Network Working Group I. Nadareishvili
Internet-Draft January 15, 2018
Intended status: Informational
Expires: July 19, 2018

Healtch Check Response Format for HTTP APIs


This document proposes a “health check response” format for API HTTP clients.

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Table of Contents

1. Introduction

Vast majority of modern APIs, that drive data to web and mobile applications use HTTP [RFC7230] as a transport protocol. The health and uptime of these APIs determine availability of the applications themselves. In distributed systems built with a number of APIs, understanding the health status of the APIs and making corresponding decisions, for failover or circuit-breaking, are essential for providing highly available solutions.

There exists a wide variety of operational software that relies on the ability to read health check response of APIs. There is currently no standard for the health check output response, however, so most applications either rely on the basic level of information included in HTTP status codes [RFC7231] or use task-specific formats.

Usage of task-specific or application-specific rformats creates significant challenges, disallowing any meaningful interoprerability across different implementations and between different tooling.

Standardizing a format for health checks can provide any of a number of benefits, including:

This document defines a “health check” format using the JSON format [RFC7159] for APIs to use as a standard point for the health information they offer. Having a well-defined format for this purpose promotes good practice and tooling.

1.1. Notational Conventions

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [RFC2119].

2. API Health Response

An API Health Response Format (or, interchangeably, “health check response”) uses the format described in [RFC7159] and has the media type “application/”.

Note: this media type is not final, and will change before final publication.

Its content consists of a single mandatory root field and several optional fields:

For example:

  GET /health HTTP/1.1
  Accept: application/

  HTTP/1.1 200 OK
  Content-Type: application/
  Cache-Control: max-age=3600
  Connection: close

    "serviceID": "service:authz",
    "description": "health of authz service",
    "status": "pass",
    "memory": [4096, 1024, 3456],
    "cpu": [20, 40, 50],
    "uptime": "1209600",
    "notes": [""],
    "output": "",
    "details": [
        "id": "dfd6cf2b-1b6e-4412-a0b8-f6f7797a60d2",
        "name": "sub-component-X",
        "status": "pass",
        "value": "12313",
        "output": ""
        "id": "3c1f048c-a4be-4aa2-83e6-2629073d19dc",
        "name": "sub-component-Y",
        "status": "warn",
        "value": "0920394",
        "output": "Close to capacity"
    "links": [
      {"rel": "about", "uri": ""},
        "rel": "",
        "uri": ""

3. Another subtitle

Lorem Ipsum

4. Final subtitle

Lorem ipsum

5. Security Considerations

Clients need to exercise care when reporting health information. Malicious actors could use this information for orchestrating attacks. In some cases the health check endpoints may need to be authenticated and institute role-based access control.

6. IANA Considerations

6.1. Media Type Registration

TODO: application/ will be submitted for registration per [RFC6838]

7. References

7.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC3986] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 5226, DOI 10.17487/RFC5226, May 2008.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, DOI 10.17487/RFC5988, October 2010.
[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 2014.
[RFC7234] Fielding, R., Nottingham, M. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Caching", RFC 7234, DOI 10.17487/RFC7234, June 2014.

7.2. Informative References

[RFC6838] Freed, N., Klensin, J. and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013.
[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014.
[RFC7231] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014.

Appendix A. Acknowledgements

Thanks to Mike Amundsen, Erik Wilde, Justin Bachorik and Randall Randall for their suggestions and feedback. And to Mark Nottingham for blueprint for authoring RFCs easily.

Appendix B. Creating and Serving Health Responses

When making an health check endpoint available, there are a few things to keep in mind:

Appendix C. Consuming Health Check Responses

Clients might use health check responses in a variety of ways.

Note that the health check response is a “living” document; links from the health check response MUST NOT be assumed to be valid beyond the freshness lifetime of the health check response, as per HTTP’s caching model [RFC7234].

As a result, clients ought to cache the health check response (as per [RFC7234]), to avoid fetching it before every interaction (which would otherwise be required).

Likewise, a client encountering a 404 (Not Found) on a link is encouraged obtain a fresh copy of the health check response, to assure that it is up-to-date.

Appendix D. Frequently Asked Questions

D.1. Why not use (insert other health check format)?

There are a fair number of existing health check formats. However, these formats have generally been optimised for particular use-cases, and less capable of fitting into general scenarios, optimized for interoperability.

D.2. Why doesn’t the format allow references or inheritance?

Implementing them would add considerable complexity and the associated potential for errors (both in the specification and by its users). For the sake of interoperability and ease of implementation this specification doesn’t attempt to create the most powerful format possible.

Author's Address

Irakli Nadareishvili EMail: URI: