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Ensure zero downtime

Fernando Franzini
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Joined: Jan 09, 2009
Posts: 486
    
    2

Hello Ranchers
My assignment has no information about traffic, number of enabled users and number of simultaneous user expected. The only explicit requirement is the availability. To ensure this all I design a clustered architecture with high availability. My concern now is related to the update time solution (redeploy). How could I update the solution without interrupting service? From what I understand today, I believe that is using proprietary extensions application server. Can someone help me with any tips?
Best Regards.


Fernando Franzini - Java Blog
Rajeev Rnair
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Joined: Mar 22, 2010
Posts: 308

Hi Fernando, all most all application servers provide options for HOT deployment so that you do not need to restart app server after a deployment
For example in J Boss AS, you only need to copy EAR or WAR file to the deploy folder, which will deploy the application automatically
For web services (Spring) redeployment on a Linux server, I normally kill the current process, copy the JAR files, and run the shell script to start the service
For high availability, app / db servers can be load balanced and clustered. You can use different RAID solutions for database servers / app servers etc. If one disk fails, next one picks up automatically
Also consider virtual servers using VMWare etc where there will be a host server and multiple guest servers.
Think about backups of virtual servers. Also scheduled hot / cold backups of databases
Good luck!


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Fernando Franzini
Ranch Hand

Joined: Jan 09, 2009
Posts: 486
    
    2

all most all application servers provide options for HOT deployment so that you do not need to restart app server after a deployment
For example in J Boss AS, you only need to copy EAR or WAR file to the deploy folder, which will deploy the application automatically

But that will stop solution for a few seconds losing active sessions from users. They need to re-authenticate....

For high availability, app / db servers can be load balanced and clustered. You can use different RAID solutions for database servers / app servers etc. If one disk fails, next one picks up automatically
Also consider virtual servers using VMWare etc where there will be a host server and multiple guest servers.
Think about backups of virtual servers. Also scheduled hot / cold backups of databases

OK....
Rajeev Rnair
Ranch Hand

Joined: Mar 22, 2010
Posts: 308

Fernando Franzini wrote:
But that will stop solution for a few seconds losing active sessions from users. They need to re-authenticate....
Not necessarilly, we do that for applications in JBoss which is authentcated by Tivoli Access Manager and it doesnt force users to re login
never tried in OAS though. we get a maintenance window and we use that for deployments etc even though it is a 24x7 app

Jeanne Boyarsky
author & internet detective
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Joined: May 26, 2003
Posts: 30596
    
154

Read up on "five nines". Literal 100% availability is prohibitively expensive. Coming close is what you want.


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Fernando Franzini
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Joined: Jan 09, 2009
Posts: 486
    
    2

Jeanne Boyarsky wrote:Read up on "five nines". Literal 100% availability is prohibitively expensive. Coming close is what you want.

very interesting .. I had never heard about it.
Regards Jeanne.
Fernando Franzini
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Joined: Jan 09, 2009
Posts: 486
    
    2

My assignament says "Availability is critical.....is must be available 24 hours a day during the week".
Do you think "five9s" is enough to solve this?
Jeanne Boyarsky
author & internet detective
Marshal

Joined: May 26, 2003
Posts: 30596
    
154

24 hours a day during the week is different than 24x7. You could be down 48 hours a week and still meet their criteria! An important thing to think about when designing.
Fernando Franzini
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Joined: Jan 09, 2009
Posts: 486
    
    2

24 hours a day during the week is different than 24x7

Could you explain why is different
Regard.
Jeanne Boyarsky
author & internet detective
Marshal

Joined: May 26, 2003
Posts: 30596
    
154

Fernando Franzini wrote:
24 hours a day during the week is different than 24x7

Could you explain why is different
Regard.

Because with the first I can have 10 hours of downtime on the weekend to deploy, take backups, have the system take a nap, whatever. But with the second one I can't do that.
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: Ensure zero downtime