[GitHub] [couchdb] davisp commented on issue #985: _changes since=now doesn't send response headers till the first output

[GitBox <gi...@apache.org>]

davisp commented on issue #985: _changes since=now doesn't send response headers till the first output
URL: https://github.com/apache/couchdb/issues/985#issuecomment-537150907
 
 
   Maybe something like such?
   
   ```diff
   diff --git a/src/chttpd/src/chttpd_db.erl b/src/chttpd/src/chttpd_db.erl
   index c6404b04d..659500558 100644
   --- a/src/chttpd/src/chttpd_db.erl
   +++ b/src/chttpd/src/chttpd_db.erl
   @@ -46,6 +46,7 @@
        mochi,
        prepend = "",
        responding = false,
   +    chunks_sent = 0,
        buffer = [],
        bufsize = 0,
        threshold
   @@ -170,10 +171,10 @@ changes_callback({change, {ChangeProp}=Change}, #cacc{feed = eventsource} = Acc)
        Len = iolist_size(Chunk),
        maybe_flush_changes_feed(Acc, Chunk, Len);
    changes_callback(timeout, #cacc{feed = eventsource} = Acc) ->
   -    #cacc{mochi = Resp} = Acc,
   +    #cacc{mochi = Resp, chunks_sent = ChunksSent} = Acc,
        Chunk = "event: heartbeat\ndata: \n\n",
        {ok, Resp1} = chttpd:send_delayed_chunk(Resp, Chunk),
   -    {ok, Acc#cacc{mochi = Resp1}};
   +    {ok, Acc#cacc{mochi = Resp1, chunks_sent = ChunksSent + 1}};
    changes_callback({stop, _EndSeq}, #cacc{feed = eventsource} = Acc) ->
        #cacc{mochi = Resp, buffer = Buf} = Acc,
        {ok, Resp1} = chttpd:send_delayed_chunk(Resp, Buf),
   @@ -209,14 +210,27 @@ changes_callback({stop, EndSeq, Pending}, Acc) ->
        chttpd:end_delayed_json_response(Resp1);
    
    changes_callback(waiting_for_updates, #cacc{buffer = []} = Acc) ->
   -    {ok, Acc};
   +    #cacc{mochi = Resp, chunks_sent = ChunksSent} = Acc,
   +    case ChunksSent > 0 of
   +        true ->
   +            {ok, Acc};
   +        false ->
   +            {ok, Resp1} = chttpd:send_delayed_chunk(Resp, []),
   +            {ok, Acc#cacc{mochi = Resp1, chunks_sent = 1}}
   +    end;
    changes_callback(waiting_for_updates, Acc) ->
   -    #cacc{buffer = Buf, mochi = Resp} = Acc,
   +    #cacc{buffer = Buf, mochi = Resp, chunks_sent = ChunksSent} = Acc,
        {ok, Resp1} = chttpd:send_delayed_chunk(Resp, Buf),
   -    {ok, Acc#cacc{buffer = [], bufsize = 0, mochi = Resp1}};
   +    {ok, Acc#cacc{
   +        buffer = [],
   +        bufsize = 0,
   +        mochi = Resp1,
   +        chunks_sent = ChunksSent + 1
   +    }};
    changes_callback(timeout, Acc) ->
   -    {ok, Resp1} = chttpd:send_delayed_chunk(Acc#cacc.mochi, "\n"),
   -    {ok, Acc#cacc{mochi = Resp1}};
   +    #cacc{mochi = Resp, chunks_sent = ChunksSent} = Acc,
   +    {ok, Resp1} = chttpd:send_delayed_chunk(Resp, "\n"),
   +    {ok, Acc#cacc{mochi = Resp1, chunks_sent = ChunksSent + 1}};
    changes_callback({error, Reason}, #cacc{mochi = #httpd{}} = Acc) ->
        #cacc{mochi = Req} = Acc,
        chttpd:send_error(Req, Reason);
   @@ -228,9 +242,15 @@ changes_callback({error, Reason}, Acc) ->
    
    maybe_flush_changes_feed(#cacc{bufsize=Size, threshold=Max} = Acc, Data, Len)
             when Size > 0 andalso (Size + Len) > Max ->
   -    #cacc{buffer = Buffer, mochi = Resp} = Acc,
   +    #cacc{buffer = Buffer, mochi = Resp, chunks_sent = ChunksSent} = Acc,
        {ok, R1} = chttpd:send_delayed_chunk(Resp, Buffer),
   -    {ok, Acc#cacc{prepend = ",\r\n", buffer = Data, bufsize=Len, mochi = R1}};
   +    Acc1 = Acc#cacc{
   +        prepend = ",\r\n",
   +        buffer = Data,
   +        bufsize = Len,
   +        mochi = R1,
   +        chunks_sent = ChunksSent + 1
   +    }};
    maybe_flush_changes_feed(Acc0, Data, Len) ->
        #cacc{buffer = Buf, bufsize = Size} = Acc0,
        Acc = Acc0#cacc{
   ```

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