Motivation:
Currently FlushConsolidationHandler only consolidates if a read loop is
active for a Channel, otherwise each writeAndFlush(...) call will still
be flushed individually. When these calls are close enough, it can be
beneficial to consolidate them even outside of a read loop.
Modifications:
When we allow a flush to "go through", don't perform it immediately, but
submit it on the channel's executor. Under high pressure, this gives
other writes a chance to enqueue before the task gets executed, and so
we flush multiple writes at once.
Result:
Lower CPU usage and less context switching.
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