I wanted to run my Grails application (version 4.0.4) in a cluster. I tried to apply Hazelcast to replicate the HTTP session across the nodes/instances but somehow I couldn’t override/replace the SessionRepository bean that Grails uses with the Hazelcast implementation.
My working configuration in Spring Boot is: I declare the Hazelcast bean and annotate the Application with #EnableHazelcastHttpSession which in turn introduces the new SessionRepository from Hazelcast.
But I couldn’t make this configuration work in Grails and override the SessionRepository. (Although the app starts, it acts very strange.)
Any ideas?
Or do you suggest an alternative approach to implement a distributed session in Grails? How did you replicate session from your past experience?
(P.S The reason I chose Hazelcast is, since it is a distributed cache which can be embedded with the application itself, I can avoid dependency on external service such as Redis, to run the app. That is part of the requirement).
Thank you.
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I have used Jhipster to develop quite a few applications however today I run into a little problem and it is how to configure Transaction Routing Datasource in Jhipster. I am using Kubegres to set up a Postgresql server with multiple read replicas and one write replica. I have configured a project to use Spring's Transaction Routing Datasource and I have succeeded in configuring it, but when I try to do the same configuration with Jhipter for another project and although I manage to get it to run without problems, it does not route for read-only replicas. Has anyone had the same problem and managed to get it to work
I am trying to understand the transaction management in Spring, and I have got some doubts.
I read a bit about transaction management in EJB world, which can be CMT or BMT. For CMT, as per the documentation, it is Application server (e.g. JBOSS) which manages the transaction.
Now, coming to Spring transaction management, and considering using Web container only (Apache Tomcat), how does this work?
Does Spring have its own transaction management with capability of handling local transaction and global transaction (which works with 2 phase commit). Do the actual support need to come by the underlying container (in this case Apache tomcat) or support from framework is sufficient?
I am not clear how all these pieces fit together.
Can anyone help me understand this?
Spring doesn't include any kind of transaction capability of its own, it only provides ways to connect to transaction functionality provided by the container or by standalone libraries.
If you run your application on Tomcat and don't provide any transaction manager libraries like bitronix, then you get only local jdbc transactions provided by the servlet container.
When you read the bullet points at https://docs.spring.io/spring/docs/4.2.x/spring-framework-reference/html/transaction.html notice it says spring is providing abstractions, that means it is providing access through its own apis and using aop to make transactions nonintrusive, but not providing any implementation of transactional functionality. It's facilitating gluing things together, which is the main thing spring does.
I have a running Spring application that already works on Weblogic and JBoss, and I'm adding the option to run it by itself with Spring Boot.
As it has a Java EE architecture, it has a container-managed datasource that is looked up by a JNDI name, and I wanted to keep it that way.
I see that Spring Boot has the ability to use a EE container called Undertow, that it turns out to be the Wildfly EE engine.
I've done A LOT of research on how to define this JNDI Datasource in Undertow with config files and stuff, but I can't find any documentation on that on Undertow's website and neither on WildFly documentation.
Has someone already done that? I need to know how to define this Datasource with a config file or something.
I don't think Undertow supports that - it's just a web server, nothing else, and very far from being a JEE container. Wildfly, on the other hand, is a JEE container and it uses Undertow as a web engine and builds up other JEE stuff around it.
Here's a quote from Undertow's official documentation:
On thing that makes Undertow unique is that it has no concept of a global container. Instead an Undertow server is assembled by the embedding application. This makes Undertow extremely flexible, and the embedding application can basically just pick the parts that they need, and assemble them in whatever way makes sense.
An Undertow server is basically composed of three things, one (or more) XNIO worker instance, one or more connectors, and a handler chain to handle incoming requests.
Need to call a EJB service from the servlet context listener's contextInitialized() method. Application is running on JBOSS, though the context listener works fine, I'm not able to access the EJB bean through JNDI look up.
Because the web deployment in JBOSS happens before EJB beans are bound with JNDI tree. How to overcome from this? Is there a way to configure JNDI bind early or start the web deployment later once EJB's are completely deployed?
I had put Thread.sleep() before the service call in the contextInitialized() method, it is working fine in my JBoss5.1.0 GA, and the same did not work in other machines JBoss of same version.
Applications needs this because, we want to load some master data from the DB and make it available in the web layer (kind of caching). Does JBOSS startupmbean suit this requirement? If yes how can I make the data available to web layer?
Also if any alternative ways are available, please suggest.
Poll for the EJBs in contextInitialized(). So instead of just sleeping for a certain time, try to connect to the EJB. If that fails, sleep, and retry, until the EJBs are available. In this case the context initialization is blocked.
Implement the cache as a lazy one: Fill the cache during the first query (and use the same polling procedure: connect to the EJB, retry until it becomes available). In this case the cache blocks.
You could split your deployment into two parts: One for the EJBs, one for the web application. Then deploy the first, and delay deployment of the web application until the EJBs are bound (either by watching the log file or by trying bind to the EJB from a command line app)
our prod environment architecture is decided to be like this:
2 machines that each of them have 2 tomcat instances (on vm). there is spring web app with hibernate running on tomcat.
there are also 2 db instances distributed to both machines.
so, we think that hazelcast fits this achitecture well. hazelcast will be second level cache for hibernate, it will manage clustered cache over db instances.
we installed hibernate server and defined our clusters on it.
i've searched offical hazelcast doc and several sites but i couldnt find the way to configure hibernate to use this hazelcast server as L2 cache.
we dont want to change our existing app. we'll keep using hibernate as it is. is it possible? if so, how we can configure hazelcast server on our web app?
I think it is important to understand that your probably don't want to have a standalone Hazelcast cluster/server; what you normally do is to embed Hazelcast within your application.
Like Miko said, you can just enable Hazelcast to be used as second level cache; no need to make any fundamental changes.
I also don't understand what you mean with 'hibernate server', because Hibernate is just an OR mapper library and has no concept of server.
So can you tell a bit more what you want so we can help you out?