In order to efficiently use connection pooling via BoneCP while programming a Netty server- where is the correct place for the connection pool and where to get a new connection for that pool?
At a glance- I'm thinking that BoneCP should be some sort of global/singleton initialized just once in the main server, and then each handler (i.e. the class passed as "handler" to the pipeline) references that singleton to grab a new connection... but I don't see any examples of that on the net and, being new to Java, I'm a little concerned to jump right in with that approach. Would be great to hear an experienced voice!
Yes, a channel handler can very well use the BoneCP connection pool, but you should definitively insert an ExecutionHandler in front of the BoneCP handler. You do not want to issue blocking db calls in a netty IO worker thread.
There's also this defined in bonecp:
public ListenableFuture getAsyncConnection(){
return this.asyncExecutor.submit(new Callable<Connection>() {
public Connection call() throws Exception {
return getConnection();
}});
}
Related
I'm new to the Play! framework and I was looking at ways to connect to a DB.
In the docs there is 2 ways to get a JDBC connection, one using the DB.getDatasource() and one using the DB.getConnection() method: http://www.playframework.com/documentation/2.3.x/JavaDatabase
What is the difference between each? Pros and Cons?
getConnection() in Play Java eventually calls the getConnection function from a DBApi implementation in the Play Scala library that looks like this:
def getConnection(name: String, autocommit: Boolean = true): Connection = {
val connection = getDataSource(name).getConnection
connection.setAutoCommit(autocommit)
connection
}
This is just calling getDataSource and then retrieving a connection from it.
getDataSource() returns a javax.sql.DataSource, which as you can see the the Java API docs doesn't give you all that much to do but get a connection from it. Unless you need slightly more fine grained control, getConnection() should suffice.
I'm using org.apache.commons.dbcp.BasicDataSource as my datasource implementation, my code geting connection and closing the connection like this:
Connection conn = dataSource.getConnection();
when I finished the connection work I will close it
conn.close();
My question is: the conn.close() is really close, so when the connection be closed like conn.close(), how is datasource doing. I heard that the datasource connection close is not really close, just is release, but I can't find the release API from datasource class. I want to know how does datasource manage the creation, close and release of database connection.
By the way a little question: how does datasource refresh the connection, I mean if the connections of the datasource haven't been used for one year, how does datasource keep the connections available?
DataSource (javax.sql.DataSource) represents an abstract concept of something you can get database connections from.
So, DataSource itself doesn't define any details of how connections are managed, and different implementations of DataSource may manage connections in different ways:
A naive implementation (such as Spring's DriverManagerDataSource) may create a new connection each time you request it, and in this case close() actually closes connections.
An implementation backed by a connection pool (such as Apache DBCP or c3p0) returns existing connections from the pool. Connection object returned by such an implementation is a proxy, and its close() method is overriden to return connection to the pool instead of closing it.
If you want to know how exactly your connection pool manages connections, check documentation of your connection pool implementation.
The close() call on a connection from a datasource doesn't necessarily close the database connection. It would merely return the connection to the pool for reuse. The way this is done is, the actual connection to the database is decorated with a PooledConnection sort of class and the close() method on this PooledConnection is overridden to just mark the connection as available.
I'm looking for some advice on the proper way to set up mongoDB for my web application that runs with java.
From the mongoDB tutorial, i understand that I should have only one instance of the Mongo class.
The Mongo class is designed to be thread safe and shared among threads. Typically you create only 1 instance for a given DB cluster and use it across your app.
So I've got a singleton provider for this (I'm using guice for injection)
#Singleton
public class MongoProvider implements Provider<Mongo> {
private Mongo mongo;
public Mongo get() {
if (mongo == null)
mongo = new Mongo("localhost", 27017);
return mongo;
}
}
And whenever I have to work with mongo in my webapp i inject the provider and get the same instance of mongo.
public class MyService {
private Provider<Mongo> mongoProvider;
#Inject
private MyService(Provider<Mongo> mongoProvider) {
this.mongoProvider = mongoProvider;
}
public void execute() {
DB db = mongoProvider.get().getDB("mydatabase");
DBCollection coll = db.getCollection("mycollection");
// Do stuff in collection
...
}
}
What I find weird is that everytime i access my database, i get logs like this from mongo :
[initandlisten] connection accepted from 192.168.1.33:54297 #15
[initandlisten] connection accepted from 192.168.1.33:54299 #16
So far, I haven't had any problems but I'm wondering if it's good practice and if I won't run into any problems when the number of connections accepted gets too high.
Should I also have only one instance of the DB object for my entire app ?
Do I have to configure MongoDB differently to automatically close the connections after some time ? Or do I have to close connections manually ? I've read something about using the close() method on Mongo but I'm not sure when or if to call it.
Thank you for you advice.
