Scaling an Application Using App Autoscaler

This topic describes how Pivotal Cloud Foundry (PCF) users with the Space Developer role can set up and configure the App Autoscaler service to automatically scale apps based on rules that they set.

You can use the App Autoscaler command-line interface (CLI) plugin to configure App Autoscaler rules from the command line.

NOTE: Space Managers, Space Auditors, and all Org roles do not have permission to use App Autoscaler. For help managing user roles, see Managing User Accounts and Permissions Using the Apps Manager.

App Autoscaler Overview

App Autoscaler is a marketplace service that helps control the cost of running apps while maintaining app performance.

To balance app performance and cost, Space Developers can use App Autoscaler to do the following:

  • Configure rules that adjust instance counts based on metrics thresholds such as CPU Usage
  • Modify the maximum and minimum number of instances for an app, either manually or following a schedule

Set Up App Autoscaler

To use App Autoscaler, you must create an instance of the App Autoscaler service and bind it to any app you want to autoscale. You can do this using either the Apps Manager or from the Cloud Foundry Command Line Interface (cf CLI):

Manual Scaling Overrides Autoscaler

If you manually scale an app bound to an App Autoscaler service instance, the App Autoscaler instance automatically unbinds from that app, and the app scales to the manual setting.

Configure Autoscaling for an App

App Autoscaler keeps instance counts within an allowable range defined by minimum and maximum values, or instance limits.

  1. In Apps Manager, select an app from the space in which you created the App Autoscaler service and click Services.

  2. Select the App Autoscaler service from the list of services, and then click Manage.

Follow the procedures in the sections below to set any of the following:

Instance Limits

Follow these steps to manually modify instance limits:

Note: You can also schedule changes to your instance limits for a specific date and time.

  1. Click the edit icon next to Instance Limits.

  2. Enter values for Minimum and Maximum.

  3. Click Save.

    Limits

Scaling Rules

To keep your apps available without wasting resources, App Autoscaler increments or decrements instance counts based on how current metrics compare with configurable High and Low thresholds.

How App Autoscaler Determines When to Scale

App Autoscaler scales apps as follows:

  • Increment by one instance when any metric exceeds the High threshold specified
  • Decrement by one instance only when all metrics fall below the Low threshold specified

Scaling Rule Metrics

The table below lists the metrics that you can base App Autoscaler rules on:

Metric Description
CPU Utilization Average CPU percentage for all instances of the app.
HTTP Throughput Total HTTP Requests per second (divided by total app instances).
HTTP Latency Average Latency of applications response to HTTP requests. This does not include Gorouter processing time or other network latency.
Average is calculated on the middle 99% or middle 95% of all HTTP requests.

Add a Scaling Rule

  1. Click the edit icon next to Scaling Rules. The Edit Scaling Rules pane appears.

  2. Click the + add rule icon.

  3. In the Select a Metric dropdown, select the metric for the new scaling rule to threshold.

  4. Click the slider next to the Select a Metric dropdown to enable the new rule.

    Note: New rules are disabled by default.

  5. Set the Low and High thresholds for the metric using the table above as a guide.

    Scaling Rules

  6. Click Save.

Delete a Scaling Rule

  1. Click the × delete icon next to the Select a Metric dropdown.

  2. Click Save.

Scheduled Limit Changes

Because app demand often follows a weekly, daily, or hourly schedule, you can schedule Autoscaler to change the allowable instance range to track expected surges or quiet periods.

Create or Modify a Scheduled Limit Change

  1. Click the clock icon next to Scheduled Limit Changes.

  2. Click + ADD NEW to add a new scheduled limit change or choose an existing entry to modify by clicking the edit icon next to an existing entry.

    • To delete an existing entry, click the delete icon X next to an existing entry.
  3. Edit the following values:
    Scheduled limit changes

    • Date: Month, Day, Year and Time: Set the date and time of the change.
    • Repeat (optional): Set the day of the week for which you want to repeat the change.
    • Min and Max: Set the allowable range within which App Autoscaler can change the instance count for an app.
  4. Click SAVE.

Example: Scale Down for the Weekend

To schedule an app to scale down for a weekend, you can enter two rules as follows:

  1. Scale down to a single instance on Friday evening:
    • Month, Day, Year and Time: Dec, 2, 2016 and 7:00 PM
    • Repeats: Fr
    • Min and Max: 1 and 1
  2. Increase instances to between 3 and 5 on Monday morning:
    • Month, Day, Year and Time: Dec, 5, 2016 and 7:00 AM
    • Repeats: M
    • Min and Max: 3 and 5

App Autoscaler Events and Notifications

App Autoscaler logs all autoscaling events including scaling decisions and binding auto-disable events.

View Event History

To view all autoscaling events in the past 24 hours, click the view more icon in the Event History section of the App Autoscaler UI.

Scaling Event History

Manage Autoscaler Notifications

Autoscaler emails and/or texts its event notifications to all space users by default.

Follow these steps to subscribe or unsubscribe from autoscaling event notifications:

  1. Navigate to the Manage Notifications page of PCF.

    Note: If installed, Notifications Management should be available at https://notifications-ui.YOUR-SYSTEM-DOMAIN/preferences.

  2. Choose which notifications you want to receive from App Autoscaler:

    Notifications

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