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[wip/proposal] fix(pdk): service.response.get_headers behavior #13827

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[wip/proposal] fix(pdk): service.response.get_headers behavior #13827

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119 changes: 21 additions & 98 deletions kong/pdk/service/response.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -36,90 +36,25 @@ local header_body_log = phase_checker.new(PHASES.response,
PHASES.body_filter,
PHASES.log)


local attach_resp_headers_mt

local clear_non_upstream_headers

do
local resp_headers_orig_mt_index


local resp_headers_mt = {
__index = function(t, name)
if type(name) == "string" then
local var = fmt("upstream_http_%s", replace_dashes_lower(name))
if not ngx.var[var] then
return nil
end
-- pairs in a hot code path - although this hits an NYI and falls back to the
-- interpreter, it uses an optimized hand-written assembly form of loop on table
-- that does not use `next`
clear_non_upstream_headers = function (response_headers, err)
for header_name, _ in pairs(response_headers) do
local var = fmt("upstream_http_%s", replace_dashes_lower(header_name))
if not ngx.var[var] then
response_headers[header_name] = nil
end

return resp_headers_orig_mt_index(t, name)
end,
}


attach_resp_headers_mt = function(response_headers, err)
if not resp_headers_orig_mt_index then
local mt = getmetatable(response_headers)
resp_headers_orig_mt_index = mt.__index
end

setmetatable(response_headers, resp_headers_mt)

return response_headers, err
end
end


local attach_buffered_headers_mt

do
local EMPTY = {}

attach_buffered_headers_mt = function(response_headers, max_headers)
if not response_headers then
return EMPTY
end

return setmetatable({}, { __index = function(_, name)
if type(name) ~= "string" then
return nil
end

if response_headers[name] then
return response_headers[name]
end

name = lower(name)

if response_headers[name] then
return response_headers[name]
end

name = replace_dashes(name)

if response_headers[name] then
return response_headers[name]
end

local i = 1
for n, v in pairs(response_headers) do
if i > max_headers then
return nil
end

n = replace_dashes_lower(n)
if n == name then
return v
end

i = i + 1
end
end })
end
end


local function new(pdk, major_version)
local response = {}

Expand All @@ -137,8 +72,8 @@ local function new(pdk, major_version)
local MIN_HEADERS = 1
local MAX_HEADERS_DEFAULT = 100
local MAX_HEADERS = 1000
local MAX_HEADERS_CONFIGURED

local MAX_HEADERS_CONFIGURED = pdk.configuration and pdk.configuration.lua_max_resp_headers
or MAX_HEADERS_DEFAULT

---
-- Returns the HTTP status code of the response from the Service as a Lua number.
Expand Down Expand Up @@ -196,39 +131,27 @@ local function new(pdk, major_version)
-- kong.log.inspect(headers.x_another[1]) -- "foo bar"
-- kong.log.inspect(headers["X-Another"][2]) -- "baz"
-- end
-- Note that this function returns a proxy table
-- which cannot be iterated with `pairs` or used as operand of `#`.
function response.get_headers(max_headers)
check_phase(header_body_log)

local buffered_headers = ngx.ctx.buffered_headers

if max_headers == nil then
if buffered_headers then
if not MAX_HEADERS_CONFIGURED then
MAX_HEADERS_CONFIGURED = pdk and pdk.configuration and pdk.configuration.lua_max_resp_headers
end
return attach_buffered_headers_mt(buffered_headers, MAX_HEADERS_CONFIGURED or MAX_HEADERS_DEFAULT)
end

return attach_resp_headers_mt(ngx.resp.get_headers())
end
if max_headers ~= nil and type(max_headers) ~= "number" then
error("max_headers must be a number or nil", 2)

if type(max_headers) ~= "number" then
error("max_headers must be a number", 2)

elseif max_headers < MIN_HEADERS then
elseif max_headers and max_headers < MIN_HEADERS then
error("max_headers must be >= " .. MIN_HEADERS, 2)

elseif max_headers > MAX_HEADERS then
elseif max_headers and max_headers > MAX_HEADERS then
error("max_headers must be <= " .. MAX_HEADERS, 2)
end

if buffered_headers then
return attach_buffered_headers_mt(buffered_headers, max_headers)
local ctx = ngx.ctx
if ctx.buffered_proxying and ctx.buffered_headers then
-- XXX ensure metatable is the same as for non-buffered
return ctx.buffered_headers
end

return attach_resp_headers_mt(ngx.resp.get_headers(max_headers))
-- we patch ngx.resp.get_headers to honor the max headers kong config
return clear_non_upstream_headers(ngx.resp.get_headers(max_headers))
end

---
Expand Down
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