背景：前几天运维同事通知我服务器磁盘快满了，让我清理一下服务器没用的文件。不看不知道，一看吓一跳，应用的Tomcat日志与log4j日志一直没有做清理，系统上线多久，日志就保留了多久，这些日志占据了系统大量的磁盘空间。为此记录一下如何让日志只保留最近7天
1.Tomcat日志
我们进入Tomcat的conf目录下，其中logging.properties文件是专门用于配置Tomcat日志的。配置方案如下：
# 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
#
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# 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.
handlers = 1catalina.org.apache.juli.FileHandler, 2localhost.org.apache.juli.FileHandler, 3manager.org.apache.juli.FileHandler, 4host-manager.org.apache.juli.FileHandler, java.util.logging.ConsoleHandler
.handlers = 1catalina.org.apache.juli.FileHandler, java.util.logging.ConsoleHandler
############################################################
# Handler specific properties.
# Describes specific configuration info for Handlers.
############################################################
1catalina.org.apache.juli.FileHandler.level = FINE
1catalina.org.apache.juli.FileHandler.directory = ${catalina.base}/logs
1catalina.org.apache.juli.FileHandler.prefix = catalina.
1catalina.org.apache.juli.FileHandler.maxDays = 7
1catalina.org.apache.juli.FileHandler.limit = 5000000000
2localhost.org.apache.juli.FileHandler.level = FINE
2localhost.org.apache.juli.FileHandler.directory = ${catalina.base}/logs
2localhost.org.apache.juli.FileHandler.prefix = localhost.
2localhost.org.apache.juli.FileHandler.maxDays = 7
3manager.org.apache.juli.FileHandler.level = FINE
3manager.org.apache.juli.FileHandler.directory = ${catalina.base}/logs
3manager.org.apache.juli.FileHandler.prefix = manager.
3manager.org.apache.juli.FileHandler.maxDays = 7
4host-manager.org.apache.juli.FileHandler.level = FINE
4host-manager.org.apache.juli.FileHandler.directory = ${catalina.base}/logs
4host-manager.org.apache.juli.FileHandler.prefix = host-manager.
4host-manager.org.apache.juli.FileHandler.maxDays = 7
java.util.logging.ConsoleHandler.level = FINE
java.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter
############################################################
# Facility specific properties.
# Provides extra control for each logger.
############################################################
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].level = INFO
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].handlers = 2localhost.org.apache.juli.FileHandler
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].level = INFO
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].handlers = 3manager.org.apache.juli.FileHandler
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/host-manager].level = INFO
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/host-manager].handlers = 4host-manager.org.apache.juli.FileHandler
# For example, set the org.apache.catalina.util.LifecycleBase logger to log
# each component that extends LifecycleBase changing state:
#org.apache.catalina.util.LifecycleBase.level = FINE
# To see debug messages in TldLocationsCache, uncomment the following line:
#org.apache.jasper.compiler.TldLocationsCache.level = FINE
其中我们可以看到 xxxx.maxDays 这个参数，就是配置日志最大的保留日期，这里我填的是7，就是保留7天。
2.log4j日志
2.1log4j1
这里我查阅了大量的资料和观看源码，最终得出结论：log4j1不支持保留最近7天！，即使你是用上了log4j-extras这个包，也做不到保留最近7天！
log4j1最常用的滚动记录日志方式有两种：org.apache.log4j.RollingFileAppender和org.apache.log4j.DailyRollingFileAppender。
org.apache.log4j.RollingFileAppender是根据文件的大小做日志分割，他有两个参数MaxFileSize和MaxBackupIndex，分别表示文件的大小以及保留文件的数量。输出的文件命名是：ali.log.1、ali.log.2、ali.log.3，输出多少个文件取决于MaxBackupIndex设置多少。这种模式不是按照天数来生成文件的，只要日志的大小到达MaxFileSize的值，就会输出一个日志文件。org.apache.log4j.DailyRollingFileAppender是每天对日志做分割，他有这个参数datePattern，默认值是'.'yyyy-MM-dd，意思是每天输出的文件命名是ali.log.2024-07-17、ali.log.2024-07-18、ali.log.2024-07-19，当然如果你不喜欢这种日期的输出方式，也是可以做更改的。这种模式会每天一直输出一份日志文件，不会停止！
特别注意：以上两种模式的参数，是不能够混合使用的，比如我选择了RollingFileAppender模式，然后又配置了datePattern参数，这样是不行的，即使你这样也配置了，也不会生效！
那如果我的系统用了log4j1这个框架，如何做到日志按日期拆分的同时又能保留最近7天呢？以下两种方法：
1.使用linux的crontab定时任务，每隔一段时间定时做删除
2.将log4j1升级到log4j2，但这种方式需要自行评估升级风险，且log4j1的配置文件与log4j2差异巨大
2.2log4j2
log4j2的配置方式可以参考这篇文章：https://blog.csdn.net/weixin_41979605/article/details/118421323
