A Xavante or FastCGI instance running an Orbit application can be very long-lived. MySQL has an annoying “feature” that makes it close a connection with a client in case the connection has been idle for a long time, and libmysqlclient has an even more annoying bug where it won’t reopen a dropped connection automatically. Even worse, the error code for a closed connection varies depending on the specific implementation of the server. This used to be a problem for long-lived Orbit applications that kept connections open so they wouldn’t have to be reopened on every request.
Orbit 2.1.0 has a solution to this problem in the form of connections that have timeouts. To create a timed connection you use the orbit.recycle function, passing a connection maker and a timeout in seconds. The function returns a connection proxy that automatically reopens the connection when it becomes stale. For example, if you want a connection that reopens every hour you can do the following, where todo is your Orbit application:
An orthogonal solution to the same problem is also in the new launchers for WSAPI 1.2. If you open wsapi.fcgi this is what you see now (comments were removed for brevity):
The period and ttl properties control the automatic recycling of Lua states by the launcher. After period section the launcher goes through all the states it has allocated, and throws out any state that is older than ttl seconds. So setting ttl to less than the MySQL timeout will guarantee that all your requests will have a connection that has not timed out, as the connection gets reopened when the launcher initializes a new Lua state for your application.
I am open to any suggestions on how to deal with these reliability problems, as I want WSAPI (and, by extension, Orbit) to be reliable without having to sacrifice persistence (and thus performance) too much.