Motivation
This is already done internally for various reasons but it would make
sense i.m.o. as a top level concept: submitting a task to be run on the
event loop which doesn't need to run immediately but must still be
executed in FIFO order relative all other submitted tasks (be those
"lazy" or otherwise).
It's nice to separate this abstract "relaxed" semantic from concrete
implementations - the simplest is to just delegate to existing execute,
but for the main EL impls translates to whether a wakeup is required
after enqueuing.
Having a "global" abstraction also allows for simplification of our
internal use - for example encapsulating more of the common scheduled
future logic within AbstractScheduledEventExecutor.
Modifications
- Introduce public LazyRunnable interface and
AbstractEventExecutor#lazyExecute method (would be nice for this to be
added to EventExecutor interface in netty 5)
- Tweak existing SingleThreadEventExecutor mechanics to support these
- Replace internal use of NonWakeupRunnable (such as for pre-flush
channel writes)
- Uplift scheduling-related hooks into AbstractScheduledEventExecutor,
eliminating intermediate executeScheduledRunnable method
Result
Simpler code, cleaner and more useful/flexible abstractions - cleaner in
that they fully communicate the intent in a more general way, without
implying/exposing/restricting implementation details
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