I have to implement software that listens for UDP packets and persists their contents to a database.
It would be handy if this could run in JBoss, as this is the infrastructure we are using now.
I have seen that Netty is ideally suited to program the listener part.
Is there a way to use Netty "embedded" in JBoss? I have searched up and down the Net and the examples I have found are all for standalone listener programs.
Of course, but you have to clarify what you mean by ""embedded" in JBoss". If you are writing a standard EJB application, just put Netty bootstrap code in #PostConstruct of singleton session bean and destroy it in #PreDestroy.
If it's a web application, use any servlet's init() method (servlet must be created eagerly on startup).
Note that EJB spec does not allow creating custom threads and listening on arbitrary ports - Netty violates both of these requirements. But JBoss won't enforce this.
Sounds like JCA might be the appropriate path.
Related
We have an enterprise solution deployed on Wildfly 8.0.0 server, we intend to support CoAP and MQTT also as communication protocol. We explored extensively but we couldn't find even any oblique reference to our problem case. Is it possible to add CoAP and MQTT support without destabilizing Wildfly setup ??
I think theoretically it is possible to use a https://www.eclipse.org/californium/ within an EE server for CoAP.
The main issue here is that Californium listens to an UDP port (and sends datagrams too).
So if you want to stay within a EE specification, you'll have to implement a JCA adapter for that.
If you want things to just work, you can run/manage it from a JMX bean.
WildFly being a Web Server doesn't necessarily need to support CoAP or MQTT because those are not standard HTTP based Communication protocols but protocols designed to enable M2M (Machine to Machine) Communication.
As of WildFly 8.0.0.Final it only allows HTTP (Servlet, JAX-RS, JAX-WS), Web Sockets, HTTP Upgraded Remoting (EJB Invocation, Remote JNDI).
By default, applications in wildfly are deployed to localhost:8080/app. How to deploy application on dedicated port, i.e. open it on localhost:8282 without application name ending?
I need to change the port for certain application, not the default port.
I have not tried this, but AFAICT it should be possible to:
run a single Wildfly instance listening on multiple HTTP ports. This is, in theory at least, possible (ref: https://developer.jboss.org/thread/233414?start=0&tstart=0)
Configure undertow subsystem as a reverse proxy, and proxy your app to the other port/location (ref: http://www.mastertheboss.com/jboss-server/wildfly-8/configuring-a-reverse-proxy-with-undertow). That said, I have never used undertow for a reverse proxy and as such cannot speak for whether this really works.
Once you have done this, you have effectively just turned your Wildfly instance into an overly complex application server and reverse proxy in one. Ultimately however, the app in question would still be running on both ports, but you redirect the traffic using the proxy the way you would like.
The same proxy configuration in an Apache (ref: https://httpd.apache.org/docs/current/mod/mod_proxy.html#forwardreverse or https://www.leaseweb.com/labs/2014/12/tutorial-apache-2-4-transparent-reverse-proxy/) or NGINX (ref: https://www.nginx.com/resources/admin-guide/reverse-proxy/) would be IMHO less complex and better tested in countless production scenarios.
All
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.
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.