Druid monitoring - Introduction to JMX usage and principle

Recently focused on business , There is little time to update the blog , A while ago, it was a big promotion druid Something is wrong , By the way druid Implementation of monitoring , Don't say here druid The principle of connection pool and JMX Basic knowledge of . To configure Druid There are two main ways of monitoring ：

• Mode one : adopt DruidStatManagerFacade To get DruidDataSource Relevant monitoring data ( This method is not used JMX The way ), External data related to such exposure monitoring , The user can directly create an instance and use the method to obtain . The sample code is as follows :

public class DruidStatController {
    @GetMapping("/durid/stat")
    public Object druidStat(){
        // DruidStatManagerFacade#getDataSourceStatDataList  This method can obtain the monitoring data of all data sources , besides  DruidStatManagerFacade  There are also some other ways , You can choose to use .
        return DruidStatManagerFacade.getInstance().getDataSourceStatDataList();
    }
}	

• Mode two : adopt http Request internal use JMX To obtain monitoring data , In essence, it's also through DruidStatManagerFa- cade To get DruidDataSource Relevant monitoring data . The configuration is as follows ：

        The first point ：java The project startup parameters are as follows , Open port for web End view ：

-Djava.net.preferIPv4Stack=true 
-Dcom.sun.management.jmxremote 
-Djava.rmi.server.hostname=10.8.3.221
-Dcom.sun.management.jmxremote.port=9004  
-Dcom.sun.management.jmxremote.authenticate=false

        Second point ：web In Engineering web.xml The configuration is as follows :

<!-- Druid, Monitoring the database , as well as WEB Access connection information  -->
<!--  Reference resources : https://github.com/alibaba/druid/wiki/%E9%85%8D%E7%BD%AE_%E9%85%8D%E7%BD%AEWebStatFilter -->
<filter>
	<filter-name>DruidWebStatFilter</filter-name>
	<filter-class>com.alibaba.druid.support.http.WebStatFilter</filter-class>
	<init-param>
		<param-name>exclusions</param-name>
		<param-value>*.js,*.gif,*.jpg,*.png,*.css,*.ico,*.jsp,/druid/*,/download/*</param-value>
	</init-param>
	<init-param>
		<param-name>sessionStatMaxCount</param-name>
		<param-value>2000</param-value>
	</init-param>
	<init-param>
        <param-name>sessionStatEnable</param-name>
        <param-value>true</param-value>
    </init-param>
	<init-param>
        <param-name>principalSessionName</param-name>
        <param-value>session_user_key</param-value>
    </init-param>
    <init-param>
	    <param-name>profileEnable</param-name>
	    <param-value>true</param-value>
	</init-param>
</filter>
<filter-mapping>
	<filter-name>DruidWebStatFilter</filter-name>
	<url-pattern>/*</url-pattern>
</filter-mapping>
<!--  To configure  Druid  Monitoring information display page  -->
<servlet>
	<servlet-name>DruidStatView</servlet-name>
	<servlet-class>com.alibaba.druid.support.http.StatViewServlet</servlet-class>
	<init-param>
		<!--  Allow to clear Statistics  -->
		<param-name>resetEnable</param-name>
		<param-value>true</param-value>
	</init-param>
	<init-param>
		<!--  user name  -->
		<param-name>loginUsername</param-name>
		<param-value>druid</param-value>
	</init-param>
	<init-param>
		<!--  password  -->
		<param-name>loginPassword</param-name>
		<param-value>druid</param-value>
	</init-param>
	<!--  The remote access JavaSE Project use jmx Connect  -->
    <init-param>
        <param-name>jmxUrl</param-name>
        <param-value>service:jmx:rmi:///jndi/rmi://10.8.3.221:9004/jmxrmi</param-value>
    </init-param>
</servlet>
<servlet-mapping>
	<servlet-name>DruidStatView</servlet-name>
	<url-pattern>/druid/*</url-pattern>
</servlet-mapping>

</web-app>

The main logic of this way is StatViewServlet in , If configured jmxUrl Properties will go remote JMX, The process is as follows ：

Core source code reference :

/**
     * StatViewServlet Class . The program first determines whether it exists jmx Connection address , If it doesn't exist , Then call the local duird service ;  If there is , Then call remote jmx service . It's going on jmx signal communication , First of all, let's judge jmx Whether the connection has been established successfully , If it has been established successfully ,
          Then communicate directly , If it has not been successfully established before , Will try to rebuild .
     * @param url  Service address to connect 
     * @return  Returned after calling the service json character string 
     */
    protected String process(String url) {
        String resp = null;
        if (jmxUrl == null) {
            resp = statService.service(url);
        } else {
            if (conn == null) {//  Connection creation failed during initialization 
                try {//  Try to reconnect 
                    initJmxConn();
                } catch (IOException e) {
                    LOG.error("init jmx connection error", e);
                    resp = DruidStatService.returnJSONResult(DruidStatService.RESULT_CODE_ERROR,
                                                             "init jmx connection error" + e.getMessage());
                }
                if (conn != null) {//  Successful connection 
                    try {
                        resp = getJmxResult(conn, url);
                    } catch (Exception e) {
                        LOG.error("get jmx data error", e);
                        resp = DruidStatService.returnJSONResult(DruidStatService.RESULT_CODE_ERROR, "get data error:"+ e.getMessage());
                    }
                }
            } else {//  Successful connection 
                try {
                    resp = getJmxResult(conn, url);
                } catch (Exception e) {
                    LOG.error("get jmx data error", e);
                    resp = DruidStatService.returnJSONResult(DruidStatService.RESULT_CODE_ERROR,
                                                             "get data error" + e.getMessage());
                }
            }
        }
        return resp;
    }