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202 lines
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..
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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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Housekeeping Manager Specification
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==========================================
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https://blueprints.launchpad.net/octavia/+spec/housekeeping-manager
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Problem description
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===================
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The Housekeeping Manager will manage the spare amphora pool and the
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teardown of amphorae that are no longer needed. On a configurable
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interval the Housekeeping Manager will check the Octavia database to
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identify the required cleanup and maintenance actions required. The
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amphora-lifecycle-management specification details the Create and
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Deactivate amphora sequences the Housekeeping Manager will follow.
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Proposed change
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===============
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The housekeeping manager will run as a daemon process which will
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perform the following actions:
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* Read the following from the configuration file
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* housekeeping_interval: The time (in seconds) that the
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housekeeping manager will sleep before running its checks
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again.
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* spare_amphora_pool_size: The desired number of spare amphorae.
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* maximum_deploying_amphora_count: The maximum number of amphorae
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that may be deployed simultaneously.
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* maximum_preserved_amphora_count: How many deactivated amphorae to
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preserve. 0 means delete, 1 or greater means keep up to that many
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amphorae for future diagnostics. Only amphorae in the ERROR and
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PRESERVE states are eligible to be preserved. TODO: Right now
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there is no PRESERVE state, for this to work we would need to
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define one in the amphora spec.
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* preservation_scheme
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* "keep": keep all preserved amphorae
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* "cycle": maintain a queue of preserved amphorae, deleting the
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oldest one when a new amphora is preserved.
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* preservation_method: Preservation must take into account the
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possibility that amphorae instantiated in the future may reuse MAC
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addresses.
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* "unplug": Disconnect the virtual NICs from the amphora
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* "snapshot": Take a snapshot of the amphora, then stop it
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* Get the spare pool size
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* Log the spare pool size
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* If the spare pool size is less than the spare pool target
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capacity, initiate creation of appropriate number of amphorae.
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* Obtain the list of deactivated amphorae and schedule their removal.
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If preservation_count > 0, and there are fewer than that many
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amphorae in the preserved pool, preserve the amphora. After the
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preserved pool size reaches preservation_count, use
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preservation_scheme to determine whether to keep newly failed
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amphorae.
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* Sleep for the time specified by housekeeping_interval.
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* Return to the top
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Establish a base class to model the desired functionality:
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.. code:: python
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class HousekeepingManager(object):
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""" Class to manage the spare amphora pool. This class should do
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very little actual work, its main job is to monitor the spare pool
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and schedule creation of new amphrae and removal of used amphrae.
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By default, used amphorae will be deleted, but they may optionally
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be preserved for future analysis.
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"""
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def get_spare_amphora_size(self):
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""" Return the target capacity of the spare pool """
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raise NotImplementedError
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def get_ready_spare_amphora_count(self):
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""" Return the number of available amphorae in the spare pool
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"""
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raise NotImplementedError
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def create_amphora(self, num_to_create = 1):
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""" Schedule the creation of the specified number of amphorae
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to be added to the spare pool."""
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raise NotImplementedError
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def remove_amphora(self, amphora_ids):
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""" Schedule the removal of the amphorae specified by
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amphora_ids."""
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raise NotImplementedError
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Exception Model
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---------------
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The manager is expected to raise or pass along the following
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well-defined exceptions:
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* NotImplementedError - this functionality is not implemented/not supported
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* AmphoraDriverError - 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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* NotFoundError - this amphora couldn't be found/ was deleted by nova
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* UnauthorizedException - the driver can't access the amphora
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* UnavailableException - the amphora is temporary unavailable
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* DeleteFailed - this load balancer couldn't be deleted
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Alternatives
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------------
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Data model impact
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-----------------
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Requires the addition of the housekeeping_interval, spare_pool_size,
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spare_amphora_pool_size, maximum_preserved_amphora_count,
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preservation_scheme, and preservation_method to the config.
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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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Must follow standard practices for database access.
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Notifications impact
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--------------------
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Other deployer impact
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---------------------
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Other end user impact
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---------------------
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There should be no end-user-visible impact.
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Performance Impact
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------------------
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The housekeeping_interval and spare_pool_size parameters will be
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adjustable by the operator in order to balance resource usage against
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performance.
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Developer impact
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----------------
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Developers of other modules need to be aware that amphorae may be
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created, deleted, or saved for diagnosis by this daemon.
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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 <ajmiller>
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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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Amphora driver
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Config manager
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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 - we won't document the interface for 0.5. If that changes
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we need to write an interface documentation so
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3rd party drivers know what we expect.
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References
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==========
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