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
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and may be updated, replaced, or obsoleted by other documents at any
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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
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document authors. All rights reserved.
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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>.
[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/
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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