In the end I think the pain of implementing this seamlessly was not worth the gain provided. The intention was that it would allow plain ruby objects that might not live in your main application to be subclassed and have persistence mixed in. But I've decided that the benefit of doing that is not worth the amount of complexity that the implementation introduced.
As a result of different commits, ConnectionPool had become of two minds about exceptions, sometimes using PoolFullError and sometimes using ConnectionTimeoutError. In fact, it was using ConnectionTimeoutError internally, but then recueing and re-raising as a PoolFullError. There's no reason for this bifurcation, standardize on ConnectionTimeoutError, which is the rails2 name and still accurately describes semantics at this point. History In Rails2, ConnectionPool raises a ConnectionTimeoutError if it can't get a connection within timeout. Originally in master/rails3, @tenderlove had planned on removing wait/blocking in connectionpool entirely, at that point he changed exception to PoolFullError. But then later wait/blocking came back, but exception remained PoolFullError. Then in 02b2335 pmahoney introduced fair waiting logic, and brought back ConnectionTimeoutError, introducing the weird bifurcation. ConnectionTimeoutError accurately describes semantics as of this point, and is backwards compat with rails2, there's no reason for PoolFullError to be introduced, and no reason for two different exception types to be used internally, no reason to rescue one and re-raise as another. Unify!
The core of this fix is a threadsafe, fair Queue class. It is very similar to Queue in stdlib except that it supports waiting with a timeout. The issue this solves is that if several threads are contending for database connections, an unfair queue makes is possible that a thread will timeout even while other threads successfully acquire and release connections. A fair queue means the thread that has been waiting the longest will get the next available connection. This includes a few test fixes to avoid test ordering issues that cropped up during development of this patch.
…eouts. #6441 An AR ConnectionSpec `wait_timeout` is pre-patch used for three different things: * mysql2 uses it for MySQL's own wait_timeout (how long MySQL should allow an idle connection before closing it), and defaults to 2592000 seconds. * ConnectionPool uses it for "number of seconds to block and wait for a connection before giving up and raising a timeout error", default 5 seconds. * ConnectionPool uses it for the Reaper, for deciding if a 'dead' connection can be reaped. Default 5 seconds. Previously, if you want to change these from defaults, you need to change them all together. This is problematic _especially_ for the mysql2/ConnectionPool conflict, you will generally _not_ want them to be the same, as evidenced by their wildly different defaults. This has caused real problems for people #6441 #2894 But as long as we're changing this, forcing renaming the ConnectionPool key to be more specific, it made sense to seperate the two ConnectionPool uses too -- these two types of ConnectionPool timeouts ought to be able to be changed independently, you won't neccesarily want them to be the same, even though the defaults are (currently) the same.
…pool" This reverts commit d2901f0, reversing changes made to 525839f. Conflicts: activerecord/test/cases/connection_pool_test.rb Reason: This change broke the build (http://travis-ci.org/#!/rails/rails/builds/1391490) and we don't have any solution until now. I asked the author to try to fix it and open a new pull request.
…oid concurrency error.
…no-op'ing, #reap does the same thing
…on in use for the current thread. fixes #5330
Connection pools are 1:1 with pids.
…ule the watchdog
…ction can be obtained