HTTP Gateway Description Format

1.1. Notational Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

3.1. Site

The "site" descriptor is a JSON object containing information about the HTTP server that the gateway exposes on behalf of the origin. It is a JSON object that contains zero or more of the following members:¶

• "exposed-origins": an array of strings containing Unicode serializations of origins (Section 6.1 of [RFC6454]) that are exposed by the gateway¶
• "backend-origins": an array of strings containing Unicode serializations of origins that the gateway uses as origin server(s) for the exposed origin(s)¶

For example:¶

{
  "description": "The Example CDN configuration for example.com",
  "generated": "2023-08-21T23:20:50.52Z",
  "site": {
    "exposed-origins": ["https://www.example.com", "https://www.example.com"],
    "backend-origins": ["https://backend1.example.com", "https://backend2.example.com"]
  }
}

Note that this descriptor allows but is not sufficient to describe more complex arrangements; for example, different backend-origins for different URL path locations, or when one exposed-origin redirects all requests to the other.¶

3.2. Gateway Source Address Lists

The "gateway-sourcelists" descriptor is a JSON array of strings containing one or more URLs that can be used to fetch gateway source address lists.¶

Their URLs MUST have a scheme of "https". If multiple URLs are listed, their contents are combined to reconstruct the full list of source IP addresses for the gateway. Consumers SHOULD respect HTTP caching rules when fetching lists, refreshing their contents as necessary once they become stale.¶

For example:¶

{
  "description": "The Example CDN configuration for example.com",
  "generated": "2023-08-21T23:20:50.52Z",
  "gateway-sourcelists": [
    "https://cdn.example.com/source-addresess/ipv4",
    "https://cdn.example.com/source-addresses/ipv6"
  ]
}

Gateway source address lists are textual documents (with a RECOMMENDED media type of "text/plain") whose format is one entry per line, with all whitespace being ignored and all content on a line after the "#" being ignored. Each entry contains an IPv4 or IPv6 address block, using "/" notation.¶

For example:¶

# My IP addresses
192.0.2.0/24
  198.51.100.0/24   # TEST-NET-2

2001:db8::/32

... contains three entries, "192.0.2.0/24", "198.51.100.0/24", and "2001:db8::/32".¶

3.3. Gateway Header Authentication

The "gateway-header-auth" descriptor is a JSON array of two strings representing a HTTP header field name and value that it will send in all HTTP requests to the origin, allowing the origin to discriminate them from other requests.¶

For example:¶

{
  "description": "The Example CDN configuration for example.com",
  "generated": "2023-08-21T23:20:50.52Z",
  "gateway-header-auth": ["Secret", "my$ecret"]
}

would imply that the gateway would send this HTTP header field in all requests to the origin:¶

Secret: my$ecret

3.4. Forwarded Host

The "forwarded-host" descriptor is a boolean that indicates whether the Host request header field sent by the gateway is that which it received (one of the exposed origins) if true, or that of the backend origin selected if false.¶

For example:¶

{
  "description": "The Example CDN configuration for example.com",
  "generated": "2023-08-21T23:20:50.52Z",
  "forwarded-host": false
}

would imply that the gateway has rewritten the Host request header field will be rewritten to be that of the backend origin.¶

3.5. HTTP Methods Allowed

The "methods-allow" descriptor is a JSON array of case-sensitive strings that indicate the HTTP methods that the gateway will accept in requests, forwarding them to the backend origin or handling them locally as appropriate.¶

The value "*" indicates that unrecognised methods are forwarded to the backend origin server.¶

For example:¶

{
  "description": "The Example CDN configuration for example.com",
  "generated": "2023-08-21T23:20:50.52Z",
  "methods-allow": ["GET", "HEAD", "POST", "PUT", "DELETE", "OPTIONS"]
}

3.6. Targeted Cache Control

The "targeted-cc" descriptor is a JSON array of strings indicating the targeted cache-control header field(s) [TARGETED] supported by the gateway, in order of precedence (i.e., first entry overrides later entries)¶

For example:¶

{
  "description": "The Example CDN configuration for example.com",
  "generated": "2023-08-21T23:20:50.52Z",
  "targeted-cc": [
    "ExampleCDN-Cache-Control",
    "CDN-Cache-Control"
  ]
}

3.7. Invalidation API

The "invalidation-api" descriptor is a JSON object that contains information about the gateway's deployment of [INVALIDATION].¶

These objects can contain the following members and values:¶

• "uri": a string conveying the URI of the Invalidation Resource (Section 2 of [INVALIDATION])¶
• "selectors": an array of strings indicating the selectors (Section 3.1 of [INVALIDATION]) that the Invalidation Resource supports¶
• "purge": a boolean indicating whether the Invalidation Resource supports the "purge" member in requests (see Section 3 of [INVALIDATION])¶
• "p95-latency": an integer indicating the number of milliseconds that 95% of invalidation requests should be fully applied to the scope indicated by the description.¶

For example:¶

{
  "description": "The Example CDN configuration for example.com",
  "generated": "2023-08-21T23:20:50.52Z",
  "invalidation-api": {
    "uri": "https://api.cdn.example.com/invalidate",
    "selectors": ["uri", "uri-prefix", "group"],
    "purge": true,
    "p95-latency": 2000
  }
}

If the "api-auth" descriptor (Section 3.8) is present, the authentication details there SHOULD be sent on all requests to the invalidation API.¶

3.8. API Authentication

The "api-auth" descriptor is a string representing a Bearer HTTP authentication (Section 2.1 of [BEARER]) to be used to authenticate the backend origin in interaction with Gateway APIs.¶

For example:¶

{
  "description": "The Example CDN configuration for example.com",
  "generated": "2023-08-21T23:20:50.52Z",
  "bearer": "mF_9.B5f-4.1JqM"
}

3.9. Vendor Extensions

The "vendor" descriptor is a JSON object that can be use for gateway- and vendor-specific extensions to the format. Its members' names MUST be in internet hostname format, associating a name associated with the gateway and/or its vendor. The contents of member values are under the control of that party.¶

For example:¶

{
  "description": "The Example CDN configuration for example.com",
  "generated": "2023-08-21T23:20:50.52Z",
  "vendor": {
    "cdn.example.com": {
      "foo": "bar",
      "1": 2
    }
  }
}