Just as you would monitor an application to ensure quality performance, so too must you monitor APIs.
APIs serve as vehicles through which apps communicate with each other. More specifically, APIs provide the means through which developers can write HTTP requests and other code to extract information from a web service or application. APIs reduce and often eliminate the need to develop complex integrations that enable customers to use software. Organizations build and expose APIs both for external customers and internal users.
While APIs facilitate vital application communication, they are only valuable if they perform effectively and efficiently. Just as organizations monitor applications, they must monitor APIs, both for performance and functionality.
API performance metrics
Availability and responsiveness are the most important metrics needed to monitor APIs' performance.
If your API is unavailable, customers can't use it. Availability goes beyond uptime, which only tracks when the API is on or off. Use availability metrics that show how long a service is down, how often it goes down and even the reason for the failure. These metrics can also be used to monitor APIs' full, partial or restricted availability.
Even if an API is available, poor responsiveness will severely impact the user experience. Response time measures how long an API takes to react to a call. Latency takes this measurement a step further and tracks the time between when the call was made, the response to the call and when the data sends. These metrics help pinpoint the causes of issues identified by the availability and uptime metrics.
API functional metrics
While it's important to monitor APIs for performance, you should also know who uses an API and how.
API functional metrics show what parts of an API matter most to customers and which ones cause them the most difficulty. The most important functional metrics are traffic source and user type, error data and endpoint valuations.
While many organizations track the number of concurrent API users, the traffic source and user type are more important, as they enable you to delve more deeply into who customers are. Together, these metrics provide valuable insight into how many customers use the API, which parts they use, what is most important to them and why they use the API.
Analyze error information, such as when pages fail to submit and lists of data errors, as you monitor APIs. This kind of tracking reveals code defects and usability issues, which, in turn, provide direction on how to improve an API and streamline how an app processes requests.
Endpoint valuations provide information on how the API processes communications. As the terminal points of a communication channel, APIs send requests to endpoints. For optimal performance, APIs must communicate effectively with their endpoints. Frequency and utilization comparisons show which endpoints are hit most frequently by the API. Through additional analysis, the development team can determine why the API uses those endpoints more than others. When endpoints are attached to multiple services, track service efficiency to see where the team can improve performance by creating more endpoints; alternatively, if there are unused endpoints, a team member can eliminate those that cause bloat -- trimming bloat will reduce ongoing maintenance and cost. Analyze endpoint valuations to gain security vulnerability information, including which endpoints suffered breaches.
Don't stop there
While these metrics help ensure the performance and overall health of an organization's APIs, there are other business-related metrics that are just as critical: cost per project, developer willingness to recommend, data extracts by major competitors and others.
To determine which metrics are most important for your organization, analyze and understand the purpose of each API and the value that the organization expects to gain from it. There are many reasons to develop APIs, and accordingly, there are many potential valuable metrics related to them.