Id), "/",
couch_util:url_encode(Name)]),
qs = [{rev, couch_doc:rev_to_str({Pos,RevId})}]
},
Ref = make_ref(),
RcvFun = fun() ->
Bin = attachment_receiver(Ref, Request),
cleanup(),
Bin
end,
Attachment#att{data=RcvFun}.
The cleanup/0 function can not be called there, since when the attachment is
received in multiple chunks, after receiving the first chunk the subsequent
ones are silently discarded by cleanup/0:
cleanup() ->
receive
{ibrowse_async_response, _, _} ->
%% TODO maybe log, didn't expect to have data here
cleanup();
{ibrowse_async_response_end, _} ->
cleanup();
{ibrowse_async_headers, _, _, _} ->
cleanup()
after 0 ->
erase(),
ok
end.
If you look into couch_db.erl, you'll see that the attachment receiver function
maybe called multiple times:
flush_att(Fd, #att{data=Fun,att_len=AttLen}=Att) when is_function(Fun) ->
with_stream(Fd, Att, fun(OutputStream) ->
write_streamed_attachment(OutputStream, Fun, AttLen)
end).
write_streamed_attachment(_Stream, _F, 0) ->
ok;
write_streamed_attachment(Stream, F, LenLeft) ->
Bin = F(),
ok = couch_stream:write(Stream, Bin),
write_streamed_attachment(Stream, F, LenLeft - size(Bin)).
This is serious :(
However, removing that call to cleanup/0 may cause the return of CouchDB-597,
therefore I don't supply a patch here.
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