How to Manage Load Balancers

After you create a load balancer and add Droplets to it, you can manage and modify it on its detail page.

First, click Networking in the main navigation, and then click Load Balancers to go to the load balancer index page. Click on an individual load balancer’s name to go to its detail page, which has three tabs:

  • Droplets, where you can view the Droplets currently attached to the load balancer and modify the backend Droplet pool.

  • Graphs, where you can view graphs of traffic patterns and infrastructure health.

  • Settings, where you can set or customize the forwarding rules, balancing algorithm, sticky sessions, health checks, SSL forwarding, and PROXY protocol.

Manage the Backend Droplet Pool

In the Droplets tab, you can view and modify the load balancer’s backend Droplet pool.

The load balancer detail page on the Droplets tab

This page displays information about the status of each Droplet, its downtime, and other health metrics. Clicking on a Droplet name will take you to the Droplet’s detail page.

If you are managing backend Droplets by name, you can add additional Droplets by clicking the Add Droplets button on this page. If you are managing by tag, you will instead have an Edit Tag button.

View Graphs

Click the Graphs tab to get a visual representation of traffic patterns and infrastructure health.

The load balancer detail page on the Graphs tab

The Frontend section displays graphs related to requests to the load balancer itself:

  • Requests per second
  • Average request duration
  • Connections
  • HTTP responses
  • Traffic received/sent

The Droplets section displays graphs related to the backend Droplet pool:

  • Downtime
  • HTTP responses
  • Queue size
  • Health checks

Modify Advanced Settings

Click the Settings tab to modify the way that the load balancer functions.

The load balancer settings screen

Forwarding Rules

Forward rules define how traffic is routed from the load balancer to its backend Droplets. The left side of each rule defines the listening port and protocol on the load balancer itself, and the right side defines where and how the requests will be routed to the backends.

You can change the protocols using the drop down menus. If you use HTTPS or HTTP2, you will need an an SSL certificate or to use SSL passthrough.

Algorithm

The algorithm a load balancer uses determines how it chooses which backend Droplet to route traffic to. There are two algorithms available:

  • The default round robin algorithm sends requests to each available backend in turn.

  • The alternative least connections algorithm sends requests to the backend with the least number of active connections. This can be a better choice for traffic with longer sesssions.

Sticky Sessions

Sticky sessions make the load balancer always sends requests from the same client to the same backend server by setting a cookie with a configurable name and TTL (to define how long the cookie is valid). This persistence is useful if an application’s sessions rely on connecting to the same backend for each request.

Health Checks

The load balancer will only forward requests to Droplets that pass health checks. You can customize the criteria for the health checks.

In the Target section, you choose the Protocol (HTTP or TCP), Port (80 by default), and Path (/ by default) that Droplets should respond on.

In the Additional Settings section, you choose:

  • The Check Interval, which is how many seconds the load balancer will wait between health checks.
  • The Response Timeout, which is how may seconds the load balancer will wait between responses.
  • The Unhealthy Threshold, which is how many consecutive times a Droplet must fail a health check before the load balancer stops forwarding traffic to it.
  • The Healthy Threshold, which is how many consecutive times a Droplet must pass a health check before the load balancer will forward traffic to it.

SSL

The SSL option redirects HTTP requests on port 80 to HTTPS port 443. When you enable this option, HTTP URLs will be forwarded to HTTPS with a 307 redirect.

Proxy Protocol

By default, client connection information (like the client IP address) only reaches the load balancer. PROXY protocol passes this information along to the backend Droplets.

Backend services need to accept PROXY protocol headers or the Droplets will fail the load balancer’s health checks.