[doc] Add documentation for hook and trigger plugins
update and fix json errors in hook_plugins.rst Change-Id: I8b9d7b40048fdcae2d997a0a757f226d3487d297
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Anton Studenov
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doc/source/plugins/implementation/hook_and_trigger_plugins.rst
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doc/source/plugins/implementation/hook_and_trigger_plugins.rst
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..
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Copyright 2016 Mirantis Inc. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License"); you may
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not use this file except in compliance with the License. You may obtain
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a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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License for the specific language governing permissions and limitations
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under the License.
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.. _hook_and_trigger_plugins:
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Hooks. Hook trigger plugins
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===========================
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Why Hooks?
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----------
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All Rally workloads repeat their actions as many times as it is configured by
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runner. Once run, there is no way to interupt the runner to evaluate any change
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or restart event on the stability of the cloud under test.
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For example we would like to test how configuration change or cloud component
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restart would affect performance and stability.
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Task hooks were added to fill this gap and allow to use Rally for reliability
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and high availability testing. Generally, hooks allow to perform any
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actions on specified iteration or specified time since the workload has been
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started.
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Also, task html-report provides results of hook execution. They can contain
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graphical or textual information with timing and statistics.
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Hooks & Triggers Overview
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-------------------------
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Architecture
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^^^^^^^^^^^^
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Rally uses runners to specify how many times the workload should be executed.
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Hooks do not use runners, instead they rely on trigger plugins to specify when
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and how many times hook should be called. Therefore hooks are isolated from
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workload runners and do not affect them because each hook is executed in
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separate thread.
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Sample of usage
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^^^^^^^^^^^^^^^
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Hooks can be added to the task configuration. Lets take a look at hook
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configuration:
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.. code-block:: json
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{
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"name": "sys_call",
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"args": "/bin/echo 123",
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"trigger": {
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"name": "event",
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"args": {
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"unit": "iteration",
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"at": [5, 50, 200, 1000]
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}
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}
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}
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It specifies hook plugin with name "sys_call". "args" field contains string
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that will be used by sys_call plugin, but in case of any other hook plugin it
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can contain any other Python object, that is assumed to be passed to the hook.
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"trigger" field specifies which trigger plugin should be used to run this hook.
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"trigger" contains similar fields "name" and "args" which represent trigger
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plugin name and arguments for trigger plugin. In this example "event" trigger
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is specified and configured to run the hook at 5th, 50th, 200th and 1000th
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iterations.
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Here is a full task config that contains previous hook configuraiton:
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.. code-block:: json
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{
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"Dummy.dummy": [
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{
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"args": {
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"sleep": 0.01
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},
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"runner": {
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"type": "constant",
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"times": 1500,
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"concurrency": 1
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},
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"hooks": [
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{
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"name": "sys_call",
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"args": "/bin/echo 123",
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"trigger": {
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"name": "event",
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"args": {
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"unit": "iteration",
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"at": [5, 50, 200, 1000]
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}
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}
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}
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]
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}
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]
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}
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.. note::
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In this example, runner is configured to run workload 1500 times. So there
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is a limit for iterations and hook will be triggered only if certain
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iteration is started by runner. In other words, if trigger specifies
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iteration out of runner iterations scope then such trigger will not be
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called.
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Task report for this example will contain minimal information about hook
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execution: duration of each hook call and its status(success of failure).
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Let's take a look at more complicated config that can produce graphical
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and textual information.
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.. code-block:: yaml
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---
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Dummy.dummy:
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-
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args:
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sleep: 0.75
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runner:
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type: "constant"
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times: 20
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concurrency: 2
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hooks:
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- name: sys_call
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description: Run script
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args: sh rally/rally-jobs/extra/hook_example_script.sh
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trigger:
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name: event
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args:
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unit: iteration
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at: [2, 5, 8, 13, 17]
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- name: sys_call
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description: Show time
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args: date +%Y-%m-%dT%H:%M:%S
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trigger:
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name: event
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args:
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unit: time
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at: [0, 2, 5, 6, 9]
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- name: sys_call
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description: Show system name
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args: uname -a
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trigger:
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name: event
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args:
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unit: iteration
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at: [2, 3, 4, 5, 6, 8, 10, 12, 13, 15, 17, 18]
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sla:
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failure_rate:
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max: 0
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hook_example_script.sh generates dummy output in JSON format. Grafical
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information format is the same as for workloads and the same types of
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charts are supported for the hooks.
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Here is a report that shows aggregated table and chart with hook results:
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.. image:: ../../images/Hook-Aggregated-Report.png
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Here is report that shows lines chart and pie chart for first hook on
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the second iteration:
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.. image:: ../../images/Hook-Per-Hook-Report.png
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Browse existing Hooks_ and Triggers_.
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Writing your own Hook plugin
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----------------------------
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Problem description
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^^^^^^^^^^^^^^^^^^^
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Hook plugin should implement custom action that can be done one or multiple
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times during the workload. Examples of such actions might be the following:
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- Destructive action inside cloud (`Fault Injection`_)
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- Getting information about current state of cloud (load/health)
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- Upgrading/downgrading a component of cloud
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- Changing configuration of cloud
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- etc.
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Plugin code
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^^^^^^^^^^^
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The following example shows simple hook code that performs system call.
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It is inherited from the base *Hook* class and contains implemented ``run()``
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method:
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.. code-block:: python
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import shlex
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import subprocess
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from rally import consts
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from rally.task import hook
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@hook.configure(name="simple_sys_call")
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class SimpleSysCallHook(hook.Hook):
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"""Performs system call."""
