Initial draft of compute driver spec
Address comments by TrevorV, and fix tabification. Try to make doc8 happy. Change-Id: Ida4aef02578cea7e2e76c9106c94d4ef633c06d6
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Al Miller
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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==========================================
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Compute Driver Interface
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==========================================
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https://blueprints.launchpad.net/octavia/+spec/compute-driver-interface
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This blueprint describes how a driver will interface with Nova to
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manage the creation and deletion of amphora instances. It will
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describe the base class and other classes required to create, delete,
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manage the execution state, and query the status of amphorae.
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Problem description
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===================
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The controller needs to be able to create, delete, and monitor the
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status of amphora instances. The amphorae may be virtual machines,
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containers, bare-metal servers, or dedicated hardware load balancers.
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This interface should hide the implementation details of the amphorae
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from the caller to the maximum extent possible.
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This interface will provide means to specify:
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- type (VM, Container, bare metal)
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- flavor (provides means to specify memory and storage capacity)
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- what else?
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Proposed change
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===============
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Establish an abstract base class to model the desired functionality:
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.. code:: python
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class AmphoraComputeDriver(object):
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def get_logger(self):
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""" return the logger to use - this is a way to inject a
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custom logger for testing, etc
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:returns: the logger
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"""
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raise NotImplementedError
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def build(self, amphora_type = VM, amphora_flavor = None,
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image_id = None, keys = None, sec_groups = None,
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network_ids = None ):
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""" build a new amphora.
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:param amphora_type: The type of amphora to create. For
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version 0.5, only VM is supported. In the future this
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may support Container, BareMetal, and HWLoadBalancer.
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:param amphora_flavor: Optionally specify a flavor. The
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interpretation of this parameter will depend upon the
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amphora type and may not be applicable to all types.
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:param image_id: ID of the base image for a VM amphora
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:param keys: Optionally specify a list of ssh public keys
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:param sec_groups: Optionally specify list of security
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groups
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:param network_ids: A list of network_ids to attach to
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the amphora
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:returns: The id of the new instance.
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"""
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raise NotImplementedError
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def delete(self, amphora_id):
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""" delete the specified amphora
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"""
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raise NotImplementedError
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def status(self, amphora_id):
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""" Check whether the specified amphora is up
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:param amphora_id: the ID of the desired amphora
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:returns: the nova response from the amphora
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"""
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raise NotImplementedError
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def get_amphora(self, amphora_name = None, amphora_id = None):
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""" Try to find a amphora given its name or id
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:param amphora_name: the name of the desired amphora
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:param amphora_id: the id of the desired amphora
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:returns: the amphora object
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"""
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raise NotImplementedError
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def start(self, amphora_id):
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""" start the specified instance
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:param amphora_id: the id of the instance to start
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"""
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raise NotImplementedError
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def suspend(self, amphora_id):
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""" suspend the specified instance
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:param amphora_id: the id of the instance to suspend
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"""
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raise NotImplementedError
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def resume(self, amphora_id):
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""" resume the specified instance
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:param amphora_id: the id of the instance to suspend
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"""
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raise NotImplementedError
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def stop(self, amphora_id):
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""" stop the specified instance
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:param amphora_id: the id of the instance to stop
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"""
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raise NotImplementedError
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def backup(self, amphora_id):
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""" create a backup of the specified instance. The
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format of the backup is implementation-defined
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:param amphora_id: the id of the instance to snapshot
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"""
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raise NotImplementedError
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Exception Model
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---------------
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The driver is expected to raise the following well defined exceptions:
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* NotImplementedError - this functionality is not implemented/not supported
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* AmphoraComputeError - a super class for all other exceptions and the catch
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all if no specific exception can be found
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* AmphoraBuildError - An amphora of the specified type could
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not be built
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* DeleteFailed - this amphora couldn't be deleted
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* InstanceNotFoundError - an instance matching the desired criteria
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could not be found
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* NotSuspendedError - resume() attempted on an instance that was not suspended
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Things a good driver should do:
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-------------------------------
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* Non blocking operations - If an operation will take a long time to execute,
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perform it asynchronously. The definition of "a long time" is open to
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interpretation, but a common UX guideline is 200 ms
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* We might employ a circuit breaker to insulate driver
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problems from controller problems [1]
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* Use appropriate logging
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* Use the preferred threading model
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This will be demonstrated in the Noop-driver code.
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Alternatives
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------------
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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None
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None - since initial version
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Other end user impact
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---------------------
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None
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Performance Impact
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------------------
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Minimal
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Other deployer impact
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---------------------
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Deployers need to make sure to bundle the compatible
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versions of amphora, driver, controller --
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Developer impact
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----------------
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Need to write towards this clean interface.
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Implementation
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==============
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Assignee(s)
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-----------
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Al Miller
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Work Items
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----------
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* Write abstract interface
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* Write Noop driver
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* Write tests
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Dependencies
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============
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None
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Testing
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=======
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* Unit tests with tox and Noop-Driver
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* tempest tests with Noop-Driver
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Documentation Impact
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====================
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None - this is an internal interface and need not be externally
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documented.
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References
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==========
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[1] http://martinfowler.com/bliki/CircuitBreaker.html
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