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


              Healtch Check Response Format for HTTP APIs
                   draft-inadarei-api-health-check-00

Abstract

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

Note to Readers

   _RFC EDITOR: please remove this section before publication_

   The issues list for this draft can be found at
   https://github.com/inadarei/rfc-healthcheck/issues [1].

   The most recent draft is at https://inadarei.github.io/rfc-
   healthcheck/ [2].

   Recent changes are listed at https://github.com/inadarei/rfc-
   healthcheck/commits/master [3].

   See also the draft's current status in the IETF datatracker, at
   https://datatracker.ietf.org/doc/draft-inadarei-api-healthcheck/ [4].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 19, 2018.





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Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
   2.  API Health Response . . . . . . . . . . . . . . . . . . . . .   3
   3.  Another subtitle  . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Final subtitle  . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Media Type Registration . . . . . . . . . . . . . . . . .   6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
     7.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   7
   Appendix B.  Creating and Serving Health Responses  . . . . . . .   7
   Appendix C.  Consuming Health Check Responses . . . . . . . . . .   8
   Appendix D.  Frequently Asked Questions . . . . . . . . . . . . .   8
     D.1.  Why not use (insert other health check format)? . . . . .   8
     D.2.  Why doesn't the format allow references or inheritance? .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

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.





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   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:

   o  Flexible deployment - since operational tooling and API clients
      can rely on rich, uniform format, they can be safely combined and
      substituted as needed.

   o  Evolvability - new APIs, conforming to the standard, can safely be
      introduced in any environment and ecosystem that also conforms to
      the same standard, without costly coordination and testing
      requirements.

   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/vnd.health+json".

   *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:

   o  status: (required) indicates whether the service status is
      acceptable or not.  API publishers SHOULD use following values for
      the field:



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      *  "pass": healthy,

      *  "fail": unhealthy, and

      *  "warn": healthy, with some concerns.

      For "pass" and "warn" statuses HTTP response code in the 2xx - 3xx
      range MUST be used. for "fail" status HTTP response code in the
      4xx - 5xx range MUST be used.

      In case of "warn" status, additional information SHOULD be
      provided, utilizing optional fields of the response.

   o  serviceID: (optional) unique identifier of the service, in the
      application scope.

   o  description: (optional) human-friendly description of the service.

   o  memory: (optional) array of sizes for the currently utilized
      resident memory (in kilobytes) on each of the logical nodes
      backing the service.  Logical node can be a physical server, VM, a
      container or any other logical unit that makes sense for service
      publisher.

   o  cpu: (optional) array of cpu utiliation percentage on each of the
      logical nodes backing the service.  Logical node can be a physical
      server, VM, a container or any other logical unit that makes sense
      for service publisher.

   o  uptime: (optional) current uptime in seconds since the last
      restart

   o  notes: (optional) array of notes relevant to current state of
      health

   o  output: (optional) raw error output, in case of "fail" or "warn"
      states.  This field SHOULD be omitted for "pass" state.

   o  details: (optional) an array of objects optionally providing
      additional information regarding the various sub-components of the
      service.

   o  links: (optional) an array of objects containing link relations
      and URIs [RFC3986] for external links that MAY contain more
      information about the health of the endpoint.  Per web-linking
      standards [RFC5988] a link relationship SHOULD either be a common/
      registered one or be indicated as a URI, to avoid name clashes.




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   For example:

     GET /health HTTP/1.1
     Host: example.org
     Accept: application/vnd.health+json

     HTTP/1.1 200 OK
     Content-Type: application/vnd.health+json
     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": "http://api.example.com/about/authz"},
         {
           "rel": "http://api.example.com/rel/thresholds",
           "uri": "http://api.example.com/about/authz/thresholds"
         }
       ]
     }







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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/vnd.health+json 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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [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,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

   [RFC5988]  Nottingham, M., "Web Linking", RFC 5988,
              DOI 10.17487/RFC5988, October 2010,
              <https://www.rfc-editor.org/info/rfc5988>.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <https://www.rfc-editor.org/info/rfc7159>.



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   [RFC7234]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
              RFC 7234, DOI 10.17487/RFC7234, June 2014,
              <https://www.rfc-editor.org/info/rfc7234>.

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,
              <https://www.rfc-editor.org/info/rfc6838>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <https://www.rfc-editor.org/info/rfc7231>.

7.3.  URIs

   [1] https://github.com/inadarei/rfc-healthcheck/issues

   [2] https://inadarei.github.io/rfc-healthcheck/

   [3] https://github.com/inadarei/rfc-healthcheck/commits/master

   [4] https://datatracker.ietf.org/doc/draft-inadarei-api-healthcheck/

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:

   o  A health response endpoint is best located at a memorable and
      commonly-used URI, such as "health" because it will help self-
      discoverability by clients.





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   o  Health check responses can be personalized.  For example, you
      could advertise different URIs, and/or different kinds of link
      relations, to afford different clients access to additional health
      check information.

   o  Health check responses must be assigned a freshness lifetime
      (e.g., "Cache-Control: max-age=3600") so that clients can
      determine how long they could cache them, to avoid overly frequent
      fetching and unintended DDOS-ing of the service.

   o  Custom link relation types, as well as the URIs for variables,
      should lead to documentation for those constructs.

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.





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Author's Address

   Irakli Nadareishvili

   Email: irakli@gmail.com
   URI:   http://www.freshblurbs.com/













































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