Application instance reassignment in DEA's on deleting DEA

[Wahaj Ali]

When removing a DEA via BOSH, what exactly is the process for reassigning the applications instances that were running on this DEA to some other DEAs. Is that handled completely separately via the Cloud Foundry health monitor (for example once it detects the application instances that are down) or is there some other process? 

Thanks

Wahaj

[James Bayer]

when a DEA is being shut-down, if it is BOSH deployed, there is a hook to call the deterministic drain script [1].

even if a DEA is shut down harshly, the health manager should take over and coordinate with the cloud controller to restore all app instances that were running on that DEA on available DEA's, it just may not be as smooth/fast if it's not done with the drain script, which sends signal USR2 to the PID of the DEA.

[1] https://github.com/cloudfoundry/cf-release/blob/master/jobs/dea_next/templates/deterministic_drain.rb

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Thank you,

James Bayer

[wulo...@huawei.com]

Hi James,

The drain script just kills the process of DEA, I don't understand why it can restart app on another DEA?

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Regards
Tim

[Ferran Rodenas]

It's the CF health manager who detects that there're missing apps (because the DEA has been stopped), and then sends a message to the cloud controller, who deploys again the apps on another available DEA.

This blog post by Cornellia explains all the available HA mechanisms: http://blog.gopivotal.com/cloud-foundry-pivotal/products/the-four-levels-of-ha-in-pivotal-cf

- Ferdy

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