Welcome to RAX-AutoScaler’s documentation!

RAX-AutoScaler use the rackspace APIs to allow for scaling based on aggregate metrics across a cluster. Can be used and installed on the auto-scale group members or on a dedicated management instance.

Contents:

Quick Start

Installation

pip install RAX-AutoScaler

Configuration

Edit config.json adding the following: - API username - API key - Region name - Autoscaling group section should contain:

  • AutoScale Group UUID
  • Scale Up Policy UUID
  • Scale Down Policy UUID
  • Check Type (agent.cpu, agent.load_average...)
  • Metric Name (depends on the check type)
  • Scale Up Threshold
  • Scale Down Threshold
  • Webhooks Url (Pre & Post commit url(s) for scale up/down)

Usage

Once configured you can invoke the autoscaler.py script.

–cluster option should be used when this script actually runs on auto-scale group members. Otherwise if it is running on a dedicated management instance you do not require this option.

–as-group option should be used when you have multiple groups listed in the config.json file.

–config-file option should be used if config.json file does not exists in current directory or in ‘/etc/rax-autoscaler’ path.

Once tested you should configure this script to run as a cron job either on a management instance or on all cluster members

Cloud Init

You can use the cloud-config file to auto-install RAX-Autoscaler on new servers. For example to do so on Rackspace cloud using supernova

supernova <region> boot –user-data ./cloud-config –image <image id/name> –flavor <flavor id/name> –config-drive=true <server name>

To use this with autoscale you would want to set the userdata of your launch configuration to the base64 encoded string of the file:

"launchConfiguration": {
      "args": {
          "server": {
              "config_drive" : true,
              "flavorRef": "general1-1",
              "imageRef": "CentOS 6.5 (PVHVM)",
              "key_name" : "MY_SSH_KEY",
              "user_data" : "I2Nsb3VkLWNvbmZpZwoKcGFja2FnZXM6CiAgLSBweXRob24tcGlwCgpydW5jbWQ6CiAgLSBbIHBpcCwgaW5zdGFsbCwgUkFYLUF1dG9TY2FsZXIgXQo=",
              "name": "test-autoscale"
          }
      },
      "type": "launch_server"
  }

This has been tested on these images:

  • Ubuntu 14.04 LTS (PVHVM)
  • CentOS 6.5 (PVHVM)

In the example the value of user_data contains the base64 encoded version of the following script:

echo -n "I2Nsb3VkLWNvbmZpZwoKcGFja2FnZXM6CiAgLSBweXRob24tcGlwCgpydW5jbWQ6CiAgLSBbIHBpcCwgaW5zdGFsbCwgUkFYLUF1dG9TY2FsZXIgXQo=" | base64 -D

To base64 encode a script

cat /path/to/USER_DATA | base64

Size of USER_DATA can be reduced with gzip:

cat /path/to/USER_DATA | gzip | base64

Note

RAX-AutoScaler depends on Rackspace Monitoring Agent to get the data from nodes in scaling group.

If the agent is not installed please read: Install the Cloud Monitoring Agent: http://www.rackspace.com/knowledge_center/article/install-the-cloud-monitoring-agent

Contributing

  • Fork it
  • Create your feature branch (git checkout -b my-new-feature)
  • Commit your changes (git commit -am ‘Add some feature’)
  • Push to the branch (git push origin my-new-feature)
  • Create new Pull Request

What is Sphinx?

Sphinx is a tool that helps to generate python documentation. Features:

  • Output formats: HTML (including Windows HTML Help), LaTeX (for printable PDF versions), ePub, Texinfo, manual pages, plain text
  • Extensive cross-references: semantic markup and automatic links for functions, classes, citations, glossary terms and similar pieces of information
  • Hierarchical structure: easy definition of a document tree, with automatic links to siblings, parents and children
  • Automatic indices: general index as well as a language-specific module indices
  • Code handling: automatic highlighting using the Pygments highlighter

Quick start

You can add inline comments about a function or class at the begining for example:

def exit_with_error(msg):
    """This function prints error message and exit with error.

    :param msg: error message
    :type name: str
    :returns: 1 (int) -- the return code

    """

Execute make command with in project directory with doc arg:

make doc

After successful execution updated .html file sould be available here ‘docs/_build/html/’

Indices and tables

License

Copyright 2014 Rackspace US, Inc.

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.