How to Debug / Log Tomcat JDBC Connection Pool's connections?

Question

I am using Tomcat JDBC connection pool along with Spring boot, JDBC template and SQL Server. I need to know what is going inside connection pool while application is waiting for database connection. Such as....

• No of active connections
• No of idle connections
• No of blocked connections, additional info why this connection is blocked
• No of available connections
• and ...

Is there any way to get these info by debugging or using logging frameworks like log4j?

Any idea will be appreciated.

Answer 1

After a lot of research, I am able to find 3 ways to log & monitor database connection pool.

https://tomcat.apache.org/tomcat-8.0-doc/jdbc-pool.html

1. Monitoring using Spring Boot properties.

2. Monitoring using JMX ( Java Management Extensions ) (as @nitin suggested)

3. Monitoring using Spring Aspects.

1st Way: Monitoring using Spring Boot properties.

I found below Spring boot properties which will be much useful to log & monitor database connection pool.

These properties (and some more too) were not documented. Please refer below github issue for more details. https://github.com/spring-projects/spring-boot/issues/1829

#Maximum no.of active connections
spring.datasource.max-active=10

#Log the stack trace of abandoned connection
spring.datasource.log-abandoned=true

#Remove abandoned connection,So, new connection will be created and made available to threads which are waiting for DB connection
spring.datasource.remove-abandoned=true

#If any connection is not used for 10 seconds, consider that connection as "abandoned"
spring.datasource.remove-abandoned-timeout=10 

#Number of ms to wait before throwing an exception if no connection is available.
spring.datasource.max-wait=1000

This list contains more properties which are related to datasource only.(taken from the link above)

spring.datasource.abandon-when-percentage-full
spring.datasource.access-to-underlying-connection-allowed
spring.datasource.alternate-username-allowed
spring.datasource.auto-commit
spring.datasource.catalog
spring.datasource.commit-on-return
spring.datasource.connection-customizer
spring.datasource.connection-customizer-class-name
spring.datasource.connection-init-sql
spring.datasource.connection-init-sqls
spring.datasource.connection-properties
spring.datasource.connection-test-query
spring.datasource.connection-timeout
spring.datasource.data-source
spring.datasource.data-source-class-name
spring.datasource.data-source-j-n-d-i
spring.datasource.data-source-properties
spring.datasource.db-properties
spring.datasource.default-auto-commit
spring.datasource.default-catalog
spring.datasource.default-read-only
spring.datasource.default-transaction-isolation
spring.datasource.driver-class-loader
spring.datasource.fair-queue
spring.datasource.idle-timeout
spring.datasource.ignore-exception-on-pre-load
spring.datasource.init-s-q-l
spring.datasource.initialization-fail-fast
spring.datasource.isolate-internal-queries
spring.datasource.jdbc-interceptors
spring.datasource.jdbc-url
spring.datasource.jdbc4-connection-test
spring.datasource.leak-detection-threshold
spring.datasource.log-abandoned
spring.datasource.log-validation-errors
spring.datasource.log-writer
spring.datasource.login-timeout
spring.datasource.max-age
spring.datasource.max-lifetime
spring.datasource.max-open-prepared-statements
spring.datasource.maximum-pool-size
spring.datasource.metrics-tracker-class-name
spring.datasource.minimum-idle
spring.datasource.num-tests-per-eviction-run
spring.datasource.pool-name
spring.datasource.pool-prepared-statements
spring.datasource.pool-properties
spring.datasource.propagate-interrupt-state
spring.datasource.read-only
spring.datasource.record-metrics
spring.datasource.register-mbeans
spring.datasource.remove-abandoned
spring.datasource.remove-abandoned-timeout
spring.datasource.rollback-on-return
spring.datasource.suspect-timeout
spring.datasource.test-on-connect
spring.datasource.thread-factory
spring.datasource.transaction-isolation
spring.datasource.use-disposable-connection-facade
spring.datasource.use-equals
spring.datasource.use-lock
spring.datasource.validation-interval
spring.datasource.validation-query-timeout
spring.datasource.validator
spring.datasource.validator-class-name
spring.datasource.xa
spring.datasource.xa.data-source-class-name
spring.datasource.xa.properties

2nd Way: Monitoring using JMX ( Java Management Extensions )

Tomcat JDBC pool provides a MBean namely ConnectionPoolMBean.

https://tomcat.apache.org/tomcat-7.0-doc/api/org/apache/tomcat/jdbc/pool/jmx/ConnectionPoolMBean.html

Spring Boot registers JMX MBeans automatically.So, no need to register/export this MBean into MBean server. Just open the JConsole which is coming with JDK, To open, In Windows-> Command prompt ->jconsole, thats it. Refer below screenshot for more info.

This MBean also notifies whenever a connection is abandoned, connection failed, when a query is taking long time etc. Refer screenshot below.

3rd Way: Monitoring using Spring Aspects (only for development/QA environment).

I use this aspect to log TomcatJdbc Connection Pool.

I created a Spring Aspect which will intercept every database call.This will surely affect the performance.

So, use this aspect in development/QA environment,comment out this method when it is not required (for example : during production deployment).

