Background
Currently, response-rewrite plugin only supports set / delete headers.
The limitation makes some operations impossible. For example, we can't
add a Set-Cookie header in APISIX as it may override the Set-Cookie
header from the upstream.
Therefore, we need a way to add a header without overriding the existing one.
Solution
We can enrich the headers field and add the operation name to it. Here
is the new configuration schema:
headers = {
description = "new headers for response",
anyOf = {
{
type = "object",
minProperties = 1,
patternProperties = {
["^[^:]+$"] = {
oneOf = {
{type = "string"},
{type = "number"},
}
}
},
},
{
properties = {
add = {
type = "array",
minItems = 1,
items = {
type = "string",
-- "Set-Cookie: <cookie-name>=<cookie-value>;
Max-Age=<number>"
pattern = "^[^:]+:[^:]+$"
}
},
set = {
type = "object",
minProperties = 1,
patternProperties = {
["^[^:]+$"] = {
oneOf = {
{type = "string"},
{type = "number"},
}
}
},
},
remove = {
type = "array",
minItems = 1,
items = {
type = "string",
-- "Set-Cookie"
pattern = "^[^:]+$"
}
},
}
}
}
},
set means rewriting the headers,
remove means removing the headers,
addmeans appending the new headers.
For set and add, the header format is "name: value", while for remove,
the format is "name".
We use array to represent multiple headers, so the same header can be
used multiple times in the add. For example,
add = {
"Cache-Control: no-cache",
"Cache-Control: max-age=0, must-revalidate"
}
The previous configuration can be migrated as part of the new configuration.
The execution order among those operations are ["add", "set", "remove"].
Inspired by:
https://istio.io/latest/docs/reference/config/networking/virtual-service/#Headers-HeaderOperations
https://docs.konghq.com/hub/kong-inc/response-transformer/
