扩展log4j appender发送tcp日志

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之前使用logstash采集log4j日志，使用logstash-tcp-input插件，log4j使用SocketAppender；

发现log4j的socket竟然不支持layout，所以logstash收到的消息就只有%m里的东西，，，什么时间啊，线程啊这些统统收不到；

所以，我要重写appender来发送socket消息

log4j自带的socketAppender是org.apache.log4j.net.SocketAppender，

继承关系如下

java.lang.Object

    org.apache.log4j.AppenderSkeleon

                org.apache.log4j.net.SocketAppender

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因此自定义appender继承自AppenderSkeleon（原本打算继承SocketAppender，研究后发现，这样没办法实现我的需求） 

import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.Layout;
import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.spi.LoggingEvent;

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;


/**
 * 用于logstash的socket模块，，解决各种问题
 *
 * @author 墨盒
 */
public class LogstashSocketAppender extends AppenderSkeleton {

    private Layout layout;
    private String host;
    private OutputStreamWriter out;
    private int port = 4560;
    private String ip;
    private boolean syn = false;//同步或异步
    private boolean requireIp = true;//是否需要输出ip

    public LogstashSocketAppender() {
    }

    public void setSyn(boolean syn) {
        this.syn = syn;
    }

    public void setRequireIp(boolean requireIp) {
        this.requireIp = requireIp;
    }

    private void getIp() {
        if (requireIp) {
            try {
                ip = InetAddress.getLocalHost().getHostAddress() + "-";
            } catch (UnknownHostException e) {
                e.printStackTrace();
            }
        } else {
            ip = "";
        }
    }

    public void setHost(String host) {
        this.host = host;
    }

    public void setPort(int port) {
        this.port = port;
    }

    private void connect() {
        try {
            if (syn) {
                new Thread(() -> {
                    try {
                        createOut();
                    } catch (IOException e) {
                        e.printStackTrace();
                        LogLog.warn("can't connect the " + this.host);
                    }
                }).start();
            } else {
                createOut();
            }
        } catch (Exception e) {
            LogLog.error("can't connect the " + this.host);
        }

    }

    private void createOut() throws IOException {
        out = new OutputStreamWriter(new Socket(this.host, this.port).getOutputStream());
    }

    @Override
    public void activateOptions() {
        connect();
        getIp();
    }

    @Override
    protected void append(LoggingEvent loggingEvent) {
        if (this.out != null && this.layout != null) {
            String message = this.layout.format(loggingEvent);
            try {
                if (syn && out != null) {//完成连接前的日志都将丢失
                    new Thread(() -> {
                        try {
                            out.write(System.currentTimeMillis() + "-" + ip + message);
                            out.flush();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }).start();
                } else {
                    this.out.write(System.currentTimeMillis() + "-" + ip + message);
                    this.out.flush();
                }

            } catch (IOException e) {
                if (e instanceof InterruptedIOException) {
                    Thread.currentThread().interrupt();
                }
                this.out = null;
                LogLog.error("send socket message fail");
            }
        }
    }

    @Override
    public void close() {
        if (this.out != null) {
            try {
                this.out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void setLayout(Layout layout) {
        this.layout = layout;
    }

    @Override
    public boolean requiresLayout() {
        return true;
    }


}

改appender支持异步发送消息，注意，如果logger初始化的时候，日志接收端未启动，不影响程序运行，在socket超时时间内启动接收端即可收到日志，但是在此之前的日志将会丢失

log4j配置使用方法如下

log4j.appender.logstash=cn.inkroom.web.frame.log.LogstashSocketAppender
# socket接收端ip
log4j.appender.logstash.host=127.0.0.1
# socket接收端端口，默认4560
log4j.appender.logstash.port=4566
# 是否采用异步输出，默认false
log4j.appender.logstash.syn=true
# 是否需要在日志消息前加入ip，默认为false
log4j.appender.logstash.requireIp=true
# 消息模板
log4j.appender.logstash.layout=org.apache.log4j.PatternLayout
log4j.appender.logstash.layout.ConversionPattern=(四期) %d %p [%c] - <%m>%n

注：暂不支持socket断线重连  

再注：由于我写这个是为了做日志采集，因此每条消息前会自动带入一个时间戳，em......想要去掉的话，就去直接改源码吧。。。。懒得再动了