We Keep Coding

All the threads are waiting on some barrier condition

I have class like this.
class EmployeeTask implements Runnable {
public void run(){
PayDAO payDAO = new payDAO(session);
String newSalary= payDAO.getSalary(empid);
String newTitle= payDAO.getTitle(empid);
EmployeeDAO employeeDAO = new EmployeeDAO(session);
List<Employee> employees = employeeDAO.getEmployees();
employees.parallelStream().foreach(employee-> employeeDAO.add(newSalary, newTitle,employee));
}
}
When I run the above code for one thread, it completes DB operation in 1 second and returns.
When I run it using parallelStream(), it will submit 8 requests, all 8 threads will wait for eight seconds and then return. Which means the server is executing the requests sequentially instead of parallel.
I checked the java jetty logs
Theread-1 Insert …
Theread-2 Insert …
…
Theread-8 Insert …
After eight seconds, that is 1 second per request
Theread-1 Insert … <= update 1
Theread-2 Insert … <= update 1
…
Theread-8 Insert … <= update 1
the same thing continues.
This clearly tells, all the threads are getting blocked on one single resource, either the Datasource from my client java has only one connection so all the eight threads are getting blocked or the server is executing the requests one after the other.
I checked MaxPooledConnections — gives 20, MaxPooledConnections
PerNode - gives 5 default values.
I think the Vertica DB server is fine, maybe client is not having DatasourceConnection pooling, How do I enable Java side DatasourceConnection pooling. Any Code examples?
currently I am using mybatis ORM, with following datasource
<environments default=“XX”>
<environment id=“XX”>
<transactionManager type=“JDBC”/>
<dataSource type="POOLED">
<property name="driver" value="com.vertica.jdbc.Driver"/>
<property name="url" value="jdbc:vertica://host:port/schema”/>
<property name="username" value=“userName”/>
<property name="password" value=“password”/>
<property name="poolMaximumActiveConnections" value=“50”/>
<property name="poolMaximumIdleConnections" value=“10”/>
</dataSource>
</environment>
</environments>
What is the barrier condition all the threads are waiting on, my guess is Datasource connection. Any help is appreciated
Thanks.

Connection is invalid in connection pooling

I am using c3p0 for connection poolingin my java application. We write the all properties related to it and i am having wait_timeout value is 60. We can not increase wait_timeout value. I got error "connection is invalid". How to handle this error.

you should set max_idle_time for waiting timeout ; for example :
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">50</property>
<property name="hibernate.c3p0.timeout">15</property>
<property name="hibernate.c3p0.max_idle_time">60</property>
<property name="hibernate.c3p0.max_statements">50</property>
<property name="hibernate.c3p0.idle_test_period">10</property>
see this link : http://www.mchange.com/projects/c3p0/index.html#configuration_files
you can find same question in stack overflow fro example :
Hibernate c3p0 connection pool not timing out idle connections
c3p0 maxIdleTime is same as wait_timeout of mysql?

Jedis Get Data: JedisConnectionFailureException iterating a section of code over long period of time

So I have a code that gets value from Redis using Jedis Client. But at a time, the Redis was at maximum connection and these exceptions were getting thrown:
org.springframework.data.redis.RedisConnectionFailureException
Cannot get Jedis connection; nested exception is redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool
at org.springframework.data.redis.connection.jedis.JedisConnectionFactory.fetchJedisConnector(JedisConnectionFactory.java:140)
at org.springframework.data.redis.connection.jedis.JedisConnectionFactory.getConnection(JedisConnectionFactory.java:229)
...
org.springframework.data.redis.RedisConnectionFailureException
java.net.SocketTimeoutException: Read timed out; nested exception is redis.clients.jedis.exceptions.JedisConnectionException: java.net.SocketTimeoutException: Read timed out
at org.springframework.data.redis.connection.jedis.JedisExceptionConverter.convert(JedisExceptionConverter.java:47)
at org.springframework.data.redis.connection.jedis.JedisExceptionConverter.convert(JedisExceptionConverter.java:36)
...
org.springframework.data.redis.RedisConnectionFailureException
Cannot get Jedis connection; nested exception is redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool
at org.springframework.data.redis.connection.jedis.JedisConnectionFactory.fetchJedisConnector(JedisConnectionFactory.java:140)
at org.springframework.data.redis.connection.jedis.JedisConnectionFactory.getConnection(JedisConnectionFactory.java:229)
When I check an AppDynamics analysis of this scenario, I saw some iteration of some calls over a long period of time (1772 seconds). The calls are shown in the snips.
Can anyone explain what's happening here? And why Jedis didn't stop after the Timeout setting (500ms)? Can I prevent this from happening for long?
This is what my Bean definitions for the Jedis look like:
<bean id="jedisConnectionFactory" class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory" p:host-name="100.90.80.70" p:port="6382" p:timeout="500" p:use-pool="true" p:poolConfig-ref="jedisPoolConfig" p:database="3" />
<bean id="jedisPoolConfig" class="redis.clients.jedis.JedisPoolConfig">
<property name="maxTotal" value="1000" />
<property name="maxIdle" value="10" />
<property name="maxWaitMillis" value="500" />
<property name="testOnBorrow" value="true" />
<property name="testOnReturn" value="true" />
<property name="testWhileIdle" value="true" />
<property name="numTestsPerEvictionRun" value="10" />
</bean>

