[erlang-questions] yaws 1.97

Claes Wikstrom <>
Sat Oct 19 13:09:53 CEST 2013

Hi all,

We're happy to announce Yaws 1.97

This release contains the usual mix of small improvements, generally
just making Yaws more and more of a rock solid web server.

Code on github,  https://github.com/klacke/yaws
Releases and relnotes on http://yaws.hyber.org

Important DOS note: The OTP file:sendfile is buggy, so all users of
send_file are susceptible to this.  If you use Yaws in production,
carefully ponder the text below.

Christopher Faulet worked this, and his excellent
checkin comment says


Add the way to configure the version of sendfile method to use

Now, at compile time, we only check if sendfile
syscall and file:sendfile/5 are supported. Then,
dynamically, we can configure which version to use.

This can be done using the directive large_file_sendfile.
Supported values are:

      * erlang: if supported, use file:sendfile/5
      * yaws: if supported, use the Yaws sendfile linked-in driver
      * disable: do not use any sendfile method, but gen_tcp:send/2

     If an unsupported method is configured,
     we fall back on gen_tcp:send/2.

     file:sendfile/5 implementation is buggy (in R15 & R16).
     When async-threads are enabled, in efile driver,
     the tcp socket is set in blocking mode and the
     sendfile syscall is executed on an async-thread.
     So an unresponsive client could block it for a very long
     time and therefore block the async-thread.
     In this way, all async-threads could be easily blocked.
     So, by default, the use of sendfile is disable.

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