netty학습을 위한 logback 설정

Netty를 학습하기 위해서 Debug 레벨로 로그를 보고 싶음.

모든 튜토리얼에서 처음에 나오는 클래스인 ServerBootstrap ( https://git.io/fjeuN ) 를 살펴보면  InternalLoggerFactory 클래스를 이용해서 인스턴스를 획득하는 것을 볼 수 있다. 해당 클래스는 abstract class 이고 다양한 로그 라이브러를 지원하고 있음을 알 수 있다.

그 중에서 slf4j - logback 콤보를 이용하기 위해 아래 디펜던시를 추가한다.

<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>1.2.3</version>
</dependency>

그리고 classpath에 아래와 같은 기본적인 logback.xml 을 설정한다

<?xml version="1.0" encoding="UTF-8" ?>
<configuration>
    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
              <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36}
                     - %msg%n</pattern>
        </encoder>
    </appender>

    <root level="DEBUG">
        <appender-ref ref="console"/>
    </root>
</configuration>

아래와 같은 콘솔 로그를 확인 할 수 있다.

 io.netty.util.internal.logging.InternalLoggerFactory - Using SLF4J as the default logging framework
 io.netty.channel.MultithreadEventLoopGroup - -Dio.netty.eventLoopThreads: 24
 io.netty.util.internal.PlatformDependent0 - -Dio.netty.noUnsafe: false
 io.netty.util.internal.PlatformDependent0 - Java version: 8
 io.netty.util.internal.PlatformDependent0 - sun.misc.Unsafe.theUnsafe: available
 io.netty.util.internal.PlatformDependent0 - sun.misc.Unsafe.copyMemory: available
 io.netty.util.internal.PlatformDependent0 - java.nio.Buffer.address: available
 io.netty.util.internal.PlatformDependent0 - direct buffer constructor: available
 io.netty.util.internal.PlatformDependent0 - java.nio.Bits.unaligned: available, true
 io.netty.util.internal.PlatformDependent0 - jdk.internal.misc.Unsafe.allocateUninitializedArray(int): unavailable prior to Java9
 io.netty.util.internal.PlatformDependent0 - java.nio.DirectByteBuffer.(long, int): available
 io.netty.util.internal.PlatformDependent - sun.misc.Unsafe: available
 io.netty.util.internal.PlatformDependent - -Dio.netty.tmpdir: /var/folders/sr/grtv_wmn3wj092488tqh7slr0000gn/T (java.io.tmpdir)
 io.netty.util.internal.PlatformDependent - -Dio.netty.bitMode: 64 (sun.arch.data.model)
 io.netty.util.internal.PlatformDependent - -Dio.netty.noPreferDirect: false
 io.netty.util.internal.PlatformDependent - -Dio.netty.maxDirectMemory: 3817865216 bytes
 io.netty.util.internal.PlatformDependent - -Dio.netty.uninitializedArrayAllocationThreshold: -1
 io.netty.util.internal.CleanerJava6 - java.nio.ByteBuffer.cleaner(): available
 io.netty.channel.nio.NioEventLoop - -Dio.netty.noKeySetOptimization: false
 io.netty.channel.nio.NioEventLoop - -Dio.netty.selectorAutoRebuildThreshold: 512
 io.netty.util.internal.PlatformDependent - org.jctools-core.MpscChunkedArrayQueue: available
 io.netty.channel.DefaultChannelId - -Dio.netty.processId: 78164 (auto-detected)
 io.netty.util.NetUtil - -Djava.net.preferIPv4Stack: false
 io.netty.util.NetUtil - -Djava.net.preferIPv6Addresses: false
 io.netty.util.NetUtil - Loopback interface: lo0 (lo0, 0:0:0:0:0:0:0:1%lo0)
 io.netty.util.NetUtil - Failed to get SOMAXCONN from sysctl and file /proc/sys/net/core/somaxconn. Default: 128
 io.netty.channel.DefaultChannelId - -Dio.netty.machineId: xx:1c:xx:ff:fe:00:00:09 (auto-detected)
 io.netty.util.ResourceLeakDetector - -Dio.netty.leakDetection.level: simple
 io.netty.util.ResourceLeakDetector - -Dio.netty.leakDetection.maxRecords: 4
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.numHeapArenas: 24
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.numDirectArenas: 24
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.pageSize: 8192
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.maxOrder: 11
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.chunkSize: 16777216
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.tinyCacheSize: 512
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.smallCacheSize: 256
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.normalCacheSize: 64
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.maxCachedBufferCapacity: 32768
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.cacheTrimInterval: 8192
 io.netty.buffer.PooledByteBufAllocator - -Dio.netty.allocator.useCacheForAllThreads: true
 io.netty.buffer.ByteBufUtil - -Dio.netty.allocator.type: pooled
 io.netty.buffer.ByteBufUtil - -Dio.netty.threadLocalDirectBufferSize: 65536
 io.netty.buffer.ByteBufUtil - -Dio.netty.maxThreadLocalCharBufferSize: 16384

1라인 : slf4j 를 로깅 프레임웍으로 쓰고 있는 것을 확인 
2라인 : 내 맥북의 사용가능 CPU가 12개 여서 24 ( https://git.io/fjez0 )

주의) 혹시나 java.lang.ClassNotFoundException: jdk.internal.misc.Unsafe 오류가 보인다면 Netty 4.11 을 사용하고 있는지 확인하고 4.12+ 로 버전 변경 한다 ( https://github.com/netty/netty/issues/6901 )