spark/hbase-spark/src/main/scala/org/apache/hadoop/hbase/spark/Logging.scala

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.hbase.spark

import org.apache.yetus.audience.InterfaceAudience
import org.slf4j.impl.StaticLoggerBinder
import org.slf4j.Logger
import org.slf4j.LoggerFactory

/**
 * Utility trait for classes that want to log data. Creates a SLF4J logger for the class and allows
 * logging messages at different levels using methods that only evaluate parameters lazily if the
 * log level is enabled.
 * Logging is private in Spark 2.0
 * This is to isolate incompatibilties across Spark releases.
 */
@InterfaceAudience.Private
trait Logging {

  // Make the log field transient so that objects with Logging can
  // be serialized and used on another machine
  @transient private var log_ : Logger = null

  // Method to get the logger name for this object
  protected def logName = {
    // Ignore trailing $'s in the class names for Scala objects
    this.getClass.getName.stripSuffix("$")
  }

  // Method to get or create the logger for this object
  protected def log: Logger = {
    if (log_ == null) {
      initializeLogIfNecessary(false)
      log_ = LoggerFactory.getLogger(logName)
    }
    log_
  }

  // Log methods that take only a String
  protected def logInfo(msg: => String) {
    if (log.isInfoEnabled) log.info(msg)
  }

  protected def logDebug(msg: => String) {
    if (log.isDebugEnabled) log.debug(msg)
  }

  protected def logTrace(msg: => String) {
    if (log.isTraceEnabled) log.trace(msg)
  }

  protected def logWarning(msg: => String) {
    if (log.isWarnEnabled) log.warn(msg)
  }

  protected def logError(msg: => String) {
    if (log.isErrorEnabled) log.error(msg)
  }

  // Log methods that take Throwables (Exceptions/Errors) too
  protected def logInfo(msg: => String, throwable: Throwable) {
    if (log.isInfoEnabled) log.info(msg, throwable)
  }

  protected def logDebug(msg: => String, throwable: Throwable) {
    if (log.isDebugEnabled) log.debug(msg, throwable)
  }

  protected def logTrace(msg: => String, throwable: Throwable) {
    if (log.isTraceEnabled) log.trace(msg, throwable)
  }

  protected def logWarning(msg: => String, throwable: Throwable) {
    if (log.isWarnEnabled) log.warn(msg, throwable)
  }

  protected def logError(msg: => String, throwable: Throwable) {
    if (log.isErrorEnabled) log.error(msg, throwable)
  }

  protected def initializeLogIfNecessary(isInterpreter: Boolean): Unit = {
    if (!Logging.initialized) {
      Logging.initLock.synchronized {
        if (!Logging.initialized) {
          initializeLogging(isInterpreter)
        }
      }
    }
  }

  private def initializeLogging(isInterpreter: Boolean): Unit = {
    // Don't use a logger in here, as this is itself occurring during initialization of a logger
    // If Log4j 1.2 is being used, but is not initialized, load a default properties file
    val binderClass = StaticLoggerBinder.getSingleton.getLoggerFactoryClassStr
    Logging.initialized = true

    // Force a call into slf4j to initialize it. Avoids this happening from multiple threads
    // and triggering this: http://mailman.qos.ch/pipermail/slf4j-dev/2010-April/002956.html
    log
  }
}

private object Logging {
  @volatile private var initialized = false
  val initLock = new Object()
}