memcached.sess_consistent_hash Vs. memcached.sess_consistent_hashing

[dterei]

What is the difference between the two and their purpose?

[mhagstrand]

Both options are in the code because of a merge. When pull request #23 was merged into the master branch it added memcached.sess_consistent_hash. I had forked the master branch before then and needed consistent hashing so I added the option and called it memcached.sess_consistent_hashing. When my branch, pull request #38, was merged into master both options where left in php_memcached_session.c.

memcached.sess_consistent_hash sets the behavior MEMCACHED_BEHAVIOR_KETAMA_WEIGHTED.
memcached.sess_consistent_hashing sets the behavior MEMCACHED_BEHAVIOR_KETAMA.

memcached.sess_consistent_hash uses the weighted behavior. This allows you to set a weight in the server list with something like the following in the php.ini:

session.save_path = "10.0.1.1:11211 200,10.0.1.2:11211 100"

As a result about twice as many items will be stored in the server 10.0.1.1:11211 over the 10.0.1.2:11211 server.

When using memcached.sess_consistent_hashing every server is weighted evenly. Each server will store roughly the same number of items.

The code for the memcached.sess_consistent_hashing should probably be removed. It isn't as flexible as memcached.sess_consistent_hash and the code for memcached.sess_consistent_hash is in a better location in my opinion. It is located before the call to status = memcached_server_push(memc_sess->memc_sess, servers);

[dterei]

Great! Thanks for the answer. I may try to submit a pull request then to remove *_hashing when I get the time.