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CONFIG_SCHEMA = {
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"$schema": consts.JSON_SCHEMA,
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"type": "string",
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}
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def run(self):
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proc = subprocess.Popen(shlex.split(self.config),
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stdout=subprocess.PIPE,
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stderr=subprocess.STDOUT)
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proc.wait()
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if proc.returncode:
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self.set_error(
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exception_name="n/a", # no exception class
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description="Subprocess returned {}".format(proc.returncode),
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details=proc.stdout.read(),
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)
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Any exceptions risen during execution of ``run`` method will be caught by Hook
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base class and saved as a result. Although hook should manually call
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``Hook.set_error()`` to indicate logical error in case if there is no exception
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raised.
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Also there is a method for saving charts data: ``Hook.add_output()``.
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Plugin Placement
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^^^^^^^^^^^^^^^^
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There are two folders for hook plugins:
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- `OpenStack Hooks`_
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- `Common Hooks`_
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Sample of task that uses Hook
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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.. code-block:: json
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{
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"Dummy.dummy": [
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{
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"args": {
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"sleep": 0.01
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},
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"runner": {
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"type": "constant",
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"times": 10,
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"concurrency": 1
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},
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"hooks": [
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{
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"name": "simple_sys_call",
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"args": "/bin/echo 123",
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"trigger": {
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"name": "event",
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"args": {
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"unit": "iteration",
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"at": [3, 6]
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}
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}
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}
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]
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}
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]
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}
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Results of task execution
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^^^^^^^^^^^^^^^^^^^^^^^^^
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Result of previous task example:
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.. image:: ../../images/Hook-Results.png
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Writing your own Trigger plugin
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-------------------------------
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Problem description
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^^^^^^^^^^^^^^^^^^^
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Trigger plugin should implement an event processor that decides whether to
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start hook or not. Rally has two basic triggers that should cover most cases:
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- `Event Trigger`_
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- `Periodic Trigger`_
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Plugin code
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^^^^^^^^^^^
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This example shows the code of the existing Event trigger:
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.. code-block:: python
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from rally import consts
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from rally.task import trigger
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@trigger.configure(name="event")
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class EventTrigger(trigger.Trigger):
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"""Triggers hook on specified event and list of values."""
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CONFIG_SCHEMA = {
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"type": "object",
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"$schema": consts.JSON_SCHEMA,
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"oneOf": [
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{
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"properties": {
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"unit": {"enum": ["time"]},
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"at": {
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"type": "array",
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"minItems": 1,
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"uniqueItems": True,
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"items": {
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"type": "integer",
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"minimum": 0,
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}
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},
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},
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"required": ["unit", "at"],
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"additionalProperties": False,
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},
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{
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"properties": {
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"unit": {"enum": ["iteration"]},
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"at": {
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"type": "array",
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"minItems": 1,
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"uniqueItems": True,
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"items": {
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"type": "integer",
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"minimum": 1,
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}
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},
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},
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"required": ["unit", "at"],
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"additionalProperties": False,
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},
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]
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}
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def get_listening_event(self):
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return self.config["unit"]
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def on_event(self, event_type, value=None):
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if not (event_type == self.get_listening_event()
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and value in self.config["at"]):
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# do nothing
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return
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super(EventTrigger, self).on_event(event_type, value)
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Trigger plugins must override two methods:
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- ``get_listening_event`` - this method should return currently configured
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event name. (So far Rally supports only "time" and "iteration")
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- ``on_event`` - this method is called each time certain events occur.
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It calls base method when the hook is triggered on specified event.
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Plugin Placement
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^^^^^^^^^^^^^^^^
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All trigger plugins should be placed in `Trigger folder`_.
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.. references:
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.. _Hooks: ../plugin_reference.html#task-hooks
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.. _Triggers: ../plugin_reference.html#task-hook-triggers
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.. _Fault Injection: ../plugin_reference.html#fault-injection-hook
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.. _Event Trigger: ../plugin_reference.html#event-hook-trigger
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.. _Periodic Trigger: ../plugin_reference.html#periodic-hook-trigger
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.. _Common Hooks: https://github.com/openstack/rally/tree/master/rally/plugins/common/hook
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.. _OpenStack Hooks: https://github.com/openstack/rally/tree/master/rally/plugins/openstack/hook
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.. _Trigger folder: https://github.com/openstack/rally/tree/master/rally/plugins/common/trigger
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@ -41,7 +41,7 @@ of hook plugins that should be executed on this iteration.
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"args": {
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"cmd": "bash enable_factor_1"
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},
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"trigger: {
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"trigger": {
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"name": "event",
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"args": {
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"unit": "time",
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@ -54,7 +54,7 @@ of hook plugins that should be executed on this iteration.
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"args": {
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"cmd": "bash enable_factor_2"
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},
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"trigger: {
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"trigger": {
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"name": "event",
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"args": {
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"unit": "iteration",
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@ -67,7 +67,7 @@ of hook plugins that should be executed on this iteration.
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"args": {
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"cmd": "bash enable_factor_3"
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},
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"trigger: {
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"trigger": {
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"name": "periodic",
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"args": {
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"unit": "iteration",
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@ -82,7 +82,7 @@ of hook plugins that should be executed on this iteration.
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"args": {
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"cmd": "bash enable_factor_4"
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},
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"trigger: {
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"trigger": {
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"name": "periodic",
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"args": {
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"unit": "time",
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