On Friday 17 June 2011, Graham Leggett wrote: > We used openssl to make our non blocking event driven stuff work, > and it works really well (once you've properly handled > SSL_ERROR_WANT_READ and SSL_ERROR_WANT_WRITE). There is no reason > I can see that would stop us using openssl to be async in httpd, > we just need to refactor the mod_ssl code to actually do it.
Someone (Paul?) once told me that openssl is not very good when it comes to async access to the session cache (which could need network io if using memcached), CRLs (which I could imagine to reside in LDAP) and similar things. But this would have to be evaluated. > The tricky part with event driven code is the really bad support > for event driven file access. We used libev as our core event > loop, which does a significant amount of work to make files and > sockets work the same way in the event loop as best it can in a > portable way. Don't know of any other event loop that does this. > It's difficult trying to do the event driven thing if you > intersperse event driven socket handling with blocking file > handling, you end up with many requests blocked by an unrelated > system call. Yes, I guess we would need a pool of lightweight worker threads that does the file io (especially sendfile). Those threads would probably get by with very small stack sizes and use little resources. If the event library we choose already has this built in, we can of course use that, too.
