<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 TRANSITIONAL//EN">
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; CHARSET=UTF-8">
<META NAME="GENERATOR" CONTENT="GtkHTML/4.2.2">
</HEAD>
<BODY LINK="#0000ff">
Hello Rahul,<BR>
<BR>
Thanks for reporting. I'm reviewing the issue. I'll let you know something,<BR>
<BR>
Best Regards,<BR>
<BR>
<BLOCKQUOTE TYPE=CITE>
<BR>
<BR>
Hello,<BR>
<BR>
<BR>
<BR>
I have some more debug information regarding this issue.<BR>
<BR>
<BR>
<BR>
To confirm the conjecture that the next two bytes may not always be immediately available,<BR>
<BR>
I made a local modification as shown below and ran the test again waiting for next failure. <BR>
<BR>
Instead of immediately aborting the connection when this situation occurs, I poll the connection<BR>
<BR>
for a short duration to see if the next two bytes appear subsequently, and then abort the connection anyway.<BR>
<BR>
<BR>
<BR>
} else if (msg->payload_size == 126) {<BR>
<BR>
/* get extended 2 bytes length as unsigned 16 bit<BR>
<BR>
unsigned integer */<BR>
<BR>
bytes = __nopoll_conn_receive (conn, buffer + 2, 2);<BR>
<BR>
if (bytes != 2) {<BR>
<BR>
int i;<BR>
<BR>
nopoll_log (conn->ctx, NOPOLL_LEVEL_CRITICAL, "Failed to get next 2 bytes to read header from the wire (read %d, %d), failed to received content, shutting down id=%d the connection", bytes, errno, conn->id);<BR>
<BR>
for (i = 0; i < 100; i++) {<BR>
<BR>
bytes = __nopoll_conn_receive (conn, buffer + 2, 2);<BR>
<BR>
if (bytes == 2) {<BR>
<BR>
nopoll_log (conn->ctx, NOPOLL_LEVEL_CRITICAL, "Finally got next 2 bytes to read header from the wire after %d tries, shutting down anyway id=%d the connection", i, conn->id);<BR>
<BR>
break;<BR>
<BR>
}<BR>
<BR>
nopoll_sleep(10); // 10 ms sleep<BR>
<BR>
}<BR>
<BR>
nopoll_msg_unref (msg);<BR>
<BR>
nopoll_conn_shutdown (conn);<BR>
<BR>
return NULL; <BR>
<BR>
} /* end if */<BR>
<BR>
<BR>
<BR>
The above is just a local change to confirm the root cause.<BR>
<BR>
<BR>
<BR>
I reproduced the disconnection bug again and from the logs, you can see that only one byte was available initially<BR>
<BR>
and after a very short duration we do get the remaining bytes.<BR>
<BR>
<BR>
<BR>
The relevant log lines look like:<BR>
<BR>
<BR>
<BR>
nopoll_conn.c:2798 Failed to get next 2 bytes to read header from the wire (read 1, 0), failed to received content, shutting down id=2 the connection <BR>
<BR>
nopoll_conn.c:2802 Finally got next 2 bytes to read header from the wire after 5 tries, shutting down anyway id=2 the connection <BR>
<BR>
<BR>
<BR>
I think, not getting next 2 (or 4 bytes) should not be treated as an error situation, but rather treated as<BR>
<BR>
full message not yet available just like when waiting for the first two bytes of the message. The call is supposed to be<BR>
<BR>
non-blocking so we of course cannot poll like the test code snippet above. <BR>
<BR>
<BR>
<BR>
Do let me know if you need any further info.<BR>
<BR>
This issue is very critical to move forward with our current application.<BR>
<BR>
<BR>
<BR>
Regards,<BR>
<BR>
<BR>
<BR>
Rahul<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
</BLOCKQUOTE>
<BLOCKQUOTE TYPE=CITE>
<B>From:</B> nopoll-bounces@lists.aspl.es [mailto:nopoll-bounces@lists.aspl.es] <B>On Behalf Of </B>Kale, Rahul<BR>
<B>Sent:</B> Tuesday, April 19, 2016 6:33 PM<BR>
<B>To:</B> nopoll@lists.aspl.es<BR>
<B>Subject:</B> [noPoll] Websocket disconnect issues<BR>
<BR>
<BR>
</BLOCKQUOTE>
<BLOCKQUOTE TYPE=CITE>
<BR>
<BR>
<BR>
<BR>
Hello,<BR>
<BR>
<BR>
<BR>
I have been trying to track down a random websocket disconnection issue that we are facing.<BR>
<BR>
In our application, after some random number of hours of a good websocket connection that is <BR>
<BR>
