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Instance HA

asked 2014-08-21 00:36:52 -0600

Vidhyut gravatar image

Suppose a running instance (attached to a volume) goes down for some reason. I want a duplicate instance to come up with the same IP and the same volume attached to it. How do I make this happen ?
PS : I have enabled Orchestration in the cloud.

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can you refer to this blog:

SGPJ gravatar imageSGPJ ( 2014-08-21 06:04:15 -0600 )edit

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answered 2014-08-21 10:07:35 -0600

mpetason gravatar image

You could use Orchestration to ensure that an instance is available and use LBaaS to load balance between instances. You would still need some type of monitoring. Your scenario also depends on a few situations. Are the instances presenting static information or is it a DB type back-end that you want HA?

If it's static you could:

Stand up multiple instances with the same information and have multiple volumes. Setup LBaaS. Load balance between those instances. If one of the instances fails have monitoring setup. You'll have to script (or build logic into orchestration) a way for the failed instance to be deleted then a new one stood up in it's place and attached to the volume. Remove Attachment > Delete > Create > Re-attach > Update Pool in LBaaS. In this scenario you aren't actually worried about the IP address of the instance, since everything is accessing it over the VIP.

If it's not static :

With a DB back-end type scenario you need to build a lot more logic in. Or you could just have monitoring setup which triggers api calls to remove the instance/add a new one. In this scenario you still need to use a Floating IP address and have the front end access the DB over the Floating IP, even if it's in the same network. Otherwise you are going to have more difficulty trying to get the same IP address. Remove Attachment > Delete > Create > Reattach > Reassign IP. You have to build in logic to make sure you get some of the information before you delete the instance, such as what IP address it is using for it's Floating IP.

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My instances run RHEL5 OS. The instances present static information. I want to build logic into orchestration as you suggested. Please provide some pointers.

Vidhyut gravatar imageVidhyut ( 2014-08-21 23:36:16 -0600 )edit

CDOT - You will want to look into ceilometer alarms + heat. You'll need to look at templates for Heat, find LBaaS type options.

mpetason gravatar imagempetason ( 2014-08-28 12:56:14 -0600 )edit

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Asked: 2014-08-21 00:36:52 -0600

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Last updated: Aug 21 '14