David Pollack, Lift founder, has this to say about sticky sessions and scaling (paragraphs added):
"In practice, scaling a Lift site is much much easier than scaling a LAMP site. Why? Well, state exists someplace. If it exists in the JVM, you get a lot of performance benefits and stability as well as, in Lift's case, lots of security.
Contrast that with sessions in memcached. "Whoop, memcached went down, there go a pile of sessions." "Whoops, we've got a new memcached hashing algorithm, there go all the session." "Whoops, Google just crawled us creating 200,000 new sessions pushing all the but the active sessions out of cache." "Whoops, the Ruby runtime just went wild, ate all the VM on one of our boxes, memcached went down..."
So, you try storing sessions in some wacky shared version of MySQL. This solution requires tons of hardware and a team of make sure that the sharing code is correct, etc. Contrast that to using Nginx, Jetty and session affinity. It's about 4 hours of setup time and it just works. See http://blog.harryh.org/post/7550...
So, talk to a Facebook engineer about the challenges they go through to manage state between the front end, memcached, MySQL, etc. Compare that to Twitter with the famous fail whale. Compare that to Apple's store and the iTunes store which are written on WebObject (which is highly stateful.)
Lift apps running at scale typically require 7% of the front end resources of LAMP app. The Lift apps that are running at scale (Foursquare and Novell pulse are two) do not have the kind of scaling issues associated with LAMP sites that have similar traffic patterns. Scaling with Lift is neither tricky, nor risky. It's simple. It's known. It's proven. Scaling with LAMP is playing whack-a-mole with state and that only becomes a problem at scale."
See his comment under Jackson Davis's answer to this question:
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David Pollack, Lift founder, has this to say about sticky sessions and scaling (paragraphs added):
"In practice, scaling a Lift site is much much easier than scaling a LAMP site. Why? Well, state exists someplace. If it exists in the JVM, you get a lot of performance benefits and stability as well as, in Lift's case, lots of security.
Contrast that with sessions in memcached. "Whoop, memcached went down, there go a pile of sessions." "Whoops, we've got a new memcached hashing algorithm, there go all the session." "Whoops, Google just crawled us creating 200,000 new sessions pushing all the but the active sessions out of cache." "Whoops, the Ruby runtime just went wild, ate all the VM on one of our boxes, memcached went down..."
So, you try storing sessions in some wacky shared version of MySQL. This solution requires tons of hardware and a team of make sure that the sharing code is correct, etc. Contrast that to using Nginx, Jetty and session affinity. It's about 4 hours of setup time and it just works. See http://blog.harryh.org/post/7550...
So, talk to a Facebook engineer about the challenges they go through to manage state between the front end, memcached, MySQL, etc. Compare that to Twitter with the famous fail whale. Compare that to Apple's store and the iTunes store which are written on WebObject (which is highly stateful.)
Lift apps running at scale typically require 7% of the front end resources of LAMP app. The Lift apps that are running at scale (Foursquare and Novell pulse are two) do not have the kind of scaling issues associated with LAMP sites that have similar traffic patterns. Scaling with Lift is neither tricky, nor risky. It's simple. It's known. It's proven. Scaling with LAMP is playing whack-a-mole with state and that only becomes a problem at scale."
See his comment under Jackson Davis's answer to this question:
http://www.quora.com/What-are-the-advantages-and-disadvantag...
Is there any reason why session replication wouldn't work? It works ok on Tomcat (http://tomcat.apache.org/tomcat-6.0-doc/cluster-howto.html) and Jetty has support too.
(I've never use Lift or Scala.)
I don't know, but that would be a good question to pose on Quora, where David seems to frequent.