I am trying to add clustering to my application which uses Jboss server. For replication session,
I have added <distributable/> tag in web.xml. But, I get following warning and session replication seems to be not working. Please suggest the best way to handle session replication for Jboss.
Warning:
Failed to setup clustering, clustering disabled. NoClassDefFoundError: org/jboss/cache/pojo/jmx/PojoCacheJmxWrapperMBean
Server : Jboss 5.1
Load balance implemented by mod_jk.
Is it possible that you are not using a JBoss profile that has clustering related services? I believe the "default" profile does not have the clustering capabilities. You have to use the "all" profile to have the clustering capabilities.
JBoss_HOME
|
|---> bin
|---> client
|...
|---> server
| |---> default (clustering not enabled)
| |---> all <== (clustering enabled)
|...
Related
Can you please suggest some of the industry best practices (of the type "it depends") to deal with a WAR (web application archive) deployed into a J2EE container to connect with a RDBMS?
In the current scenario, we deploy the .war file to an Apache Tomcat instance that connects to a PostgreSQL data base instance. We are required to scale up both in terms of data storage and transactions (multi read-write).
It seems, we have two choices.
Build load balancing system
First, we start with Apache Tomcat clustering as described here with a short graphic (from their website) as below.
DNS Round Robin
|
Load Balancer
/ \
Cluster1 Cluster2
/ \ / \
Tomcat1 Tomcat2 Tomcat3 Tomcat4
Then, build the database cluster as described here whose graphic is shown below.
Both clustering (Tomcat and PostgreSQL) are front-ended by HAProxy as shown in the graphic below.
Use IaaS provider
Or, perhaps, just set-up the servers in AWS and let AWS manage all balancing while we just pay per use. For example, as described here for a typical set-up and here for AWS PostgreSQL.
jBoss EAP 6.2 supports full and full-ha profiles (amongst others). In standalone deploy, we use domain mode with full profile for an app.
App that we have is primarily having/exposing RESTful services which are stateless - there is a administration web portal, but it is ok to not have session replication for this (i.e. if one server goes down, it is acceptable for users to lose the browsing session and login again). app does not make use of EJBs.
In deployment, if we have a hardware loadbalancer that is able to route requests to nodes in active-active mode, then, is it ok to just go with full profile on nodes and not use the full-ha profile ? or is there a benefit to be got from using the full-ha profile? using the former approach simplifies deployment and makes spinning up a new VM with the app relatively easier.
Any inputs/directions/pointers in this regard would be most useful.
The used JBoss profile depends on what you need from it. standalone-full-ha provides Infinispan, Web-Session and HornetQ (JMS) replication whereas standalone-ha provides no JMS.
You can run active-active clusters with load balancers in front with the standalone profile as long as you do not replicate data/states using JGroups, Infinispan and so on.
Got a general question about load balancing setup in JBoss (7.1.1.Final). I'm trying to setup a clustered JBoss instance with a master and slave node and I'm using the demo app here (https://docs.jboss.org/author/display/AS72/AS7+Cluster+Howto) to prove the load balancing/session replication. I've basically followed through to just before the 'cluster configuration' section.
I've got the app deployed to the master and slave nodes and if I hit their individual IPs directly I can access the application fine. According to the JBoss logs and admin console the slave has successfully connected to the master. However, if I put something in the session on the slave, take the slave offline, the master cannot read the item that the slave put in the session.
This is where I need some help with the general setup. Do I have to have a separate apache httpd instance sat in front of JBoss to do the load balancing? I thought there was a load balancing capability built into JBoss that wouldn't need the separate server, or am I just completely wrong? If I don't need apache, please could you point me in the direction of instructions to setup the JBoss load balancing?
Thanks.
Yes, you need a Apache or any other software or hardware that allows you to perform load balancing of the HTTP request JBoss Application Server does not provide this functionality.
For proper operation of the session replication you should check that the server configuration and the application configuration is well defined.
On the server must have the cache enabled for session replication (you can use standalone-ha.xml or standalone-full-ha.xml file for initial config).
To configuring the application to replicate the HTTP session is done by adding the <distributable/> element to the web.xml.
You can see a full example in http://blog.akquinet.de/2012/06/21/clustering-in-jboss-as7eap-6/
I have a free OpenShift account with the default 3 gears. On this I have installed the WildFly 8.1 image using the OpenShift web console. I set the minimal and maximal scaling to 3.
What happens now is that OpenShift will create 3 JBoss WildFly instances:
One on the entry node (which is also running HAProxy)
One on an auxiliary node
One on another auxiliary node
The weird thing is that the JBoss WildFly instance on the entry node is by default disabled in the load balancer config (haproxy.conf). BUT, OpenShift is still deploying the war archive to it whenever I commit in the associated git repo.
What's extra problematic here is that because of the incredibly low number of max user processes (250 via ulimit -u), this JBoss WildFly instance on the entry node cannot even startup. During startup JBoss WildFly will throw random 'java.lang.OutOfMemoryError: unable to create new native thread' (and no, memory is fine, it's the OS process limit).
As a result, the deployment process will hang.
So to summarize:
A JBoss WildFly instance is created on the entry node, but disabled in the load balancer
JBoss WildFly in its default configuration cannot startup on the entry node, not even with a trivial war.
The deployer process attempts to deploy to JBoss WildFly on the entry node, despite it being disabled in the load balancer
Now my question:
How can I modify the deployer process (including the gear start command) to not attempt to deploy to the JBoss WildFly instance on the entry node?
When an app scales from 2 gears to 3, HAproxy stops routing traffic to your application on the headgear and routes it to the two other gears. This assures that HAproxy is getting the most CPU as possible as the application on your headgear (where HAproxy is running) is no longer serving requests.
The out of memory message you're seeing might not be an actual out of memory issue but a bug relating to ulimit https://bugzilla.redhat.com/show_bug.cgi?id=1090092.
I am trying to find a list of all the possible 'System' keyspaces that MAY exist in a DSC Cassandra database (System keyspaces are those which are not created by a user).
My experience thus far is I have found
[cqlsh 3.1.8 | Cassandra 1.2.15 | CQL spec 3.0.0 | Thrift protocol 19.36.2]
system system_traces OpsCenter
Are these the only available System Keyspaces or are there others? Does it depend on the version(1.2/2.0) and distribution(Apache/Datastax)?
I tried to search the documentation but no luck. Could anyone help me out here?
Only system, system_auth and system_traces are strictly "System", especially the 1st one.
OpsCenter is created for/by DataStax OpsCenter