Merge "[spec] Consistent resource names"
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doc/specs/in-progress/consistent_resource_names.rst
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doc/specs/in-progress/consistent_resource_names.rst
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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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Consistent Resource Names
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=========================
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To facilitate better cleanup of ephemeral resources created by Rally,
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random resource names need to be consistently used across all
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scenarios and all plugins. Additionally, to support Rally's use
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against systems other than OpenStack, plugins need greater control
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over both the format and the list of characters used in generating
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resource names.
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Problem description
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===================
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Currently we use a few different cleanup mechanisms, some of which
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(Keystone) use resource names, while most others use tenant
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membership. As a result, if Rally is interrupted before cleanup
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completes it may not be possible to know which resources were created
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by Rally (and thus should be cleaned up after the fact).
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Random names are generated from a fairly limited set of digits and
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ASCII letters. This should be configurable by each plugin, along with
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all other parts of the random name, in order to support benchmarking
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systems other than OpenStack, which may have different naming
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restrictions.
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Finally, each Rally task should include some consistent element in its
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resource names, distinct from other Rally tasks, to support multiple
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independent Rally runs and cleanup.
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Proposed change
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===============
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Random names will consist of three components:
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* A random element derived from the task ID that is the same for all
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random names in the task;
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* A random element that should be different for all names in the task;
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and
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* Any amount of formatting as determined by the plugin.
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The format of the random name will be given by a class variable,
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``RESOURCE_NAME_FORMAT``, on each scenario and context plugin. This
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variable is a ``mktemp(1)``-like string that describes the format; the
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default for scenario plugins will be::
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RESOURCE_NAME_FORMAT = "s_rally_XXXXXXXX_XXXXXXXX"
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And for context plugins::
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RESOURCE_NAME_FORMAT = "c_rally_XXXXXXXX_XXXXXXXX"
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The format must have two separate sets of at least three consecutive
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'X's. (That is, they must match:
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``^.*(?<!X)X{3,}(?!X).*(?<!X)X{3,}(?!X)``. This marks a slight
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departure from ``mktemp(1)``, which requires a single set of three or
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more 'X's at the end.) Three 'X's is likely dangerously few --
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offering only 1000 unique names per task -- but necessary in order to
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support systems with eight-character name limits.
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Another variable will control the allowed characters in the random
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portions. The default will be::
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RESOURCE_NAME_ALLOWED_CHARACTERS = \
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"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
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We will attempt to use the task ID, stripped of dashes, for the first
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random portion. If ``RESOURCE_NAME_ALLOWED_CHARACTERS`` does not allow
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all of the characters in the task ID (lowercase letters and digits),
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then we will use a random string generated from the allowed
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characters, with the pRNG seeded with the task ID.
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Alternatives
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------------
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The resources could be recorded as they are created to a database or
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file, and then that information used to perform cleanup later. This is
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insufficient for recovering from a massive Rally failure, though, so
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while it would be simpler in many ways, it does not meet the
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requirements for out-of-band cleanup. It also doesn't support the two
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other goals of this spec -- broader application support and multiple
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concurrent runs -- both of which would still require most of the work
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described herein. It would also not scale well for distributed load
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generation.
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The format and allowed characters could be configured in
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``rally.conf``, but this does not permit a single Rally installation
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to be used for multiple applications with divergent naming
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requirements, and it offloads responsibility for understanding naming
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limitations to the Rally user, not the plugin author.
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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stpierre aka Chris St. Pierre
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Other contributors:
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rvasilets aka Roman Vasilets
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wtakase aka Wataru Takase
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Work Items
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----------
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* Overhaul `rally.common.utils.generate_random_name()` and
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`rally.task.scenarios.base.Scenario._generate_random_name()`. Early
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proof of concept that implements some of the points in this spec:
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https://review.openstack.org/#/c/184888/
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* Find and fix resources that are created without
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generate_random_name().
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Dependencies
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============
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None.
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