How do you define SLOs?
With applications continually increasing in both scale and complexity, defining SLOs to maintain service quality and up-time has become critical. But with an overwhelming volume and variety of constantly shifting data, where do organizations start to determine their service-level objectives?
“To establish the most meaningful objectives for your organization, the user must be the focus,” Heider said. “Organizations need to view the services their software provides in terms of what is important to the customer or end-user.” Equally important is how user perception of your app aligns with your organization’s strategic and business goals, such as growing a userbase, building market share, or driving sales.
To find your objectives, Renders and Heider noted the importance of identifying key aspects of your business goals. The top 5 service-level objectives they see in the field are useful examples when setting up your own set of objectives.
Top 5 customer SLOs
Application satisfaction. Are your users happy with the application? The industry standard for measuring user experience is called the application performance index (apdex), which provides a quick index between 0 and 1.0 and establishes a baseline depiction of user satisfaction. This metric is a standardized index derived from various application endpoint metrics such as response time, failures, and a variety of other internal data points.
API endpoint success rate. For a given API your application exposes, how reliable is this endpoint? This allows quick insight into the rate of successful calls. This metric tells you what percentage of all the actions a user tried to take resulted in errors. If you run an e-commerce website and 10% of the users are unable to submit payment, this metric can be used to proactively alert you to an area that requires repair or refinement.
Key user action performances. Using a hypothetical e-commerce application as an example; key user action performances could mean the number of checkouts that occur or the number of times a user adds an item to their cart. Anything a user does when navigating through your app or website can be turned into an action-based objective, captured with the right tools, and tracked.
Endpoint synthetic availability. With synthetic availability, you can execute a variety of automated, synthetic tests against your application instead of using real user traffic and build objectives around the results. Synthetically created metrics serve a different purpose than those based on real users. While real user metrics serve as a customer’s point of view on availability, the goal to measure uptime defined in contracts might be based on synthetic periodic checks of services. You can also run synthetic tests in pre-production environments to simulate how users interact with the application.
Number of instances to serve load. How many compute instances is your application using? If you have very little load on the system or a low number of users, but a very high number of computers, CPU, or memory being utilized, this could indicate an application issue, such as processing power wasted on useless tasks. It could also indicate an infrastructure issue like a poorly tuned set of rules that determine how your application should scale. In either instance, more compute often translates to more money spent on running infrastructure. “We can control and monitor this . . . as it can be a sign of architectural cost or inefficiencies,” Renders noted.
