Edge caching

API Mesh for Adobe Developer App Builder supports edge caching if you provide your own content delivery network (CDN), such as Fastly. Edge caching helps improve website load times and reduces consumption costs associated with bandwidth.

When using a CDN, you must invalidate the cache after modifying a mesh configuration or you will receive stale information.

Cache-control headers

A CDN's cache-control headers determine how queried information is cached.

When a browser or a GET request accesses a URL, the site's response headers typically include a cache-control header, which determines how long the site will allow its data to be cached. For example, a website could have the following response header:

cache-control: max-age=0
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cache-control: max-age=0

The max-age=0 cache-control directive means that this site wants to serve fresh data until 0 seconds after the response is generated, which basically means it never wants to cache data. This could also be achieved with a no-store directive.

For more information on specific cache-control directives and how they can be used, see the Mozilla Developer Network's cache control guide.

Using cache-control headers with API Mesh

API mesh users can add cache-control headers to request headers or to a mesh configuration file.

Currently, query-level caching is not supported.

As request headers

Use a mesh configuration similar to the example below to return forwarded headers.

You can also use a header value of x-include-metadata=true to return all headers.

When the response includes cache-control values, only the most restrictive values are returned.

{
  "meshConfig": {
    "responseConfig": {
        "headers": {
      "Cache-Control": "max-age=50,min-fresh=6,stale-if-error=20,public,must-revalidate"
        }
    },
    "sources": [
      {
        "name": "venia",
        "handler": {
          "graphql": {
            "endpoint": "https://venia.magento.com/graphql"
          }
        }
      }
    ]
  }
}
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{
  "meshConfig": {
    "responseConfig": {
        "headers": {
      "Cache-Control": "max-age=50,min-fresh=6,stale-if-error=20,public,must-revalidate"
        }
    },
    "sources": [
      {
        "name": "venia",
        "handler": {
          "graphql": {
            "endpoint": "https://venia.magento.com/graphql"
          }
        }
      }
    ]
  }
}

POST requests are not supported, and GET requests are limited to 2,048 characters.

How conflicting header values are resolved

When cache-control header values from multiple sources conflict, API Mesh selects the lowest or most restrictive value. The following section explains which values are returned when cache-control directives conflict.

The no-store directive supersedes all other directives. If your source's cache-control headers contain this directive, then the mesh does not return other headers.

If your source's cache-control headers contain conflicting values for the following directives, the mesh selects the lowest value:

min-fresh
max-age
max-stale
s-maxage
stale-if-error
stale-while-revalidate

If your source's cache-control headers contain any of the following directives, the mesh adds the directive to the cache-control response.

public
private
immutable
no-cache
no-transform
must-revalidate
proxy-revalidate
must-understand

Examples

The following example scenarios indicate the resulting Response header from two conflicting sources:

Example 1

Source 1 response headers
- max-age=3600, stale-while-revalidate=60, stale-if-error=3600
Source 2 response headers
- max-age:600, stale-if-error=60
Combined HTTP response headers
- max-age=600, stale-while-revalidate=60, stale-if-error=60

Example 2

Source 1 response headers
- max-age=3600, stale-while-revalidate=60, stale-if-error=3600
Source 2 response headers
- no-store
Combined HTTP response headers
- no-store

In the mesh configuration file

To set your own values for cache-control headers, add a Cache-Control key-value pair to the responseConfig object in your mesh configuration file.

Cache-control header values in your mesh configuration file take precedence over other conflicting values for your sources and are always included in the response.

Mesh Example

{
  "meshConfig": {
    "responseConfig": {
        "headers": {
      "Cache-Control": "max-age=50,min-fresh=6,stale-if-error=20,public,must-revalidate"
        }
    },
    "sources": [
      {
        "name": "venia",
        "handler": {
          "graphql": {
            "endpoint": "https://venia.magento.com/graphql"
          }
        }
      }
    ]
  }
}
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{
  "meshConfig": {
    "responseConfig": {
        "headers": {
      "Cache-Control": "max-age=50,min-fresh=6,stale-if-error=20,public,must-revalidate"
        }
    },
    "sources": [
      {
        "name": "venia",
        "handler": {
          "graphql": {
            "endpoint": "https://venia.magento.com/graphql"
          }
        }
      }
    ]
  }
}