This is good practice. Each instance of Mongo manages a connection pool, so you will see multiple connections in the mongod logs, one for each connection in the pool. The default pool size is 10, but that can be configures using the connectionsPerHost field in MongoOptions.
Mongo instances also maintain a cache of DB instances, so you don't have to worry about maintaining those as singletons yourself.
You do not have to configure Mongo to automatically close connections. You can call Mongo#close at the appropriate time to close all the sockets in the connection pool.
Founded something like this om MondoDB site:
"The Java MongoDB driver is thread safe. If you are using in a web serving environment, for example, you should create a single MongoClient instance, and you can use it in every request. The MongoClient object maintains an internal pool of connections to the database (default pool size of 10). For every request to the DB (find, insert, etc) the Java thread will obtain a connection from the pool, execute the operation, and release the connection. This means the connection (socket) used may be different each time."
And from FAQ from MongoSite which I think completely anwsers on you question.
http://docs.mongodb.org/manual/faq/developers/#why-does-mongodb-log-so-many-connection-accepted-events
Currently I'm using a separate DBConnectionManager class to handle my connection pooling, but I also realized that this was the wrong way to go as the servlet was not calling the same pool each time a doGet() is performed.
Can someone explain to me why the above is happening?
Is JNDI the way to go for java servlets with tomcat for proper connection pooling?
I have links to 2 articles, is this the correct way to implement connection pooling with servlets?
http://www.javaranch.com/journal/200601/JDBCConnectionPooling.html
http://onjava.com/onjava/2006/04/19/database-connection-pooling-with-tomcat.html
Is it possible to save the db manager object in the context like so:
mtdb = (MTDbManager) context.getAttribute("MTDBMANAGER");
if (mtdb == null) {
System.out
.println("MTDbManager is null, reinitialize MTDbManager");
initMTDB(config);
context.setAttribute("MTDBMANAGER", mtdb);
}
And then I call mtdb.getInstance().getConnection() and it will always reference this object.
Thanks.
Generally, the best advice is to leave the connection pooling to the application server. Just look up the data source using JNDI, and let the application server handle the rest. That makes your application portable (different application servers have different pooling mechanisms and settings) and most likely to be most efficient.
Have a look at, and use, C3P0 instead of rolling your own solution: http://sourceforge.net/projects/c3p0/
I want to use pooled connections with Java (because it is costly to create one connection per thread) so I'm using the MysqlConnectionPoolDataSource() object. I'm persisting my data source across threads. So, I'm only using one datasource throughout the application like this:
startRegistry(); // creates an RMI registry for MySQL
MysqlConnectionPoolDataSource dataSource = new MysqlConnectionPoolDataSource();
dataSource.setUser("username");
dataSource.setPassword("password");
dataSource.setServerName("serverIP");
dataSource.setPort(3306);
dataSource.setDatabaseName("dbname");
InitialContext context = createContext(); // Creates a context
context.rebind("MySQLDS", dataSource);
Now that I have my datasource created, I'm doing the following in each separate thread:
PooledConnection connect = dataSource.getPooledConnection();
Connection sqlConnection = connect.getConnection();
Statement state = sqlConnection.createStatement();
ResultSet result = state.executeQuery("select * from someTable");
// Continue processing results
I guess what I'm confused on is the call to dataSource.getPooledConnection();
Is this really fetching a pooled connection? And is this thread safe?
I noticed that PooledConnection has methods like notify() and wait()... meaning that I don't think it is doing what I think it is doing...
Also, when and how should I release the connection?
I'm wondering if it would be more beneficial to roll my own because then I'd be more familiar with everything, but I don't really want to reinvent the wheel in this case :).
Thanks SO
This is not the right way. The datasource needs to be managed by whatever container you're running the application in. The MysqlConnectionPoolDataSource is not a connection pool. It is just a concrete implementation of the javax.sql.DataSource interface. You normally define it in the JNDI context and obtain it from there. Also MySQL itself states it all explicitly in their documentation.
Now, how to use it depends on the purpose of the application. If it is a web application, then you need to refer the JNDI resources documentation of the servletcontainer/appserver in question. If it is for example Tomcat, then you can find it here. If you're running a client application --for which I would highly question the value of a connection pool--, then you need to look for a connection pooling framework which can make use of the MySQL-provided connection pooled datasource, such as C3P0.
The other problem with the code which you posted is that the PooledConnection#getConnection() will return the underlying connection which is thus not a pooled connection. Calling close on it won't return the connection to the pool, but just really close it. The pool has to create a new connection everytime.
Then the threadsafety story, that depends on the real connection pooling framework in question. C3P0 has proven its robustness in years, you don't worry about it as long as you write JDBC code according the standard idiom, i.e. use only the JDBC interfaces and acquire and close all resources (Connection, Statement and ResultSet) in shortest possible scope.