On 01/08/2012, at 9:14 AM, "Walsh, Peter" <peter.wa...@disney.com> wrote:
> Hello all,
> We have a plugin that uses TSHttpConnect and have noticed that when the
> response is not from cache and is over about 40k, traffic server begins to
> introduce latencies between its callbacks to the event
> TS_EVENT_VCONN_READ_READY. I have only been able to reproduce this in a
> clustered environment, with both 3.0.1 and 3.2. It does not happen in a
> non-clustered environment. Also, when the object is from cache (so no
> chunked encoding), it is returned very fast.
>
> When I turned up debugging I found the following messages "(http_chunk_flow)
> Blocking reenable - flow control in effect" which seem tied to the delays.
It looks like you will get this message in chunked_reenable() when the
following condition is false:
dbuf->max_read_avail() < max_chunked_ahead_bytes &&
dbuf->max_block_count() < max_chunked_ahead_blocks
So max_chunked_ahead_bytes is 32K and max_chunked_ahead_blocks is 128. Maybe if
the origin is fast, ATS can receive the 40K before the client is able to
consume any of it and you end up spuriously activating the flow control.
I don't really have a clue about this part of the code, but that would be my
wild guess. You could try recompiling ATS and bumping max_chunked_ahead_bytes
...
>
> When I try the same call using just a remap rule I have not been able to
> reproduce the issue. That leads me to believe we are doing something wrong
> here with our response handling.
>
> Things I have tried:
>
> * Increasing size to read with TSVConnRead call
> * Increasing proxy.config.io.max_buffer_size
>
> Any help would be greatly appreciated.
>
> Code snippet:
>
> avail = TSIOBufferReaderAvail(mServerResponseBufferReader);
> totalAvail = avail;
> while (avail > 0) {
>
> blk = TSIOBufferReaderStart(mServerResponseBufferReader);
>
> buf_ptr = (char *) TSIOBufferBlockReadStart(blk,
> mServerResponseBufferReader, &read);
> if (read <= 0) {
> break;
> }
> else {
> saveRespData(buf_ptr, read);
> TSIOBufferReaderConsume(mServerResponseBufferReader, read);
> avail -= read;
> }
>
> blk = TSIOBufferBlockNext(blk);
> }
>
> //NOTE: I have tried with and without this statement
> TSVIONDoneSet(mResponseVio, TSVIONDoneGet(mResponseVio) + totalAvail);
>
> TSVIOReenable(mResponseVio);
>
>
> Thank you,
> Pete
