create f returns a t, given a function that actually performs the final output work. It is the responsibility of the write function to contain all state, and to clean up after itself when it is garbage collected (which may require a finalizer). The function should avoid modifying the contents of the queue; it's reused for each Output.t.

flush should return a deferred that is fulfilled only when all previously written messages are durable (e.g., on disk, out on the network, etc.). It is automatically called by Log on shutdown and at garbage collection. It can be called manually by calling Log.flushed t.

The unit Deferred returned by the function provides an opportunity for pushback if that is important. Only one batch of messages will be "in flight" at any time based on this deferred.

finalize will be called when the output is finalized (meaning, no more open logs use the output, and references to the output are gone).

A version of create that writes without buffering internally and processing in a background loop as outputs usually do, and has access to richer information in the write callback.

filter_to_level wraps an output and gives you a new output which only logs messages which are as/more verbose than level.

This functionality is intended for when you have multiple outputs being displayed in different places, and they need to be at different levels.

If you have one output (or multiple outputs all at the same level), it is better to set the Log.t's output directly with set_level, which is equivalent and more efficient.

• deprecated Do not introduce new uses of this function.