I'm not familiar with the AppDynamics output. I assume that's a cumulative view of Threads and their sleep times. So Threads get reused and so the sleep times add up. In some cases, a Thread gets a connection directly, without any waiting and in another call the Thread has to wait until the connection can be provided. The wait duration depends on when a connection becomes available, or the wait limit is hit.
Let's have a practical example:
Your screenshot shows a Thread, which waited 172ms. Assuming the sleep is only called within the Jedis/Redis invocation path, the Thread waited 172ms in total to get a connection.
Another Thread, which waited 530ms looks to me as if the first attempt to get a connection wasn't successful (which explains the first 500ms) and on a second attempt, it had to wait for 30ms. It could also be that it waited 2x for 265ms.
Sidenote:
1000+ connections could severely limit scalability. Spring Data Redis also supports other drivers which don't require pooling but work with fewer connections (see Spring Data Redis Connectors and here).

Too many connections using c3p0 and hibernate in MySql

I'm using c3p0 for my connection pooling. I've configured min connections as 100 and max size as 2000. I'm just writing a simple insert program to check how many connections are active in workbench. But, I'm getting the following error
java.sql.SQLException: Data source rejected establishment of connection, message from server: "Too many connections"
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:650)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:1808)
at com.mysql.jdbc.Connection.<init>(Connection.java:452)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:411)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
My Hibernate.cfg.xml is as follows
<!-- c3p0 Connection pool config -->
<property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property>
<property name="hibernate.c3p0.min_size">100</property>
<property name="hibernate.c3p0.max_size">2000</property>
<property name="hibernate.c3p0.timeout">300</property>
<property name="hibernate.c3p0.max_statements">50</property>
<property name="hibernate.c3p0.idle_test_period">3000</property>
<property name="hibernate.c3p0.validate">true</property>
My Java program is
public static void main(String[] args) {
// TODO Auto-generated method stub
Transaction tx = null;
SessionFactory factory = HibernateUtil.getSessionFactory();
Session session = factory.openSession();
tx = session.beginTransaction();
System.setProperty("net.sf.ehcache.skipUpdateCheck", "true");
Employee e = new Employee(2,"Richard");
session.save(e);
try {
Thread.sleep(20000);
} catch (Exception e2) {
e2.printStackTrace();
}
tx.commit();
session.close();
System.out.println("Great! Student was saved");
}
It works fine when the min size is 5 and max size is 20. Do I need to do any changes in MySQL workbench?

The whole purpose of a database connection pool (like c3p0) is to optimise the use of resources versus the database.
If you had 6000 users with 6000 connections, you would quickly exhaust the available connections and errors would result.
Instead, a connection pool allows your application to "borrow" database connections from the pool, and return them after use.
So even though you have potentially 6000 users, the moments of time when multiple users are doing operations that operate versus the database concurrently at that moment in time would be a small fraction of that.
I would suggest to try this as a more reasonable value:
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">100</property>
After setting it up like this, I would run the application and watch the number of connections versus the database. If the 100 connections are at any time exhausted, you could look at tuning it upwards.
But I suspect that 100 concurrent connections will be enough - remember that they are "borrowed" from the c3p0 connection pool.
Documentation: What is c3p0? (connection pooling)

Java. Cannot open connection

I'm using
oracle.ucp.jdbc.PoolDataSource
for getting connections. Each connection wrapped to custom class (historic solution). Generally connection is getting by entityManager. My system require hight performance processing. There is ThreadPool using for it. Thread pool can provide 15 threads at the same time, like connection pool.
Every thing works fine, but sometimes i get exception (in this moment were used only 4 connections):
2012-09-26 17:51:45.835 | ERROR | ThreadExecutor-7 | org.hibernate.ejb.AbstractEntityManagerImpl | Exception in thread "ThreadExecutor-7"
javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Cannot open connection
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1235)
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1168)
at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:1245)
at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:63)
...
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
Caused by: org.hibernate.exception.GenericJDBCException: Cannot open connection
at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:140)
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:128)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:52)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:449)
at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)
at org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:142)
at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:85)
at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1463)
at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:60)
...
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)
If i synchronize specified getConnection performance of the system going down 8-12 times.
Is any ideas for fix?

Please check you are setting appropriate values for
<property name="minPoolSize" value="5"/>
<property name="maxPoolSize" value="100"/>//Change if you want
<property name="initialPoolSize" value="5"/>
<property name="validateConnectionOnBorrow" value="true"/>
<property name="maxStatements" value="10"/>
You can check configuration here
You should change connection pooling in hibernate.
http://docs.jboss.org/hibernate/orm/3.3/reference/en/html/session-configuration.html
Hibernate's own connection pooling algorithm is, however, quite rudimentary. It is intended to help you get started and is not intended for use in a production system, or even for performance testing. You should use a third party pool for best performance and stability. Just replace the hibernate.connection.pool_size property with connection pool specific settings. This will turn off Hibernate's internal pool. For example, you might like to use c3p0.
hibernate.c3p0.min_size=5
hibernate.c3p0.max_size=20
hibernate.c3p0.timeout=1800
hibernate.c3p0.max_statements=50