Log4j and centralizing log collection - log4j

Question

I have an existing distributed application using log4j to write logs to the local server. I want to preserve the existing functionality and also have some of those logs sent to a central repository. I've seen examples of using log4j with SocketAppender to send a log to a remote server, but haven't seen an example of multiple server sending to the same remote server writing each server's logs in a separate file. Is there an example of this?
As an alternative, I'm curious about using the JDBCAppender using a database as the centralized log repository but have the same question regarding how do differentiate where the messages came from when viewing query results. Is there a log4j properties setting that identifies the sender that can be interpreted on the listener server?

Answer 1

For your first question - it will depend on the remote server to whom your client program is sending logs. If you have developed some program for receiving logs on remote server then, there are 2 approaches to create separate log file for each client logs -
Server program should listen on a particular port and after receiving some logs, it should check client IP and then create log file for each client IP.
Make server program to listen on different port for each client and once client is connected to its specific port, receive the data and dump in a log file. This approach seems easy but not recommended.
If your server is based on linux, I would recommend you to use rsyslog for centralizing log collection. In rsyslog, you can configure each client separately and dump the logs in separate log file.
For second question - you can use Nested diagnostic Context (NDC) feature of log4j for writing hostname in database. See this example. This example is using USER_ID as extra column for writing in database. Similarly, you can use this extra column for writing hostname. In the starting of your client program before writing any log statement, you have to put value in NDC using below code -
NDC.push(InetAddress.getLocalHost().getHostName());

Answer 2

you have to make some changes in the Configuration File. Considering multiple applications want to write their log files to the centralised remote location, If yes then the below mentioned changes would help:
You need to make the change in each individual application's Log4j config file.
<?xml version="1.0" encoding="UTF-8"?>
<Configuration monitorInterval="60">
<Properties>
<Property name="server-log-path">REMOTE_SERVER_PATH</Property>
</Properties>
<Appenders>
<File name="Login-App-File-Appender" fileName="${server-log-path}/file_name.log" >
<PatternLayout>
<pattern>
[%-5level] %d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %c{1} - %msg%n
</pattern>
</PatternLayout>
</File>
<File name="CheckOut-App-File-Appender" fileName="${server-log-path}/file_name.log" >
<PatternLayout>
<pattern>
[%-5level] %d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %c{1} - %msg%n
</pattern>
</PatternLayout>
</File>
</Appenders>
<Loggers>
<Logger name="com.microService.LoginService" level="info" additivity="false">
<AppenderRef ref="Login-App-File-Appender"/>
</Logger>
<Logger name="com.microService.CheckOutService" level="info" additivity="false">
<AppenderRef ref="CheckOut-App-File-Appender"/>
</Logger>
<Root>
<AppenderRef ref="Login-App-File-Appender"/>
</Root>
</Loggers>
</Configuration>