Nutch的日志系统
一、Nutch日志实现方式
1、Nutch使用slf4j作为日志接口，使用log4j作为具体实现。关于二者的基础，请参考
2、在java类文件中，通过以下方式输出日志消息：
（1）获取Logger对象
public static final Logger LOG = LoggerFactory.getLogger(InjectorJob.class);
（2）使用Logger进行输出
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
long start = System.currentTimeMillis();
LOG.info("InjectorJob: starting at " + sdf.format(start));
3、在log4j.properties中定义各个属性
# Define some default values that can be overridden by system properties
Hadoop.log.dir=.
hadoop.log.file=hadoop.log
# RootLogger - DailyRollingFileAppender
log4j.rootLogger=INFO,DRFA
# Logging Threshold
log4j.threshold=ALL
#special logging requirements for some commandline tools
log4j.logger.org.apache.nutch.crawl.Crawl=INFO,cmdstdout
log4j.logger.org.apache.nutch.crawl.InjectorJob=INFO,cmdstdout
log4j.logger.org.apache.nutch.host.HostInjectorJob=INFO,cmdstdout
log4j.logger.org.apache.nutch.crawl.GeneratorJob=INFO,cmdstdout
log4j.logger.org.apache.nutch.crawl.DbUpdaterJob=INFO,cmdstdout
log4j.logger.org.apache.nutch.host.HostDbUpdateJob=INFO,cmdstdout
log4j.logger.org.apache.nutch.fetcher.FetcherJob=INFO,cmdstdout
log4j.logger.org.apache.nutch.parse.ParserJob=INFO,cmdstdout
log4j.logger.org.apache.nutch.indexer.IndexingJob=INFO,cmdstdout
log4j.logger.org.apache.nutch.indexer.DeleteDuplicates=INFO,cmdstdout
log4j.logger.org.apache.nutch.indexer.CleaningJob=INFO,cmdstdout
log4j.logger.org.apache.nutch.crawl.WebTableReader=INFO,cmdstdout
log4j.logger.org.apache.nutch.host.HostDbReader=INFO,cmdstdout
log4j.logger.org.apache.nutch.parse.ParserChecker=INFO,cmdstdout
log4j.logger.org.apache.nutch.indexer.IndexingFiltersChecker=INFO,cmdstdout
log4j.logger.org.apache.nutch.plugin.PluginRepository=WARN
log4j.logger.org.apache.nutch.api.NutchServer=INFO,cmdstdout
log4j.logger.org.apache.nutch=INFO
log4j.logger.org.apache.hadoop=WARN
log4j.logger.org.apache.zookeeper=WARN
log4j.logger.org.apache.gora=WARN
#
# Daily Rolling File Appender
#
log4j.appender.DRFA=org.apache.log4j.DailyRollingFileAppender
log4j.appender.DRFA.File=${hadoop.log.dir}/${hadoop.log.file}
# Rollver at midnight
log4j.appender.DRFA.DatePattern=.yyyy-MM-dd
# 30-day backup
#log4j.appender.DRFA.MaxBackupIndex=30
log4j.appender.DRFA.layout=org.apache.log4j.PatternLayout
# Pattern format: Date LogLevel LoggerName LogMessage
log4j.appender.DRFA.layout.ConversionPattern=%d{ISO8601} %-5p %c{2} - %m%n
# Debugging Pattern format: Date LogLevel LoggerName (FileName:MethodName:LineNo) LogMessage
#log4j.appender.DRFA.layout.ConversionPattern=%d{ISO8601} %-5p %c{2} (%F:%M(%L)) - %m%n
#
# stdout
# Add *stdout* to rootlogger above if you want to use this
#
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{ISO8601} %-5p %c{2} (%F:%M(%L)) - %m%n
#
# plain layout used for commandline tools to output to console
#
log4j.appender.cmdstdout=org.apache.log4j.ConsoleAppender
log4j.appender.cmdstdout.layout=org.apache.log4j.PatternLayout
log4j.appender.cmdstdout.layout.ConversionPattern=%m%n
#
# Rolling File Appender
#
#log4j.appender.RFA=org.apache.log4j.RollingFileAppender
#log4j.appender.RFA.File=${hadoop.log.dir}/${hadoop.log.file}
# Logfile size and and 30-day backups
#log4j.appender.RFA.MaxFileSize=1MB
#log4j.appender.RFA.MaxBackupIndex=30
#log4j.appender.RFA.layout=org.apache.log4j.PatternLayout
#log4j.appender.RFA.layout.ConversionPattern=%d{ISO8601} %-5p %c{2} - %m%n
#log4j.appender.RFA.layout.ConversionPattern=%d{ISO8601} %-5p %c{2} (%F:%M(%L)) - %m%n
二、Nutch日志分析
1、nutch日志输出有2个appender: cmdstdout 与 DRFA。
前者将日志输出至标准输出中，后者将文件输出到每日一个的日志文件中。
2、整个工程的默认日志设置为INFO, DRFA
而nutch自身的日志被重定义为INFO,cmdstdout
hadoop, gora, zookeeper等则重定义为WARN，DRFA, 默认日志为./hadoop.log
Nutch的详细介绍：请点这里
Nutch的下载地址：请点这里