Can we please, please keep the level of discourse relatively civil, especially on matters on fact?

As Matt said, the mutexes used by Merb are used at bootup and once when things are logged (which doesn’t happen per request).

We’re not diametrically opposed to the idea of mutexing other things. In fact, I would expect us to add a few mutexes to our codebase over time for caches in which a clear performance benefit could be demonstrated (i.e. the savings of the cache exceeds the cost of the mutex over many threads).

The difference I believe Matt was trying to point out was just that Merb was designed to be threadsafe from the beginning, which reduces our need for mutexes as well as increases the likelihood that we haven’t missed something important.

As a side note, I’m curious how you were able to make the Rails dependency code threadsafe.

Again, take it easy We’re all on the same (Ruby) side.

However, I did edit the sentence you highlighted for what I meant was not really clear:

“by default, Merb requests don’t go through any locks”

Let me explain that, the mutex you found in the router is only used once when the routes get prepared/compiled, meaning that requests don’t go through them.

The second mutex in on the memory session which is not Merb’s default session store.

Finally, the last mutex is the only mutex you might have to deal with in your app: the logger. However, by default we are only logging errors in production, meaning that the mutex is only used in case of problems. Normal requests don’t get logged and therefore we don’t synchronize the mutex on every single request.

With all due respect, I have to say I was a bit surprised to see what I consider being an insult from a Rails core member. As a frequent reader of your blog though, I guess I should not take offense

You have no idea what you’re saying, do you ?

merb-core/lib/merb-core/dispatch/router.rb: # Compilation is synchronized by mutex.
merb-core/lib/merb-core/dispatch/router.rb: @compiler_mutex = Mutex.new
merb-core/lib/merb-core/dispatch/router.rb: @compiler_mutex.synchronize do
merb-core/lib/merb-core/dispatch/session/memory.rb: @mutex = Mutex.new
merb-core/lib/merb-core/dispatch/session/memory.rb: @mutex.synchronize {
merb-core/lib/merb-core/dispatch/session/memory.rb: @mutex.synchronize {
merb-core/lib/merb-core/dispatch/session/memory.rb: @mutex.synchronize {
merb-core/lib/merb-core/logger.rb: @@mutex = {}
merb-core/lib/merb-core/logger.rb: @mutex = (@@mutex[@log] ||= Mutex.new)
merb-core/lib/merb-core/logger.rb: @mutex.synchronize do