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I am making REST client calls from an EJB container (IBM Websphere v6.1) and cannot find any way to get a HTTP connection factory from WAS.
Is this possible in WAS 6.1?
Would expect be able to access this with JNDI so connection pool configuration, socket timeout, connection timeout, connections per URL etc could be centrally managed.
If not the alternative is to use a Client API such as HttpClient 4.3. But this has its own kettle of fish:
They recommend 'BasicHttpClientConnectionManager': "This connection manager implementation should be used inside an EJB container". However this implies one connection per thread which in an application with many threads will exhaust the resources of the O/S.
The other alternative 'PoolingHttpClientConnectionManager' seems to be a much better fit with much of the required controls, but in the the comments on the the Basic manager it says explicitly that the Pooling manager shouldn't be used in a EJB container managed context. Scanning the code for this it looks like the Pooling manager uses Future from the concurrent library but doesn't appear to directly use Threads.
Any suggestions about the best way forward would be appreciated - some options seem to be:
Test with PoolingHttpClientConnectionManager - with risk of subtle problems
Play safe with 'BasicHttpClientConnectionManager' but set short response and socket timeouts to constrain the number of concurrent sockets at the cost of lots of factory overhead. Yuk.
Some other way of getting access to the pool of HTTP connections in WAS 6.1.
Something else
Any suggestions for this rather ikky problem would be ideal.
Please don't suggest upgrading WAS - although future versions ie the WAS commerce version do seem to have a JCA HTTP Adaptor and 8.5 has a built in REST client.
Please don't publish responses relating to MQ/JMS, JDBC connection pooling or setting up resource adaptors for EIS other than HTTP.
Related
in Java, application servers like JBoss EAP have the option to periodically verify the connections in a database pool (https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/6.4/html/administration_and_configuration_guide/sect-database_connection_validation). This has been very useful for removing stale connections.
I'm now looking at a ADO.NET application, and I was wondering if there was any similar functionality that could be used with a Microsoft SQL Server?
I ended up find this post by redgate that describes some of the validation that goes on when connections are taken from the pool:
If the connection has died because a router has decided that it no
longer wants to forward your packets and no other routers like you
either then there is no way to know this unless you try to send some
data and don’t get a response.
If you create a connection and a connection pool is created and
connections are put into the pool and not used, the longer they are in
there, the bigger the chance of something bad happening to it.
When you go to use a connection there is nothing to warn you that a
router has stopped forwarding your packets until you go to use it; so
until you use it, you do not know that there is a problem.
This was an issue with connection pooling that was fixed in the first
.Net 4 reliability update (see issue 14 which vaguely describes this)
with a feature called “Connection Pool Resiliency”. The update meant
that when a connection is about to be taken from the pool, it is
checked for TCP validity and only returned if it is in a good state.
I've read that the connection pool of the C++ driver doesn't work with authenticated connections (article from end of 2013).
Is this (still) true?
Looking the documentation regarding the new C++ driver (named "legacy"), it seems that the relevant classes has been removed:
The ConnectionPool and ScopedDbConnection classes have been removed.
So the situation is even worse: not only the driver doesn't provide any mechanism for implement connections pools with authentication... it doesn't provide any pool connection mechanism at all :(
The rationale is detailed in this issue at MongoDB JIRA:
At this time, we have no plans to add pooling back into the legacy driver for the upcoming 1.0 release. It should be very straightforward to implement a simple pool for your application, and you will have one that does exactly what you want
Given two web apps running on the same Tomcat 6. If you do an http-call from one app to the other, will Tomcat "short circuit" this call, or will it go all the way out on the interwebz before calling home?
#thomasz answer shows the need for more detail. We're using Springs RestTemplate to do the communication. Its plugable architecture lets you provide your own ClientHttpRequestFactory.
Would it be possible to implement a ClientHttpRequest that, if the request was to localhost, it could persuade tomcat to handle it internally?
No, the request will go through all the layers, including loopback interface. Tomcat is not treating requests to the same web container differently. After all, how? You are accessing some URL via URLConnection or HttpClient or raw socket or... - Tomcat would have to somehow intercept (instrument) your application's code and dynamically replace HTTP call with some internal invocation. Possible, but very complicated.
To make matters worse, you can easily cause deadlock or starvation under high load. Imagine your Tomcat worker thread pool has 10 threads and at the same time you access the same servlet from 10 concurrent users. Every servlet now tries to connect to the same web container, but the worker thread pool is exhausted. So all these servlets are blocking, waiting for idle worker thread. But this will never happen, because they are occupying all of them!
I need to implement a TCP server with a web interface included for management.
Basically, the tcp server will be listening to new connections and keeping current ones active while the web interface allow me to see information regarding these connections and to interact with them (e.g. send messages and seeing received ones)...
My concerns resides in the "TCP Server" integration with the web application.
For received messages I could simple use a shared DB, but I need to send messages to the peers connected into the TCP server.
My best bet is currently on JCA. Some research pointed me to a nice sample: http://code.google.com/p/jca-sockets.
The sample uses an Message Driven Bean to deal with messages received over port 9000, acting as an echo server.
I am new in the Java EE 6 world. I trying to figure out why things were done in one way or another in the sample (e.g. why MDB?).
JCA has a fairly complicated spec. So I am trying at first to adapt the sample above to keep the connections active to exchange data. My next step will be adapt it to accept a string over a servlet to forward it to a given peer.
Can someone help me out on this?
Well, first of all, using Java EE with TCP is not the best approach you may use. If you just need a simple TCP service with Web UI you'd better consider using Java SE with some web container attached (undertow works well).
In other hand, if you need your application to integrate into existing Java EE infrastructure your company has, JCA would be the best approach. While it's not designed for such kind of things, JCA is the only EE subsystem liberal enough for that kind of thread management you would need for TCP networking to work.
JCA-Socket you're referring above is not the best example of a JCA app. It uses plain Java's blocking sockets by blocking WorkManager thread, this is not very effective. Things got much better now and we have Java NIO and Netty for highly effective raw networking to work upon. I have a JCA connector for TCP interactions which may provide you a skeleton to build your own. Feel free to extend and contribute.
P.S. About MDB: message-driven bean is the only "legal" JCA approach of asynchronous incoming messages handling. Since TCP is asynchronous, you'll definitely need one in your application for all the things to start working. Outcoming data transfers happen through various ConnectionFactory interfaces you'll inject into your bean. The link above will provide you with a reference ConnectionFactory implementation as well as a simple tester app utilizing both ConnectionFactory and MDB messaging approaches.
I have J2EE Application where I am using JPA/Toplink now I want to implement external or internal connection pool ... please help me to figure out how to implement connection pooling with JPA/TopLink ...
Well you shouldn't implement a connection pool yourself.
If your app is running inside an app server (JBoss, Glassfish..) your JPA code will use the connection pools that are configured by the app server. If you are running standalone you can use any of the number of existing open source connection pool implementations such as DBCP.
I agree with Gregory, you don't want to write a connection pool yourself. Have a look at e.g. Proxool or Commons DBCP which are both well-tested opensource connection pools.
Proxool, in my opinion, has the advantage of being trivial to add to an existing project.