GCD Background Timers
Coalesce is good for periodic maintenance tasks. You can call the timer many times, and it will fire periodically as needed. By passing different delays into the timer, you can handle events with varying urgency. For example, if you write some very low-priority data to a file handle, you might specify a 60-second delay. If you write high-priority data, you might specify a 0.1-second delay.
MABGTimerwill intelligently combine those so that high-priority data following low-priority data will flush the entire cache.
