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[Bug 14530] New: Hi, In Server-Sent Events Section "Processing model", it should be clearly stated how to avoid the pipelining of HTTP requests on the connection used for an event source. HTTP pipelining - decribed in RFC 2616 / section 8.1.2.2 - is the possibility for a

From: <bugzilla@jessica.w3.org>
Date: Fri, 21 Oct 2011 14:00:18 +0000
To: public-webapps@w3.org
Message-ID: <bug-14530-2927@http.www.w3.org/Bugs/Public/>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=14530

           Summary: Hi, In Server-Sent Events Section "Processing model",
                    it should be clearly stated how to avoid the
                    pipelining of HTTP requests on the connection used for
                    an event source. HTTP pipelining - decribed in RFC
                    2616 / section 8.1.2.2 - is the possibility for a
           Product: WebAppsWG
           Version: unspecified
          Platform: Other
               URL: http://www.whatwg.org/specs/web-apps/current-work/#top
        OS/Version: other
            Status: NEW
          Severity: normal
          Priority: P3
         Component: Server-Sent Events (editor: Ian Hickson)
        AssignedTo: ian@hixie.ch
        ReportedBy: contributor@whatwg.org
         QAContact: member-webapi-cvs@w3.org
                CC: mike@w3.org, public-webapps@w3.org


Specification: http://www.w3.org/TR/eventsource/
Multipage: http://www.whatwg.org/C#top
Complete: http://www.whatwg.org/c#top

Comment:
Hi,

In Server-Sent Events Section "Processing model", it should be clearly stated
how to avoid the pipelining of HTTP requests on the connection used for an
event source.

HTTP pipelining - decribed in RFC 2616 / section 8.1.2.2 - is the possibility
for a user agent to send a new HTTP request on a connection before the HTTP
response of the previous request on the same connection is received.
On a connection used for server-sent events, pipelining new HTTP requests
cause them to hang forever, since the event stream is potentially infinite. 
I had this issue recently and some images in my web app were never loaded.

I see 2 possible solutions for this type of issue (not necessarily exclusive,
of course):
1- it should be clearly stated that a user agent shall not use a connection
with a pending text/eventstream typed request for pipelining
2- The server should set a "Connection: close" HTTP header in the event-stream
response to prevent any reuse of the same connection by the user agent.

This second option solved the issue in my case, but, as I didn't find any
guideline on this subject in the current Server-Sent Events draft, I decided
to send you this feedback.

Hope this can help.

Jean-Luc (jean-luc@comimos.com)

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