如何在運行時更改特定用戶/線程的日志級別

Question

我正在使用slf4j與log4j 2.0或logback作為實現。 例如，我的s​​ervlet有一個級別為ERROR的記錄器，我的服務器產生了servlet的100個線程。 我將在運行時獲得一個特殊用戶列表。 當我檢測到一些連接的特殊用戶時。我想將這些特殊用戶/線程的日志級別更改為DEBUG，並使其他線程的日志級別不受影響（仍然是ERROR）。

我知道logback中的TurboFilter和log4j 2.0中的DynamicThresholdFilter，但由於我只在運行時獲取特殊用戶列表，所以我無法使用它們。

這是我的申請：

package com.example.logging;

import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpServlet;

import org.slf4j.*;

public class App extends HttpServlet {

    private final Logger Logger = LoggerFactory.getLogger(App.class);
    Map<String, String> map = new HashMap<String, String>();

    public App() {
        map.put("user1", "DEBUG");
        map.put("user2", "DEBUG");
        map.put("user3", "ERROR");
    }

    public void writeToLogFile(String userName) {

        if (map.containsKey(userName)) {
            // do something so that I can change the logger to the corresponding log level
        }

        Logger.error(userName + " error message");

        // the logger is of level ERROR, so by default, this log event will not happen
        // but I want it to happen for special users
        if (Logger.isDebugEnabled()) {
            Logger.debug(userName + " debug message");
        }
    }
}

這是我在log4j2.xml中的日志配置

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="ERROR">
<Appenders>
    <Console name="Console" target="SYSTEM_OUT">
        <PatternLayout pattern="%-5level %class{36} %M %msg%xEx%n" />
    </Console>
</Appenders>
<Loggers>
    <Logger name="com.example.logging.App" level="ERROR" additivity="false">
            <AppenderRef ref="Console" />
    </Logger>
    <Root level="DEBUG">
        <AppenderRef ref="Console" />
    </Root>
</Loggers> 
</Configuration>

如果我調用以下方法：

App myApp = new App();
// assume the below 4 methods are called concurrently
myApp.writeToLogFile("user1");
myApp.writeToLogFile("user2");
myApp.writeToLogFile("user3");
myApp.writeToLogFile("user4");

預期產量應為：

ERROR com.example.logging.App writeToLogFile - user1 error message
DEBUG com.example.logging.App writeToLogFile - user1 debug message
ERROR com.example.logging.App writeToLogFile - user2 error message
DEBUG com.example.logging.App writeToLogFile - user2 debug message
ERROR com.example.logging.App writeToLogFile - user3 error message
ERROR com.example.logging.App writeToLogFile - user4 error message

Answer 1

雖然現有的答案可能有效（沒有親自嘗試過），但經過深入搜索后，我發現了一個非常簡單明了的技巧來完成你的要求。

DynamicThresholdFilter可以與條件一起使用，以在運行時切換日志級別。 這與log4j2的ThreadContext相結合，你可以做很多漂亮的事情。

您必須根據用戶名的自定義邏輯，在服務器調用處理開始時（在HttpServlet類的doFilter方法中的某個位置）填充ThreadContext中的特定鍵。 這看起來像是這樣的：

ThreadContext.put("customLogLevel", "debug");

然后在log4j2.xml文件中，將其作為全局過濾器放在根Configuration標記的正下方：

<DynamicThresholdFilter key="customLogLevel" onMatch="ACCEPT" onMismatch="NEUTRAL">
    <KeyValuePair key="debug" value="DEBUG"/>
    <KeyValuePair key="error" value="ERROR"/>
    <KeyValuePair key="info" value="INFO"/>
</DynamicThresholdFilter>

現在，根據您在調用開始時設置的ThreadContext中的鍵customLogLevel的值，該customLogLevel中的所有日志調用都將具有與匹配的KeyValuePair行對應的日志級別。 因此在上面的示例中，線程中的所有日志調用都將具有DEBUG級別。

Answer 2

我遇到了同樣的問題，最后通過更改DynamicThresholdFilter來使用我自己的過濾器

對應用程序的更改：

package com.example.logging;

import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpServlet;

import org.slf4j.*;

public class App extends HttpServlet {

    private final Logger Logger = LoggerFactory.getLogger(App.class);
    Map<String, String> map = new HashMap<String, String>();

    public App() {
        map.put("user1", "Debug");
        map.put("user2", "Debug");
        map.put("user3", "Error");
    }

    public void writeToLogFile(String userName) {
        // if the user is in the map, we put it into ThreadConext for filtering
        if (map.containsKey(userName)) {
            MDC.put("level", map.get(userName));
        }

