rally-openstack/doc/specs/implemented/consistent_resource_names.rst

Consistent Resource Names

To facilitate better cleanup of ephemeral resources created by Rally, random resource names need to be consistently used across all scenarios and all plugins. Additionally, to support Rally's use against systems other than OpenStack, plugins need greater control over both the format and the list of characters used in generating resource names.

Problem description

Currently we use a few different cleanup mechanisms, some of which (Keystone) use resource names, while most others use tenant membership. As a result, if Rally is interrupted before cleanup completes it may not be possible to know which resources were created by Rally (and thus should be cleaned up after the fact).

Random names are generated from a fairly limited set of digits and ASCII letters. This should be configurable by each plugin, along with all other parts of the random name, in order to support benchmarking systems other than OpenStack, which may have different naming restrictions.

Finally, each Rally task should include some consistent element in its resource names, distinct from other Rally tasks, to support multiple independent Rally runs and cleanup.

Proposed change

Random names will consist of three components:

• A random element derived from the task ID that is the same for all random names in the task;
• A random element that should be different for all names in the task; and
• Any amount of formatting as determined by the plugin.

The format of the random name will be given by a class variable, RESOURCE_NAME_FORMAT, on each scenario and context plugin. This variable is a mktemp(1)-like string that describes the format; the default for scenario plugins will be:

RESOURCE_NAME_FORMAT = "s_rally_XXXXXXXX_XXXXXXXX"

And for context plugins:

RESOURCE_NAME_FORMAT = "c_rally_XXXXXXXX_XXXXXXXX"

The format must have two separate sets of at least three consecutive 'X's. (That is, they must match: ^.*(?<!X)X{3,}(?!X).*(?<!X)X{3,}(?!X). This marks a slight departure from mktemp(1), which requires a single set of three or more 'X's at the end.) Three 'X's is likely dangerously few --offering only 1000 unique names per task -- but necessary in order to support systems with eight-character name limits.

Another variable will control the allowed characters in the random portions. The default will be:

RESOURCE_NAME_ALLOWED_CHARACTERS = \
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

We will attempt to use the task ID, stripped of dashes, for the first random portion. If RESOURCE_NAME_ALLOWED_CHARACTERS does not allow all of the characters in the task ID (lowercase letters and digits), then we will use a random string generated from the allowed characters, with the pRNG seeded with the task ID.

Alternatives

The resources could be recorded as they are created to a database or file, and then that information used to perform cleanup later. This is insufficient for recovering from a massive Rally failure, though, so while it would be simpler in many ways, it does not meet the requirements for out-of-band cleanup. It also doesn't support the two other goals of this spec -- broader application support and multiple concurrent runs -- both of which would still require most of the work described herein. It would also not scale well for distributed load generation.

The format and allowed characters could be configured in rally.conf, but this does not permit a single Rally installation to be used for multiple applications with divergent naming requirements, and it offloads responsibility for understanding naming limitations to the Rally user, not the plugin author.

Implementation

Assignee(s)

Primary assignee:

stpierre aka Chris St. Pierre

Other contributors:

rvasilets aka Roman Vasilets wtakase aka Wataru Takase

Work Items

• Overhaul rally.common.utils.generate_random_name() and rally.task.scenarios.base.Scenario._generate_random_name(). Early proof of concept that implements some of the points in this spec: https://review.openstack.org/#/c/184888/
• Find and fix resources that are created without generate_random_name().

Dependencies

None.