transferring data back and forth, the connection suddenly breaks. We are using noPoll only<BR>
<BR>
for the client side of a WebSocket connection. The server side is Apache frontend with <BR>
<BR>
node app backend.<BR>
<BR>
<BR>
<BR>
After eliminating all other probable causes, I enabled noPoll debug logs and was finally able <BR>
<BR>
to catch the error which causes a disconnect: <BR>
<BR>
<BR>
<BR>
nopoll_conn.c:2797 Failed to get next 2 bytes to read header from the wire, failed to received content, shutting down id=2 the connection <BR>
<BR>
<BR>
<BR>
Reproducing this is difficult since it takes anything from a couple of hours to a couple of days<BR>
<BR>
but eventually it happens. My debugging efforts at narrowing this down is thus taking quite a while.<BR>
<BR>
<BR>
<BR>
We are using secure web sockets (wss://). <BR>
<BR>
<BR>
<BR>
Looking at the code, it seems that in the noPoll library, we expect the next two bytes of <BR>
<BR>
the websocket header to be always available if we read the first two bytes. <BR>
<BR>
I think that over TCP (and possibly even more so over TLS)<BR>
<BR>
this may not always be guaranteed. The socket is non-blocking and it may occasionally<BR>
<BR>
have a pattern that 4 bytes are split over two (or more) TCP segments.<BR>
<BR>
<BR>
<BR>
For reading first two bytes noPoll library seems to be buffering if data is not available.<BR>
<BR>
For correctness, should this be done for subsequent parts of the header too?<BR>
<BR>
Of course, I am not an expert here so could you analyze and let me know what is could<BR>
<BR>
be the root cause? What should be my next steps?<BR>
<BR>
<BR>
<BR>
I have already verified that this is not due to http(s) server error. I did a TCP dump<BR>
<BR>
and confirmed that when this happens, the first FIN is sent by the client (noPoll) to the http server.<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
Regards,<BR>
<BR>
<BR>
<BR>
Rahul<BR>
<BR>
<BR>
<BR>
Rahul Kale<BR>
<BR>
<BR>
<BR>
IP Video Systems<BR>
<BR>
Barco, Inc<BR>
<BR>
1287 Anvilwood Ave<BR>
<BR>
Sunnyvale, CA 94089<BR>
<BR>
<BR>
<BR>
Tel +1 408 400 4238<BR>
<BR>
<BR>
<BR>
This message is subject to the following terms and conditions: <A HREF="http://www.barco.com/en/maildisclaimer">MAIL DISCLAIMER</A> <BR>
<BR>
<BR>
</BLOCKQUOTE>
<BLOCKQUOTE TYPE=CITE>
This message is subject to the following terms and conditions: <A HREF="http://www.barco.com/en/maildisclaimer">MAIL DISCLAIMER</A><BR>
</BLOCKQUOTE>
<BR>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%">
<TR>
<TD>
<PRE>
--
Francis Brosnan Blázquez - ASPL
<A HREF="http://www.asplhosting.com/">http://www.asplhosting.com/</A>
<A HREF="http://www.aspl.es/">http://www.aspl.es/</A>
<A HREF="https://twitter.com/aspl_es">https://twitter.com/aspl_es</A>
<A HREF="https://twitter.com/asplhosting">https://twitter.com/asplhosting</A>
<A HREF="https://twitter.com/francisbrosnanb">https://twitter.com/francisbrosnanb</A>
91 134 14 22 - 91 134 14 45 - 91 116 07 57
AVISO LEGAL
En virtud de lo dispuesto en la Ley Orgánica 15/1999, de 13 de
diciembre, de Protección de Datos de Carácter Personal, le informamos de
que sus datos de carácter personal, recogidos de fuentes accesibles al
público o datos que usted nos ha facilitado previamente, proceden de
bases de datos propiedad de Advanced Software Production Line, S.L.
(ASPL).
ASPL garantiza que los datos serán tratados con la finalidad de mantener
las oportunas relaciones comerciales o promocionales con usted o la
entidad que usted representa. No obstante, usted puede ejercitar sus
derechos de acceso, rectificación, cancelación y oposición dispuestos en
la mencionada Ley Orgánica, notificándolo por escrito a ASPL -
Protección Datos, C/Antonio Suárez 10 A-102, 28802, Alcalá de Henares
(Madrid).
</PRE>
</TD>
</TR>
</TABLE>
</BODY>
</HTML>