rally-openstack/doc/source/plugins/implementation/context_plugin.rst

Context as a plugin

So what are contexts doing? These plugins will be executed before scenario iteration starts. For example, a context plugin could create resources (e.g., download 10 images) that will be used by the scenarios. All created objects must be put into the self.context dict, through which they will be available in the scenarios. Let's create a simple context plugin that adds a flavor to the environment before the benchmark task starts and deletes it after it finishes.

Creation

Inherit a class for your plugin from the base Context class. Then, implement the Context API: the setup() method that creates a flavor and the cleanup() method that deletes it.

from rally.task import context
from rally.common import logging
from rally import consts
from rally import osclients

LOG = logging.getLogger(__name__)


@context.configure(name="create_flavor", order=1000)
class CreateFlavorContext(context.Context):
    """This sample creates a flavor with specified options before task starts
    and deletes it after task completion.

    To create your own context plugin, inherit it from
    rally.task.context.Context
    """

    CONFIG_SCHEMA = {
        "type": "object",
        "$schema": consts.JSON_SCHEMA,
        "additionalProperties": False,
        "properties": {
            "flavor_name": {
                "type": "string",
            },
            "ram": {
                "type": "integer",
                "minimum": 1
            },
            "vcpus": {
                "type": "integer",
                "minimum": 1
            },
            "disk": {
                "type": "integer",
                "minimum": 1
            }
        }
    }

    def setup(self):
        """This method is called before the task starts."""
        try:
            # use rally.osclients to get necessary client instance
            nova = osclients.Clients(self.context["admin"]["credential"]).nova()
            # and than do what you need with this client
            self.context["flavor"] = nova.flavors.create(
                # context settings are stored in self.config
                name=self.config.get("flavor_name", "rally_test_flavor"),
                ram=self.config.get("ram", 1),
                vcpus=self.config.get("vcpus", 1),
                disk=self.config.get("disk", 1)).to_dict()
            LOG.debug("Flavor with id '%s'" % self.context["flavor"]["id"])
        except Exception as e:
            msg = "Can't create flavor: %s" % e.message
            if logging.is_debug():
                LOG.exception(msg)
            else:
                LOG.warning(msg)

    def cleanup(self):
        """This method is called after the task finishes."""
        try:
            nova = osclients.Clients(self.context["admin"]["credential"]).nova()
            nova.flavors.delete(self.context["flavor"]["id"])
            LOG.debug("Flavor '%s' deleted" % self.context["flavor"]["id"])
        except Exception as e:
            msg = "Can't delete flavor: %s" % e.message
            if logging.is_debug():
                LOG.exception(msg)
            else:
                LOG.warning(msg)

Usage

You can refer to your plugin context in the benchmark task configuration files in the same way as any other contexts:

{
    "Dummy.dummy": [
        {
            "args": {
                "sleep": 0.01
            },
            "runner": {
                "type": "constant",
                "times": 5,
                "concurrency": 1
            },
            "context": {
                "users": {
                    "tenants": 1,
                    "users_per_tenant": 1
                },
                 "create_flavor": {
                    "ram": 1024
                }
            }
        }
    ]
}