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Difference between revisions of "Heat/Blueprints/ScalableResourceGroup"

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     Initial number of resources in the group at creation time.
 
     Initial number of resources in the group at creation time.
 
     Optional property, defaults to 1.
 
     Optional property, defaults to 1.
 +
    The value must be at least 0.
  
 
     max_size: Integer
 
     max_size: Integer
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     Optional Property, defaults to 1.
 
     Optional Property, defaults to 1.
 
     Updates can cause creation/deletion of some resources according to scale_in_criteria/scale_in_order.
 
     Updates can cause creation/deletion of some resources according to scale_in_criteria/scale_in_order.
 +
    The value must be at least 0.
  
 
     min_size: Integer
 
     min_size: Integer
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     Optional property, defaults to 1.
 
     Optional property, defaults to 1.
 
     Updates can cause addition/removal of resources according to scale_in_criteria/scale_in_order.
 
     Updates can cause addition/removal of resources according to scale_in_criteria/scale_in_order.
 +
    The value must be at least 0, less than or equal to max_size.
  
 
   scale_in_criteria:String
 
   scale_in_criteria:String
   Specifies criteria for removal of resources form the group.
+
   Removal criteria of resources in the group.
 
   Optional property, defaults to "Index".
 
   Optional property, defaults to "Index".
 
   Possible Values: "Index" or "Age"
 
   Possible Values: "Index" or "Age"
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   scale_in_order:String
 
   scale_in_order:String
   Specifies order for removal of resources form the group according to the specified criteria.
+
   Removal order of resources in the group according to the specified criteria.
 
   Optional property, defaults to "Decreasing".  
 
   Optional property, defaults to "Decreasing".  
 
   Possible Values: "Increasing" or "Decreasing"
 
   Possible Values: "Increasing" or "Decreasing"

Revision as of 15:32, 10 August 2015

< Heat Launchpad Entry: HeatSpec:ScalableResourceGroup
Created: 26 July 2015
Contributors: Ahmed El-Khouly

Summary

OS::Heat::ResourceGroup provides a way to create several instances of identically configured nested resource; resources within the group can be addressed with their resource index.
OS::Heat::ResourceGroup can only scale by changing the count property followed by a stack update of the root stack.
OS::Heat::AutoScalingGroup/Policy also provide a way to create several instances identically configured nested resources with the added ability of changing size(scale) when the accompanying AutoScalingPolicy receives a signal. Auto-scaling policy defines characteristics of the scale operation (size of adjustment, size of adjustment, cool down period).

Some cloud applications need a resource group type that can change size and with the added ability of removal or addition of specific resources.


Release Note

TBD

Rationale

Some cloud applications need a new resource group with the following features:
1) Create an initial number of identically configured nested resources.
2) Address single resource within the group using the index with the ability to specify a variable to be replaced by the index.
3) Add(Remove) specific resource within the group by specifying the indices of involved resources.
4) Scale out(in) by adjusting the group size (with a certain increment) when user defined triggers are met.

User Stories

1) Recreate a (failed) resource by adding/deleting the corresponding nested resource in the group.
2) Add new resources to group when certain criteria met(ex. increase in workload).
3) Remove a number of resources according to a predefined criteria(increasing or decreasing order of age or index).
4) Specify certain resources for removal.

Assumptions

None.

Design

Define a new heat resource type: OS::HEAT::ScalableResourceGroup with the following properties:

   resource_def : Map
   Resource definition for the resources in the group. 
   Required property.
   Can be updated without replacement.
   index_var : String
   A variable that this resource will use to replace with the current index of a given resource in the group. 
   Updates cause replacement.
   Optional property, defaults to “%index%”.
   initial_size: Integer
   Initial number of resources in the group at creation time.
   Optional property, defaults to 1.
   The value must be at least 0.
   max_size: Integer
   Maximum number of resources in the group.
   Optional Property, defaults to 1.
   Updates can cause creation/deletion of some resources according to scale_in_criteria/scale_in_order.
   The value must be at least 0.
   min_size: Integer
   Minimum number of resources in the group.
   Optional property, defaults to 1.
   Updates can cause addition/removal of resources according to scale_in_criteria/scale_in_order.
   The value must be at least 0, less than or equal to max_size.
  scale_in_criteria:String
  Removal criteria of resources in the group.
  Optional property, defaults to "Index".
  Possible Values: "Index" or "Age"
  Default: "Index"
  scale_in_order:String
  Removal order of resources in the group according to the specified criteria.
  Optional property, defaults to "Decreasing". 
  Possible Values: "Increasing" or "Decreasing"
  Default: "Decreasing"

ScalableResourceGroup class inherits from ResourceGroup:

   - Provide handle_signal implementation to receive signals to add/delete and grow/degrow signals.
   - Override create/validate/update/delete handlers.