Webhook Relay
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Edit request/response
In this page we will demonstrate basic operations that you can achieve in functions.

Accessing request data (incoming webhook/API request)

Lua functions use r object that provide access to request data (headers, query, method and body) and can then update any HTTP request details.
Available data to access:
Method name
Type
Description
r.RequestBody
String
Request body.
r.RequestMethod
String
Request method (PUT, POST, DELETE, etc.).
r.RequestPath
String
Request path.
r.RequestRawQuery
String
Request query, for example if the request was made with /api?category=electronics, then the query will be category=electronics.
r.RequestHeader
Table
A table [foo]bar of headers.
r.RequestQuery
Table
A table [foo]bar of query.

Read request body

An example of accessing request body and decoding it:
-- import json package
local json = require("json")
-- request body is in r.RequestBody, use it as any other string:
local body, err = json.decode(r.RequestBody)
if err then error(err) end

Reading request headers

To access specific header, use:
local my_header = r.RequestHeader["Your-Header-Name"]

Reading request URL query

To read request URL query (for example /v1/api?hub.mode=subscribe&hub.challenge=1903260781&hub.verify_token=my-token") you have two options:
  1. 1.
    r.RequestQuery["hub.challenge"] which will return 1903260781 for this example.
  2. 2.
    r.RequestRawQuery which will return full raw query hub.mode=subscribe&hub.challenge=1903260781&hub.verify_token=my-token"

Modify request data

Available methods to update request:
Method name
Parameter Type
Description
r:SetRequestBody(“string”)
String
Update request body
r:SetRequestMethod(“string”)
String
Update request method
r:SetRequestRawQuery(“foo=bar”)
String
Update request raw query
r:SetRequestPath(“/extra/path”)
String
Set additional extra path
r:DeleteRequestHeader("key")
String
Delete header
r:SetRequestHeader(“key”, “value”)
String, String
Set new header key/value pair
An example how to update request object:
-- set body
r:SetRequestBody("new body")
-- set method
r:SetRequestMethod("string")
-- set raw query
r:SetRequestRawQuery("foo=bar")
-- set extra path
r:SetRequestPath("/extra/path")
-- set header
r:SetRequestHeader("Content-Type", "application/json")
-- delete header
r:DeleteRequestHeader("Very-Secret")

Modify response

Note: customized responses only applicable if function is attached to the Input and not bucket’s Output.
Available methods to set customized response:
Method name
Parameter Type
Description
r:SetResponseBody(“string”)
String
Set response body
r:SetResponseStatusCode(201)
Integer
Set response status code
r:SetResponseHeader(“key”, “value”)
String, String
Set response header key/value pair

Getting configuration values

Configuration values in Lua functions allow sharing the code without sharing sensitive information or just configuration values that might change between accounts, teams, etc.
To add a new configuration value:
  1. 1.
    Create a function
  2. 2.
    Go to function details
  3. 3.
    Click on a tab “CONFIG VARIABLES”
  4. 4.
    Specify config variable key and value.
Once you have specified these details, you can start using them in your functions:
-- configuration is accessible from a global "cfg" variable
local project_id = cfg:GetValue("PROJECT_ID")
-- do something with the value

Filtering requests

To filter requests based on body, headers or some external conditions, you can use r:StopForwarding() method. This will set webhook status to rejected and this webhook will not be forwarded:
-- in this example we will check the payload to make the decision
local json = require("json")
-- incoming request body example:
-- {
-- "action": "important",
-- "user": "joe"
-- }
local requestBody, err = json.decode(r.RequestBody)
if err then error(err) end
-- simple comparison of the payload
if requestBody["action"] == "not_important" then
-- request is not important, don't forward it
r:StopForwarding()
return
end
-- Otherwise, continue forwarding or add any additional logic here