@Before("execution(* com.test.app.db.dao.*.*(..))")
    public void logBeforeConnection(JoinPoint jp) throws Throwable {
        String methodName = "";
        methodName += jp.getTarget().getClass().getName();
        methodName += ":";
        methodName += jp.getSignature().getName();
        logger.info("before method call : " + methodName +  " : number of connections in use by the application (active) : "+ tomcatJdbcPoolDataSource.getNumActive());
        logger.info("before method call : " + methodName +  " : the number of established but idle connections : "+ tomcatJdbcPoolDataSource.getNumIdle());
        logger.info("before method call : " + methodName +  " : number of threads waiting for a connection : "+ tomcatJdbcPoolDataSource.getWaitCount());
    }


@After("execution(* com.test.app.db.dao.*.*(..)) ")
public void logAfterConnection(JoinPoint jp) throws Throwable {
    String methodName = "";
    methodName += jp.getTarget().getClass().getName();
    methodName += ":";
    methodName += jp.getSignature().getName();
    logger.info("after method call : " + methodName +  " : number of connections in use by the application (active) : "+ tomcatJdbcPoolDataSource.getNumActive());
    logger.info("after method call : " + methodName +  " : the number of established but idle connections : "+ tomcatJdbcPoolDataSource.getNumIdle());
    logger.info("after method call : " + methodName +  " : number of threads waiting for a connection : "+ tomcatJdbcPoolDataSource.getWaitCount());
    //tomcatJdbcPoolDataSource.checkAbandoned();
}

Now, you can easily identify the particular database call which creates connection leak in your application.

Answer 2

Thanks @Sundararaj Govindasamy for great answer. Based on it, I created a component in my Spring Boot Application to debug my Database Pool information.

import org.apache.tomcat.jdbc.pool.DataSource;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class DataSourceAspectLogger {

    protected final Logger logger = LoggerFactory.getLogger(this.getClass());

    @Autowired
    private DataSource ds;

    @Before("execution(* br.com.foo.core.repository.*.*(..))")
    public void logBeforeConnection(JoinPoint jp) throws Throwable {
        logDataSourceInfos("Before", jp);
    }

    @After("execution(* br.com.foo.core.repository.*.*(..)) ")
    public void logAfterConnection(JoinPoint jp) throws Throwable {
        logDataSourceInfos("After", jp);
    }

    public void logDataSourceInfos(final String time, final JoinPoint jp) {
        final String method = String.format("%s:%s", jp.getTarget().getClass().getName(), jp.getSignature().getName());
        logger.info(String.format("%s %s: number of connections in use by the application (active): %d.", time, method, ds.getNumActive()));
        logger.info(String.format("%s %s: the number of established but idle connections: %d.", time, method, ds.getNumIdle()));
        logger.info(String.format("%s %s: number of threads waiting for a connection: %d.", time, method, ds.getWaitCount()));
    }
}

Answer 3

This is a pure JSP page MBean debugger, easy to use in every Tomcat release without external dependencies. Call dumpMBean.jsp?name=ConnectionPool to list dbpool or leave name empty to dump all MBeans.

<%@ page contentType="text/plain; charset=UTF-8" pageEncoding="ISO-8859-1"
  session="false"
  import="java.io.*, java.util.*, java.net.*,
  javax.management.*, java.lang.management.ManagementFactory
  "
%><%!

private void dumpMBean(MBeanServer server, ObjectName objName, MBeanInfo mbi, Writer writer) throws Exception {
    writer.write(String.format("MBeanClassName=%s%n", mbi.getClassName()));
    Map<String,String> props=new HashMap<String,String>();
    int idx=0;
    for(MBeanAttributeInfo mf : mbi.getAttributes()) {
        idx++;
        try {
            Object attr = server.getAttribute(objName, mf.getName());
            if (attr!=null)
                props.put(mf.getName(), attr.toString());
        } catch(Exception ex) {
            // sun.management.RuntimeImpl: java.lang.UnsupportedOperationException(Boot class path mechanism is not supported)
            props.put("error_"+idx, ex.getClass().getName()+" "+ex.getMessage());
        }
    }
    // sort by hashmap keys
    for(String sKey : new TreeSet<String>(props.keySet()))
        writer.write(String.format("%s=%s%n", sKey, props.get(sKey)));
}

%><%
// Dump MBean management properties, all beans or named beans
// dumpMBean.jsp?name=ConnectionPool,ContainerMBean
// dumpMBean.jsp?name=

if (request.getCharacterEncoding()==null)
    request.setCharacterEncoding("UTF-8");

String val = request.getParameter("name");
String[] names = val!=null ? val.trim().split(",") : new String[0];
if (names.length==1 && names[0].isEmpty()) names=new String[0];

MBeanServer server = ManagementFactory.getPlatformMBeanServer();
for(ObjectName objName : server.queryNames(null,null)) {
    MBeanInfo mbi = server.getMBeanInfo(objName);
    boolean match = names.length<1;
    String name = mbi.getClassName();
    for(int idx=0; idx<names.length; idx++) {
        if (name.endsWith(names[idx])) {
            match=true;
            break;
        }
    }
    if (match) {
        dumpMBean(server, objName, mbi, out);
        out.println("");
    }
}
out.flush();

%>