[Clustering/JBoss] - Re: Load Balancing?
by bstansberryï¼ jboss.com
I can edit my posts; I don't know if that comes with admin powers or something?
Anyway, AIUI, you're talking about some sort of front-end load balancer that balances calls to a series of Apache/mod_jk boxes, each of which manages a subset of AS instances, balancing to those. Any session replication only occurs within that subset. Correct?
Question here, is do the mod_jk instances know about all the AS instances, or just a subset? I.e., say you have 100 AS instances and 10 mod_jk; does each mod_jk only know about 10 AS instances, or 100?
If each mod_jk only knows about 10, you have a problem. If for whatever reason a session becomes unstuck on the front-end load balancer (say mod_jk #1 fails, or there's a flaw in the sticky session handling on the front end), then a request could go to any of the mod_jk instances. If that mod_jk doesn't know how to reach the subset of AS' that have the sessions, the session is lost.
So, each mod_jk has to know about all AS instances.
Next issue is how to ensure that if there is a failover at the AS level that the AS instance mod_jk picks is in the same subset as the original AS. Has to be in the same subset or the failover AS won't have a copy of the session.
To do that, you can use mod_jk's 'domain clustering' feature. (Only do the following with mod_jk 1.2.19 or later; before that the session stickiness didn't work right.)
Say you have 4 workers in workers.properties, named node1 ... node4. You want to group them into 2 groups, group1 and group2. On the AS nodes, the sessions are only replicated within those groups.
In workers.properties, add:
worker.node1.domain=group1
worker.node2.domain=group2
worker.node3.domain=group3
worker.node4.domain=group4
In the server.xml file on both node1 and node2, set the jvmRoute="group1" instead of "node1" and "node2". On node3 and node4 use "group2".
If you use this, mod_jk will ensure your session stays within the set of "groupX" nodes if a failover occurs.
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18Â years, 6Â months
[JBoss jBPM] - Job at top investment bank in NYC for JBoss Rules jBPM devel
by brianspagat
My name is Brian Spagat and I can be reached at 212-6775-1116. Here is the role.
Summary:
The Ordering and Fulfillment group is responsible for developing a global platform to manage the entry, validation, routing, and execution of requests for technology related products and services. This involves developing a set of core modules that are reliable and recoverable as well as gateways to existing inventory and fulfillment systems.
Principal Responsibilities:
Managing a small team of developers.
Participation in module design
Development of modules
Experience/Skills:
3-10 years of experience
Strong jBPM skills are required.
Strong Java Development skill are required.
Knowledge of JBOSS and JBOSS Rules a plus.
Adequate knowledge of SQL and RDBMS.
Database skills in UDB a plus
Experience developing in a Linux/Unix environment
Good communication/interpersonal skills/highly motivated.
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18Â years, 6Â months
[JBossCache] - Re: Transactions
by manik.surtaniï¼ jboss.com
Hi
The differences are that approach 1 treats C as a store of data. Approach 2 treats C as a peer.
Even with approach 1, data changes in C will be picked up by B if the node didn't already exist in B or if the node was evicted. So if your requirement isn't for changes in C to be seen in B *in real time*, then an eviction policy on B will ensure that changes are seen up to a certain delay.
With approach 2, you shouldn't have too much information if all the state in C is relevant to B.
Re: your question on txs, this will still work since changes to the TcpCacheLoader are written in 2 phases as well, a prepare and commit phase and only when B1 or B2 successfully commits will the TcpCacheLoader be instructed to commit changes.
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18Â years, 6Â months