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

http://blog.csdn.net/jediael_lu/article/details/43854571

http://blog.csdn.net/jediael_lu/article/details/43865571

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 propertieshadoop.log.dir=.hadoop.log.file=hadoop.log# RootLogger - DailyRollingFileAppenderlog4j.rootLogger=INFO,DRFA# Logging Thresholdlog4j.threshold=ALL#special logging requirements for some commandline toolslog4j.logger.org.apache.nutch.crawl.Crawl=INFO,cmdstdoutlog4j.logger.org.apache.nutch.crawl.InjectorJob=INFO,cmdstdoutlog4j.logger.org.apache.nutch.host.HostInjectorJob=INFO,cmdstdoutlog4j.logger.org.apache.nutch.crawl.GeneratorJob=INFO,cmdstdoutlog4j.logger.org.apache.nutch.crawl.DbUpdaterJob=INFO,cmdstdoutlog4j.logger.org.apache.nutch.host.HostDbUpdateJob=INFO,cmdstdoutlog4j.logger.org.apache.nutch.fetcher.FetcherJob=INFO,cmdstdoutlog4j.logger.org.apache.nutch.parse.ParserJob=INFO,cmdstdoutlog4j.logger.org.apache.nutch.indexer.IndexingJob=INFO,cmdstdoutlog4j.logger.org.apache.nutch.indexer.DeleteDuplicates=INFO,cmdstdoutlog4j.logger.org.apache.nutch.indexer.CleaningJob=INFO,cmdstdoutlog4j.logger.org.apache.nutch.crawl.WebTableReader=INFO,cmdstdoutlog4j.logger.org.apache.nutch.host.HostDbReader=INFO,cmdstdoutlog4j.logger.org.apache.nutch.parse.ParserChecker=INFO,cmdstdoutlog4j.logger.org.apache.nutch.indexer.IndexingFiltersChecker=INFO,cmdstdoutlog4j.logger.org.apache.nutch.plugin.PluginRepository=WARNlog4j.logger.org.apache.nutch.api.NutchServer=INFO,cmdstdoutlog4j.logger.org.apache.nutch=INFOlog4j.logger.org.apache.hadoop=WARNlog4j.logger.org.apache.zookeeper=WARNlog4j.logger.org.apache.gora=WARN## Daily Rolling File Appender#log4j.appender.DRFA=org.apache.log4j.DailyRollingFileAppenderlog4j.appender.DRFA.File=${hadoop.log.dir}/${hadoop.log.file}# Rollver at midnightlog4j.appender.DRFA.DatePattern=.yyyy-MM-dd# 30-day backup#log4j.appender.DRFA.MaxBackupIndex=30log4j.appender.DRFA.layout=org.apache.log4j.PatternLayout# Pattern format: Date LogLevel LoggerName LogMessagelog4j.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.ConsoleAppenderlog4j.appender.stdout.layout=org.apache.log4j.PatternLayoutlog4j.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.ConsoleAppenderlog4j.appender.cmdstdout.layout=org.apache.log4j.PatternLayoutlog4j.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