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interview question: how do you know which server is being used in multiserver app during production?

 
Madhu Pendy
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Hello,

I have been asked a question during an java developer interview.
how do you identify which server the application is using during production issue in a multi server environment?
ex: lets take Amazon has several servers, there is an production issue, to address that issue where do you check, where you start your digging about the issue.

I googled for an answer did not get any to the point answer. Please throw some light.

thanks
 
Maneesh Godbole
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Welcome to the Ranch.

I re read your question multiple times and it still does not make sense to me.
Several servers? As on application server, DB server etc? Or several nodes deployed behind some load balancer.
 
Madhu Pendy
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hi Maneesh,
its several nodes deployed behind some load balancer.
 
Jayesh A Lalwani
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What does the load balancer do?
 
Madhu Pendy
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at very external level - load balancer is , when there is heavy flow of requests , few requests will be transferred to another server(node) to address the request.
 
Ivan Jozsef Balazs
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It seems to depend on the load balancer and its settings.

For example sticky sessions are conceivable, that is, once a HTTP session was established, it will be served by the same instance.
 
Shankar sanjay
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Hi,

We had the same kind of requirement, we use to print the server details in log file itself. However we were using WAS 6.1 App Server, and WAS 6.1 provide some lib to get the server details.

In simple way, you can add/print the server details in request listener itself, using request.getLocalName() or InetAddress.getLocalHost().getHostName()
 
Winston Gutkowski
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Madhu Pendy wrote:at very external level - load balancer is , when there is heavy flow of requests , few requests will be transferred to another server(node) to address the request.

That wasn't Jayesh's question - and I suspect he already knows what a load-balancer's function is in general terms.

My problem is that I'm still not quite sure what your question is: At the elemental level, a data packet usually contains a source IP address; but there are all sorts of mangling processes like NAT that may obscure it from you, so without some knowledge of what those are, it may be quite difficult to track a problem back to its identifying "server".

Perhaps you could give us some more information on what this interview question was all about?

Winston
 
Jeanne Boyarsky
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I think this is a troubleshooting question. How do you know there is a production issue? How do you know it has something to do with one of the servers/ My guess is there would be something in the logs on that server to give a clue.

It's ok to answer a question with more questions.
 
Amit Ghorpade
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Well if a particular node is down, the load balancer UI will point that out.
If the interviewer meant without looking at the load balancer, I would say its not worth beating around the bush in a production environment.
 
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