DC/OS Auto-scaling

An autoscaler for mesospheres DC/OS. Works by parsing special marathon application labels which indicate whether the app needs to be auto scaled, the rules that needs to be used for auto scaling, metadata that describes how the application needs to be scaled.

Marathon's v2 api is used to collect data about the running apps. CPU and memory usage are aquired using mesos statistics api where authentication is bypassed given that the slave running this application has access to a mesos dns and can connect to all slaves.

Usage

Run this app in your DC/OS either by directly installing it from the universe or by using this marathon json.

{
  "id": "/dcos-autoscaler",
  "instances": 1,
  "cpus": 0.5,
  "mem": 500,
  "container": {
    "docker": {
      "image": "ahmadposten/dcos-autoscaling"
    }
  }
}

You would need to label your application as autoscalable by adding this label to your application AUTOSCALABLE=true

Specify the minimum and maximum number of instances by AUTOSCALING_MIN_INSTANCES=<minumum number> and AUTOSCALING_MAX_INSTANCES=<maximum number>

Rules are specified by adding labels in the format of

AUTOSCALING_{Rule number}_RULE_{property}

for example If you wish to scale your application up based on cpu utilization you add the following labels to your application

{
  "AUTOSCALABLE": "true",
  "AUTOSCALING_MIN_INSTANCES": "1",
  "AUTOSCALING_MAX_INSTANCES": "10",
  "AUTOSCALING_COOLDOWN_PERIOD": "60",
  "AUTOSCALING_0_RULE_TYPE": "cpu",
  "AUTOSCALING_0_RULE_THRESHOLD": "70",
  "AUTOSCALING_0_RULE_STEP": "2",
  "AUTOSCALING_0_RULE_OPERATOR": "gt",
  "AUTOSCALING_0_RULE_SAMPLES": 5,
  "AUTOSCALING_0_RULE_INTERVAL": 60,
  "AUTOSCALING_0_RULE_ACTION": "increase"
}

By these labels I defined that this application will be scalable, it can never go below 1 instance or above 10 instances. After every scaling activity wait for 1 minute before doing another one if needed. If the cpu utilization exceeds 70 for 5 samples of 1 minutes each increase the instances by 2 instances.

Supported labels

Label	Description	Scope	Possible values
AUTOSCALABLE	Specifies that your application is supervised by the autoscaler	Application	Boolean
AUTOSCALING_MIN_INSTANCES	Specifies the minimum number of instances that your app need to maintain	Application	Integer
AUTOSCALING_MAX_INSTANCES	Specifies the minimum number of instances that your app need to maintain	Application	Integer
AUTOSCALING_COOLDOWN_PERIOD	The number of seconds to wait before going on with another scaling activity	Application	Integer
AUTOSCALING_{X}_RULE_TYPE	The type of the rule x	Rule	cpu, memory
AUTOSCALING_{X}_RULE_THRESHOLD	The threshold of rule x	Rule	Double
AUTOSCALING_{X}_RULE_OPERATOR	The comparison operator (> or <) against the threshold	Rule	gt, lt
AUTOSCALING_{X}_RULE_INTERVAL	The interval every measurement will be taken over in seconds	Rule	Integer
AUTOSCALING_{X}_RULE_SAMPLES	The number of consecutive samples to average and compare to the threshold. Every sample is taken over the specified interval.	Rule	Integer
AUTOSCALING_{X}_RULE_ACTION	The action to take when the rule is triggered.	Rule	increase, decrease
AUTOSCALING_{X}_RULE_STEP	The step to scale by when rule is triggered.	Rule	Integer

Features

• Scale an application up and down based on:
  • CPU
  • Memory
• Configurable number of samples
• Configurable interval
• Configurable Operators (gt, lt)
• Configurable cooldown period (the number of seconds to wait before scaling again)
• Configurable min and max number of instances
• Supports multiple rules

TODO

The project is still not stable and lot's of stuff can be done to improve it and make it production ready. Here are some of the things I was thinking about

• Support scaling based on number of requests
• Support scaling based on network in/out
• Support notifications

and most importantly testing.

Contributing

Everyones contribution is very welcomed. You can pick one item from the TODO list and work on it or you can create an issue if you found a bug or propose an improvement to be made. To actively contribute code to this project:

1. Fork the repo
2. Do you work and make it ready on your fork
3. Submit a pull request

Since this is a new project and it is not actively used (or contributed to except by me) expect responses to your pull requests to be really quick.

License

This source code is distributed under the BSD-3-Clause. Read the License File