1. [Mandatory] Do not use API in log system (Log4j, Logback) directly. API in log framework SLF4J is recommended to use instead, which uses Facade pattern and is conducive to keep log processing consistent.

import org.slf4j.Logger; 
import org.slf4j.LoggerFactory;
private static final Logger logger = LoggerFactory.getLogger(Abc.class);

2. [Mandatory] Log files need to be kept for at least 15 days because some kinds of exceptions happen weekly.

3. [Mandatory] Naming conventions of extended logs of an Application (such as RBI, temporary monitoring, access log, etc.):
appName_logType_logName.log
logType: Recommended classifications are stats, desc, monitor, visit, etc.
logName: Log description.
Benefits of this scheme: The file name shows what application the log belongs to, type of the log and what purpose is the log used for. It is also conducive for classification and search.

Positive example: Name of the log file for monitoring the timezone conversion exception in mppserver application: mppserver_monitor_timeZoneConvert.log

Note: It is recommended to classify logs. Error logs and business logs should be stored separately as far as possible. It is not only easy for developers to view, but also convenient for system monitoring.

4. [Mandatory] Logs at TRACE / DEBUG / INFO levels must use either conditional outputs or placeholders.

Note: logger.debug ("Processing trade with id: " + id + " symbol: " + symbol); If the log level is warn, the above log will not be printed. However, it will perform string concatenation operator. toString() method of symbol will be called, which is a waste of system resources.

Positive example:

if (logger.isDebugEnabled()) { 
    logger.debug("Processing trade with id: " + id + " symbol: " + symbol); 
}

Positive example:

logger.debug("Processing trade with id: {} and symbol : {} ", id, symbol);

5. [Mandatory] Ensure that additivity attribute of a Log4j logger is set to false, in order to avoid redundancy and save disk space.

Positive example:
<logger name="com.taobao.ecrm.member.config" additivity="false" \>

6. [Mandatory] The exception information should contain two types of information: the context information and the exception stack. If you do not want to handle the exception, re-throw it.

Positive example:

logger.error(various parameters or objects toString + "_" + e.getMessage(), e);

7. [Recommended] Carefully record logs. Use Info level selectively and do not use Debug level in production environment. If Warn is used to record business behavior, please pay attention to the size of logs. Make sure the server disk is not over-filled, and remember to delete these logs in time.

Note: Outputting a large number of invalid logs will have a certain impact on system performance, and is not conducive to rapid positioning problems. Please think about the log: do you really have these logs? What can you do to see this log? Is it easy to troubleshoot problems?

8. [Recommended] Level Warn should be used to record invalid parameters, which is used to track data when problem occurs. Level Error only records the system logic error, abnormal and other important error messages.