If I understand correctly the default JNDI service runs on my local AS, right? So if I create an EJB and in jboss.xml (running JBoss) I name it "sth" than it is registered in my AS. Correct?
In big projects EJBs might be distributed through many servers - on one server EJBs doing sth and on another sth else. When calling JNDI loopup() I search only one server, right? So it means that I need to know where the EJB is registered... Is it true?
When you cluster your app you will usually configure the cluster so that you have one shared JNDI. In JBoss you do this using HA-JNDI (High Availability - JNDI) or equivalent. This is a centralized service with fail-over. In principle you could imagine having a replicated service for better throughput, but to my knowledge that is not available in JBoss.
In short, you will have only one namespace, so you don't need to know where it is registered.
Related
I have a number of demo environments that I would like to setup for different groups of customers. These would contain the same deployment apps (WAR's) but requiring different configurations. currently I'm using:
3 datasources (accessed by JNDI) per application (so each environment would need different databases)
some Naming/JNDI simple bindings which would need to be different by environment.
one activeMQ queue for environment, also identified via JNDI.
Would it be possible, on Wildfly 11, to configure the Naming, Datasources and ActiveMQ subsystems on a non-global manner ? Maybe by either configuring the subsystems on a server, host or deployment level? I don't mind having multiple Server or Hosts definitions with different network ports (8080, 8081, etc...)
I know that I can setup multiple instances of standalone running on the same machine, each with a different configuration file, but I would realy like to use the same Wildfly instance to manage this scenario. Is this at all possible ?
Thank you,
You should be using domain mode where you can manage several servers and assign to them different configuration profile https://docs.jboss.org/author/display/WFLY/Domain+Setup
I am new to Spring Cloud. Currently, I want to build a new micro service based on Spring Cloud. It is very easy to build a new Eureka server. But my question is that how to make it high availability ? For example I create two Eureka server and a load balancer. When one of the Eureka server is down, the system still works well. But I don't know to to consist registered information in the two Eureka server.
I have already asked something similar in the spring cloud gitter channel.
Because of the CAP theorem, something as a distributes Service discovery has to decide, either to provide availability, or more consistency, with a trade off to the other one.
in short, by quoting Spencer Gibb:
Eureka favors availability over consistency
so it is very available, while registred services may be not acutal anymore.
As Spencer suggested, if consistency is something you need more then availability, try Consul together with spring cloud consul intead
I am trying to get a list of the queue names and jndi names in java. I have tried using pcf and have only been able to get queue names. The documentation on the IBM sight has not been too helpful.
MQ Java PCF classes can be used to do a number of tasks like inquiring list of queues, channels etc. Also Add/Update/Delete number of queue manager objects can be done. But PCF classes can not be used inquiring JNDI names. JNDI names must be retrieved from a JNDI store like File/LDAP/J2EE JNDI and not in MQ queue manager.
HTH
Since your inquiry was tagged WebSphere, I'll assume some version of WebSphere Application Server (WAS). WAS includes a utility called dumpnamespace. Run it with the -h option to list its options. Aim it at your bootstrap port and it should do as its name implies.
I have 2 instances of Jboss servers running on eg: 127.0.0.1 and 127.0.0.2.
I have implemented Jboss load balancing, but am not sure how to achieve server failover. I do not have a webserver to monitor the heartbeat and hence using mod_cluster is out the question. Is there any way I can achieve failover using only the two available servers?
Any help would be appreciated. Thanks.
JBoss clustering automatically provides JNDI and EJB failover and also HTTP session replication.
If your JBoss AS nodes are in a cluster then the failover should just work.
The Documentation refers to an older version of JBoss (5.1) but it has clear descriptions of how JBoss clustering works.
You could spun up another instance to server as your domain controller, and the two instances you already have will be your hosts. Then you could go through the domain controller, and it will do the work for you. However, I haven't seen instances going down to often, it usually servers that do, and it looks like you are using just one server (i might be wrong) for both instances, so i would consider splitting it up.
I am thinking about porting a Spring Quartz based application to EJB 3.1 to see if EJB has improved. I am having problems understanding how fail-over works with the Schedule Timer Service. In Quartz, there are database tables which clustered Quartz instances use. If one node in your cluster crashes, jobs will still get executed on other nodes.
I have been looking at how the Timer Service persists things and it appears to use the file system of the server the Timer was created on. Is this true? I do not see how this would be possible as it would render the Timer Service unusable since it would not support failover.
So i must be missing something. Can anyone help me out with this?
The EJB timer service is simply not as advanced as Quartz (with or without Spring).
EJB timers are persisted to an unknown location. It may happen to be the file-system, but it could also be the Windows registry if you happen to be running on Windows, or it could be an LDAP server or whatever.
There was an issue on the EJB spec JIRA for some time about this, and it was discussed on the spec mailing list, but then it was brutally dropped and closed because no one bothered to reply anyone (perhaps because a lot of people were on vacation at the time). It's one of the lamest reasons to close an issue if you'd ask me, but I guess the spec lead sometimes must resort to such measures.
Anyway, in JBoss AS persisting happens to an embedded relational datasource, that on its turn writes to the filesystem. Via propriatary configuration you can point this datasource to any remote DB. Fail-over would have to come from propriatary JBoss functionality as well. Although EJB forbids lots of things for the sake of potential clustering, there's no explicit clustering support in the spec and thus specifically EJB timers are not cluster aware.
Not sure if this was available at the time of the question but you can use the 'cluster-ha-singleton' for this, it allows you to create a singleton timer that is invoked from a single cluster node, in case of failover of the chosen node a new node is elected to run the singleton (and therefore the timers)
http://www.jboss.org/quickstarts/eap/cluster-ha-singleton/
It mentions EAP but I am running on AS 7.2.0 fine, the jars are already included in /modules/org/jboss/