4-异常-log4j配置日志滚动覆盖出现日志丢失问题

4-异常-log4j配置日志打印滚动覆盖出现日志丢失问题(附源码分析)

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问题描述：服务经常性的出现某些时刻数据丢失问题。

问题原因：日志配置了同一天日志文件的数量最大值，日志打印的滚动打印配置。所以当日志比较多的时候，超过这个最大数量的日志会滚动覆盖出现日志丢失问题。

解决方案：根据服务具体的日志需求，设置 DefaultRolloverStrategy 标签的 max 属性的值，找出一个比较适合的值。

log4j配置如下：

重点查看 Appenders 里面的 DefaultRolloverStrategy 标签的属性；
DefaultRolloverStrategy 的 max 是配置滚动文件的数量，默认的最大值为 7；

<?xml version="1.0" encoding="UTF-8"?><Configuration status="WARN"><Properties><Property name="baseDir">../logs</Property><Property name="appCode">appCode</Property><Property name="PID">????</Property><Property name="LOG_EXCEPTION_CONVERSION_WORD">%xwEx</Property><Property name="LOG_LEVEL_PATTERN">%5p</Property><Property name="CONSOLE_LOG_PATTERN">%clr{%d{yyyy-MM-dd HH:mm:ss.SSS}}{faint} %clr{${LOG_LEVEL_PATTERN}} %clr{${sys:PID}}{magenta} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%l}{cyan} %clr{:}{faint}%m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property><Property name="FILE_LOG_PATTERN">%d{yyyy-MM-dd HH:mm:ss.SSS} ${LOG_LEVEL_PATTERN} ${sys:PID} --- [%t] %-40.40c{1.} : %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property></Properties><Appenders><Console name="Console" target="SYSTEM_OUT" follow="true"><PatternLayout pattern="${sys:CONSOLE_LOG_PATTERN}"/></Console><RollingFile name="RollingFileInfo" fileName="${baseDir}/${appCode}.log"filePattern="${baseDir}/${appCode}/$${date:yyyy-MM}/${appCode}-%d{yyyy-MM-dd}-%i.log"><!--控制台只输出level及以上级别的信息（onMatch），其他的直接拒绝（onMismatch）--><ThresholdFilter level="info" onMatch="ACCEPT" onMismatch="DENY"/><PatternLayout pattern="[%d{HH:mm:ss:SSS}] [%p] - %l - %m%n"/><Policies><TimeBasedTriggeringPolicy/><SizeBasedTriggeringPolicy size="100 MB"/></Policies><DefaultRolloverStrategy><Delete basePath="${baseDir}" maxDepth="3"><IfFileName glob="${appCode}/*/*.log" /><IfLastModified age="365d" /></Delete></DefaultRolloverStrategy></RollingFile></Appenders><Loggers><logger name="org.springframework" level="debug"/><root level="debug"><AppenderRef ref="Console"/><AppenderRef ref="RollingFileInfo"/></root></Loggers>
</Configuration>

源码如下：

DEFAULT_WINDOW_SIZE = 7
由下列的build()方法可知，创建时假若没有设置 max 的值，则使用 DEFAULT_WINDOW_SIZE 的值，这个值为 7；

@Plugin(name = "DefaultRolloverStrategy", category = Core.CATEGORY_NAME, printObject = true)
public class DefaultRolloverStrategy extends AbstractRolloverStrategy {private static final int MIN_WINDOW_SIZE = 1;private static final int DEFAULT_WINDOW_SIZE = 7;/*** Builds DefaultRolloverStrategy instances.*/public static class Builder implements org.apache.logging.log4j.core.util.Builder<DefaultRolloverStrategy> {@PluginBuilderAttribute("max")private String max;@PluginBuilderAttribute("min")private String min;@PluginBuilderAttribute("fileIndex")private String fileIndex;@PluginBuilderAttribute("compressionLevel")private String compressionLevelStr;@PluginElement("Actions")private Action[] customActions;@PluginBuilderAttribute(value = "stopCustomActionsOnError")private boolean stopCustomActionsOnError = true;@PluginBuilderAttribute(value = "tempCompressedFilePattern")private String tempCompressedFilePattern;@PluginConfigurationprivate Configuration config;@Overridepublic DefaultRolloverStrategy build() {int minIndex;int maxIndex;boolean useMax;if (fileIndex != null && fileIndex.equalsIgnoreCase("nomax")) {minIndex = Integer.MIN_VALUE;maxIndex = Integer.MAX_VALUE;useMax = false;} else {useMax = fileIndex == null ? true : fileIndex.equalsIgnoreCase("max");minIndex = MIN_WINDOW_SIZE;if (min != null) {minIndex = Integer.parseInt(min);if (minIndex < 1) {LOGGER.error("Minimum window size too small. Limited to " + MIN_WINDOW_SIZE);minIndex = MIN_WINDOW_SIZE;}}maxIndex = DEFAULT_WINDOW_SIZE;if (max != null) {maxIndex = Integer.parseInt(max);if (maxIndex < minIndex) {maxIndex = minIndex < DEFAULT_WINDOW_SIZE ? DEFAULT_WINDOW_SIZE : minIndex;LOGGER.error("Maximum window size must be greater than the minimum windows size. Set to " + maxIndex);}}}final int compressionLevel = Integers.parseInt(compressionLevelStr, Deflater.DEFAULT_COMPRESSION);// The config object can be null when this object is built programmatically.final StrSubstitutor nonNullStrSubstitutor = config != null ? config.getStrSubstitutor() : new StrSubstitutor();return new DefaultRolloverStrategy(minIndex, maxIndex, useMax, compressionLevel, nonNullStrSubstitutor,customActions, stopCustomActionsOnError, tempCompressedFilePattern);}...}