        Logger.error(userName + " error message");

        if (Logger.isDebugEnabled()) {
            Logger.debug(userName + " debug message");
        }

            // remember to remove it
        MDC.remove("level");
    }

}

這是基於DynamicThresholdFilter的新定義的過濾器，我們稱之為DynamicThresholdUserFilter，您可以將它與DynamicThresholdFilter的源代碼進行比較

package com.example.logging.log4j2.plugin;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Marker;
import org.apache.logging.log4j.ThreadContext;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.Logger;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.filter.AbstractFilter;
import org.apache.logging.log4j.message.Message;

/**
 * Compare against a log level that is associated with an MDC value.
 */
@Plugin(name = "DynamicThresholdUserFilter", category = "Core", elementType = "filter", printObject = true)
public final class DynamicThresholdUserFilter extends AbstractFilter {
    private Level defaultThreshold = Level.ERROR;
    private final String key;

    private DynamicThresholdUserFilter(final String key, final Level defaultLevel,
                                   final Result onMatch, final Result onMismatch) {
        super(onMatch, onMismatch);
        if (key == null) {
            throw new NullPointerException("key cannot be null");
        }
        this.key = key;
        this.defaultThreshold = defaultLevel;
    }

    public String getKey() {
        return this.key;
    }

    @Override
    public Result filter(final Logger logger, final Level level, final Marker marker, final String msg,
                         final Object... params) {
        return filter(level);
    }

    @Override
    public Result filter(final Logger logger, final Level level, final Marker marker, final Object msg,
                         final Throwable t) {
        return filter(level);
    }

    @Override
    public Result filter(final Logger logger, final Level level, final Marker marker, final Message msg,
                         final Throwable t) {
        return filter(level);
    }

    @Override
    public Result filter(final LogEvent event) {
        return filter(event.getLevel());
    }

    /* biggest change here */
    private Result filter(final Level level) {
        final String value = ThreadContext.get(key);
        if (value != null) {
            Level ctxLevel = Level.toLevel(value);
            if (ctxLevel == null) {
                // in case the level is invalid
                ctxLevel = defaultThreshold;
            }
            return level.isAtLeastAsSpecificAs(ctxLevel) ? onMatch : onMismatch;
        }
        return Result.NEUTRAL;

    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder();
        sb.append("key=").append(key);
        sb.append(", default=").append(defaultThreshold);
        return sb.toString();
    }

    /**
     * Create the DynamicThresholdFilter.
     * @param key The name of the key to compare.
     * @param pairs An array of value and Level pairs.
     * @param levelName The default Level.
     * @param match The action to perform if a match occurs.
     * @param mismatch The action to perform if no match occurs.
     * @return The DynamicThresholdFilter.
     */
    @PluginFactory
    public static DynamicThresholdUserFilter createFilter(
            @PluginAttribute("key") final String key,
            @PluginAttribute("defaultThreshold") final String levelName,
            @PluginAttribute("onMatch") final String match,
            @PluginAttribute("onMismatch") final String mismatch) {
        final Result onMatch = Result.toResult(match);
        final Result onMismatch = Result.toResult(mismatch);
        final Level level = Level.toLevel(levelName, Level.ERROR);
        return new DynamicThresholdUserFilter(key, level, onMatch, onMismatch);
    }
}

將DynamicThresholdUserFilter和包名稱添加到配置文件中

<?xml version="1.0" encoding="UTF-8"?>
<!-- add the package name of the filter-->
<Configuration status="ERROR" packages="com.example.logging.plugin">
    <!-- configuration of the new defined filter -->
    <DynamicThresholdUserFilter key="level" defaultThreshold="ERROR" onMatch="ACCEPT" onMismatch="NEUTRAL" />
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%-5level %class{36} %M %msg%xEx%n"/>
        </Console>
    </Appenders>
    <Loggers>
        <Logger name="com.example.logging.App" level="ERROR" additivity="false">
            <AppenderRef ref="Console" />
        </Logger>
        <Root level="debug">
            <AppenderRef ref="Console" />
        </Root>
    </Loggers>
</Configuration>

新定義的過濾器與DynamicThresholdFilter非常相似。 不同之處在於DynamicThresholdFilter使用配置文件中的預定義級別作為動態閾值，而此過濾器使用地圖中以編程方式定義的級別。