A guide to API health check

APIs are everywhere, powering the functionality of a wide range of applications. As a result, they're hot, and with good reason. Having a well-developed API can make it easy for third-party developers to integrate into your product, which can help drive growth and even create a whole new revenue stream. **But to reap all that goodness, you need to monitor your API health and performance.**

Table of Contents

---

• What is an API health check
• API health check list
• API health check vs. API ping
• API health check best practices
  • Automate API health checks
  • Check API health as frequently as possible
  • Disable Cache
  • Response Time Matters
  • JSON Response
  • Response Status Code
  • Consider protecting your health check endpoint
• Usecases for API health check endpoints
• API health check endpoint types
• API health check with Testfully
• FAQ
  • What is API health check?
  • What is the API ping endpoint?
  • What is the difference between API health check and API Ping?

---

What is an API health check

At its core, the API health check is an API monitoring method that checks your API and alerts you when it notices something’s amiss. Consider it a diagnostic tool for your codebase that can help you find problems before they become more significant headaches than they need to be.

API health check endpoint returns the operational status of the API

API health check list

There is a broad range of items that an API health check endpoint can check; which one should be included and which one should be missed? As a rule of thumb, the API health check endpoint must check anything that may interrupt the API from serving incoming requests. This is different for each API, but we have listed some of the most items to include in your API health check endpoint:

Check	Description
Downstream Operation Status	Your API may depend on other APIs to operate. Make sure to check the operational status of the downstream APIs you depend on
Database connection	Your API may have an open connection to a data source. Make sure the connection is available at the time of the health check
Database response time	Measure the average response time to a typical DB query
Memory consumption	Spike in memory usage can be because of memory leaks and can interrupt the service
In-flight messages	Does your API works with message queues? Too many in-flight messages can be a sign of an underlying issue

API health check vs. API ping

API ping endpoint responds to requests with a basic 200 OK message. The purpose of the API ping endpoint is to verify that HTTP requests reach the API. In addition, Dev-ops engineers ping APIs (using ping endpoint) to ensure that the API gateway, SSL, routing, and other network-level components work together to deliver a request to the API process.

API ping endpoint barely checks that the API is running and is accessible

As discussed earlier, the API health check endpoint verifies multiple items and responds with the status of the API and its dependencies.

Throughout my career, I have come across many API ping endpoints that return 200 OK while something is wrong with the API. API health check endpoint is superior to the API ping endpoint, covers all use cases of API ping, and offers many more benefits.

We highly recommend our customers develop API health check endpoints and use them for API monitoring.

API health check best practices

It’s essential to monitor your API health every minute and set up alerts if API is not working correctly. Here are some best practices to help you monitor your API health.

Automate API health checks

---

You should automate your entire API health checks via a fault-tolerant API monitoring system. In addition to that, you should avoid rolling out your bespoke API monitoring solution for API health checks. Using a dedicated API monitoring solution minimize the risk associated with monitoring tool downtime and bug. Make sure to check our best API monitoring tools article for a list of available services for API monitoring.

Check API health as frequently as possible

---

Ideally, your API health monitoring tool must check the health of your API every minute. Is it too much? No! Imagine if an API health check happens every hour. What would happen if your API goes down immediately after the last health check? It takes 60 minutes for you to realize your API is down.

Disable Cache

---

Your API process must serve every request to your Restful or GraphQL (micro)service API health check endpoint. By disabling caching on your health endpoint, you prevent HTTP caching from serving the request. As a result, every request to the API health check endpoint returns the most up-to-date status of your microservice.

To disable the cache, add the Cache-Control: no-cache to your endpoint.

Response Time Matters

---

Not only it matters that the API health check endpoint responds, but also it matters how long it took for the endpoint to respond to the request. For example, if the endpoint responds in 30 seconds, there is something wrong with the API.

At Testfully, our customers can set the expected response time for API testing and monitoring. Should it take longer for your API to respond, Testfully starts alerting you.

JSON Response

---

Returning the response of health check in JSON format allows further validation using API monitoring tools.

Response Status Code

---

Leverage the response status code and communicate well with the monitoring tool about the result of a health check. A successful health check should return 200 OK. Use other standard HTTP status codes, including 500 Internal Error, to signal a failure.

The Response Status Code should reflect the overall status of your API.

Consider protecting your health check endpoint

---

Most ping endpoints are publicly available because they don’t provide much internal or sensitive information. On the other hand, API health check endpoints expose information about your service, so it’s a good idea to protect this endpoint. You only need to make sure that your API monitoring tool supports sending API access keys.

Usecases for API health check endpoints

Keeping the API health check endpoints generic allows us to use them for multiple purposes. In this section, we will review some of the everyday use cases of an API health check endpoint

• Container orchestrators and API load balancers can use API health check endpoint to find out about the process status
• Usage of memory, disk, and other server resources can be monitored via API health check endpoints
• Health checks can test APIs dependencies, such as databases and external service endpoints, to confirm availability and normal functioning.

API health check endpoint types

There are at least three different types of API health check endpoints designed to serve specific purposes.

• The readiness endpoint, often available via /health/ready, returns the readiness state to accept incoming requests from the gateway or the upstream proxy. Readiness signals that the app is running normally but isn’t ready to receive requests just yet.

• The liveness endpoint, often available via /health/live, returns the liveness of a microservice. If the check does not return the expected response, it means that the process is unhealthy or dead and should be replaced as soon as possible.

• The generic health check endpoint, often available via /health, returns the status of the service and the dependencies.

Consider the following example: an API that loads JSON-based data into memory to serve requests.

• The /health/ready continues to respond with NOT_READY signal while the API is loading the JSON file since the API cannot serve any request without the file in memory. Therefore, it may take some time for the API to process the entire file.

• The /health/live immediately signals LIVE, even though the app is not ready, to prevent the container orchestrator layer from restarting the app.

API health check with Testfully

In our API Health Monitoring with Testfully article, we explain how you can run a health check for your API in three simple steps. If you prefer to watch a demo, we have recorded a quick demo of our platform for API monitoring.

FAQ

What is API health check?

---

It is a Rest(ful) API endpoint that checks the API itself and all critical dependencies. API health check endpoint returns the check result as the response. Software, QA, and Dev-ops teams use this endpoint to monitor the health of an API using a monitoring tool like Testfully.

What is the API ping endpoint?

---

It is a Rest(ful) API endpoint that responds with 200 OK message. It barely tells the monitoring service that the API process is running and has received the request.

What is the difference between API health check and API Ping?

---

A successful API ping response suggests that the API is running and receives the HTTP requests. A successful API health check response indicates that the API is running and all of the critical parts of the API are working fine.