Update APMEC code
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Tung Doan
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doc/source/user/scale_usage_guide.rst
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doc/source/user/scale_usage_guide.rst
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..
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Licensed under the Apache License, Version 2.0 (the "License"); you may
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not use this file except in compliance with the License. You may obtain
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a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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License for the specific language governing permissions and limitations
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under the License.
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.. _ref-scale:
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===========
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MEA scaling
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===========
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MEA resources in terms of CPU core and memory are hardcoded in MEAD template
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through image flavor settings. This result in either provisioning MEA for
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typical usage or for maximum usage. The former leads to service disruption
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when load exceeds provisioned capacity. And the later leads to underutilized
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resources and waste during normal system load. So apmec provides a
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way to seamlessly scale the number of MEAs on demand either manually or
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automatically.
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TOSCA schema for scaling policy
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Apmec defines TOSCA schema for the scaling policy as given below:
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.. code-block:: yaml
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tosca.policies.apmec.Scaling:
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derived_from: tosca.policies.Scaling
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description: Defines policy for scaling the given targets.
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properties:
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increment:
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type: integer
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required: true
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description: Number of nodes to add or remove during the scale out/in.
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targets:
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type: list
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entry_schema:
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type: string
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required: true
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description: List of Scaling nodes.
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min_instances:
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type: integer
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required: true
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description: Minimum number of instances to scale in.
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max_instances:
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type: integer
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required: true
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description: Maximum number of instances to scale out.
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default_instances:
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type: integer
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required: true
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description: Initial number of instances.
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cooldown:
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type: integer
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required: false
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default: 120
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description: Wait time (in seconds) between consecutive scaling
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operations. During the cooldown period, scaling action will be ignored
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Sample TOSCA with scaling policy
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Following TOSCA snippet shows the scaling policy used in MEAD, in which vdu1
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and vdu2 are already defined VDUs.
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.. code-block:: yaml
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policies:
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sp1:
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type: tosca.policies.apmec.Scaling
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description: Simple VDU scaling
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properties:
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min_instances: 1
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max_instances: 3
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default_instances: 2
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increment: 1
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targets: [vdu1, vdu2]
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Deploying scaling TOSCA template using Apmec
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Once OpenStack/Devstack along with Apmec has been successfully installed,
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deploy a sample scaling template from location given
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below:
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https://github.com/openstack/apmec/tree/master/samples/tosca-templates/mead
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Refer the 'Getting Started' link below on how to create a MEAD and deploy a
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MEA:
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https://docs.openstack.org/apmec/latest/install/getting_started.html
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How to scale MEA using CLI
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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Apmec provides following CLI for scaling.
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.. code-block::console
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**apmec mea-scale --mea-id <mea-id>**
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**--mea-name <mea name>**
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**--scaling-policy-name <policy name>**
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**--scaling-type <type>**
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Here,
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* scaling-policy-name - Policy name defined in scaling MEAD
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* scaling-type - in or out
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* mea-id - scaling MEA id
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* mea-name - scaling MEA name
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For example, to scale-out policy 'sp1' defined above, this cli could be used
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as below:
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.. code-block::console
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**apmec mea-scale --mea-name sample-mea**
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**--scaling-policy-name sp1**
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**--scaling-type out**
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How to scale MEA using REST API
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Apmec provides following REST API for scaling.
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**POST on v1.0/meas/<mea-id>/actions**
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with body
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.. code-block::json
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**{"scale": { "type": "<type>", "policy" : "<scaling-policy-name>"}}**
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Here,
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* scaling-policy-name - Policy name defined in scaling MEAD
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* scaling-type - in or out
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* mea-id - scaling MEA id
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Response http status codes:
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* 202 - Accepted the request for doing the scaling operation
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* 404 - Bad request, if given scaling-policy-name and type are invalid
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* 500 - Internal server error, on scaling operation failed due to an error
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* 401 - Unauthorized
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MEA state transitions during scaling operation
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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During the scaling operation, the MEA will be moving in below state
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transformations:
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* **ACTIVE -> PENDING_SCALE_IN -> ACTIVE**
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* **ACTIVE -> PENDING_SCALE_IN -> ERROR**
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* **ACTIVE -> PENDING_SCALE_OUT -> ACTIVE**
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* **ACTIVE -> PENDING_SCALE_OUT -> ERROR**
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Limitations
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~~~~~~~~~~~
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Following features are not supported with scaling:
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* Auto-scaling feature is supported only with alarm monitors and it does
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not work with other monitors such as ping, http_ping.
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* When MEA is modelled with scaling requirement in MEAD, any config
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management requirement in MEAD is not supported.
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* Scaling feature does not support to selectively choose the VDU as part
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of scaling.
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