AsyncLogger: enqueue logging operation instead of a log message

[iRevive]

My attempt to fix #460.

This approach fixes the underlying issue, but it affects the performance as well.

1) AsyncLoggerBenchmark

Original benchmarks of async logger are a little bit of cheating. Since they are basically measuring the queue.offer operation.

Before (master branch):

Benchmark                             Mode  Cnt    Score     Error  Units
AsyncLoggerBenchmark.msg              avgt   25  1241.937 ±  276.487  ns/op
AsyncLoggerBenchmark.msgAndCtx        avgt   25  1274.021 ±   82.916  ns/op
AsyncLoggerBenchmark.msgCtxThrowable  avgt   25  2021.246 ± 1326.558  ns/op

After (fix branch):

Benchmark                             Mode  Cnt    Score     Error  Units
AsyncLoggerBenchmark.msg              avgt   25  699.431 ±  73.839  ns/op
AsyncLoggerBenchmark.msgAndCtx        avgt   25  716.672 ± 105.136  ns/op
AsyncLoggerBenchmark.msgCtxThrowable  avgt   25  926.306 ± 568.412  ns/op

2) Measure the cost of the drain operation

I decided to measure the cost of the drain operation as well. I tweaked AsyncLoggerBenchmark for this purpose:

val (asyncLogger: Logger[IO], cancelToken: IO[Unit]) =
  fileLogger[IO](fileName).withAsync(
+   timeWindow = Int.MaxValue.seconds, // to prevent background flushes
    maxBufferSize = Some(1000000)
  ).allocated.unsafeRunSync()
    
@Benchmark
@OperationsPerInvocation(1000)
def msg(): Unit = 
  (1 to 1000).toList.traverse(_ => asyncLogger.info(message))
+   .flatMap(_ => asyncLogger.drain) 
    .unsafeRunSync()

Before (master branch):

Benchmark                             Mode  Cnt     Score    Error  Units
AsyncLoggerBenchmark.msg              avgt   25  1021.347 ± 32.193  ns/op
AsyncLoggerBenchmark.msgAndCtx        avgt   25  1013.955 ± 68.780  ns/op
AsyncLoggerBenchmark.msgCtxThrowable  avgt   25  4804.478 ± 99.426  ns/op

After (fix branch):

Benchmark                             Mode  Cnt     Score     Error  Units
AsyncLoggerBenchmark.msg              avgt   25  3483.380 ± 125.855  ns/op
AsyncLoggerBenchmark.msgAndCtx        avgt   25  3478.960 ±  95.501  ns/op
AsyncLoggerBenchmark.msgCtxThrowable  avgt   25  7026.014 ± 107.790  ns/op

[codecov]

Codecov Report

Attention: Patch coverage is 91.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.21%. Comparing base (db4444f) to head (9cc6cb5).

Files	Patch %	Lines
...e/src/main/scala/io/odin/loggers/AsyncLogger.scala	91.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #461      +/-   ##
==========================================
+ Coverage   89.16%   89.21%   +0.04%     
==========================================
  Files          35       35              
  Lines         517      519       +2     
  Branches       12        8       -4     
==========================================
+ Hits          461      463       +2     
  Misses         56       56              

Flag	Coverage Δ
unittests	89.21% <91.66%> (+0.04%)	⬆️

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