feat(aws-lambda) Add support for setting the unhandled response code

Adds a new `unhandled_status` configuration option for the aws-lambda
plugin. If set the response status will be overridden if the
`X-Amzn-Function-Error` lambda invoke respoonse header was set to
`Unhandled`.

This gives a new feature to users of the plugin allowing their API to
return non 20x codes. The previous functionality of responding with
Amazon's Lambda Invoke unhandled response status of 200 (RequestResponse),
202 (Event), or 204 (DryRun) remains.

kong/plugins/aws-lambda/handler.lua

@@ -83,7 +83,14 @@ function AWSLambdaHandler:access(conf)
     return responses.send_HTTP_INTERNAL_SERVER_ERROR(err)
   end
 
-  ngx.status = res.status
+  if conf.unhandled_status
+     and headers["X-Amzn-Function-Error"] == "Unhandled"
+  then
+    ngx.status = conf.unhandled_status
+
+  else
+    ngx.status = res.status
+  end
 
   -- Send response to client
   for k, v in pairs(headers) do

kong/plugins/aws-lambda/schema.lua

@@ -1,3 +1,11 @@
+local function check_status(status)
+  if status and (status < 100 or status > 999) then
+    return false, "unhandled_status must be within 100 - 999."
+  end
+
+  return true
+end
+
 return {
   fields = {
     timeout = {type = "number", default = 60000, required = true },
@@ -14,5 +22,6 @@ return {
     log_type = {type = "string", required = true, default = "Tail", 
                        enum = {"Tail", "None"}},
     port = { type = "number", default = 443 },
+    unhandled_status = { type = "number", func = check_status },
   }
 }

spec/03-plugins/23-aws-lambda/01-access_spec.lua

@@ -28,6 +28,30 @@ describe("Plugin: AWS Lambda (access)", function()
       upstream_url = "http://httpbin.org"
     })
 
+    local api5 = assert(helpers.dao.apis:insert {
+      name = "lambda5.com",
+      hosts = { "lambda5.com" },
+      upstream_url = "http://httpbin.org"
+    })
+
+    local api6 = assert(helpers.dao.apis:insert {
+      name = "lambda6.com",
+      hosts = { "lambda6.com" },
+      upstream_url = "http://httpbin.org"
+    })
+
+    local api7 = assert(helpers.dao.apis:insert {
+      name = "lambda7.com",
+      hosts = { "lambda7.com" },
+      upstream_url = "http://httpbin.org"
+    })
+
+    local api8 = assert(helpers.dao.apis:insert {
+      name = "lambda8.com",
+      hosts = { "lambda8.com" },
+      upstream_url = "http://httpbin.org"
+    })
+
     assert(helpers.dao.plugins:insert {
       name = "aws-lambda",
       api_id = api1.id,
@@ -79,6 +103,57 @@ describe("Plugin: AWS Lambda (access)", function()
       }
     })
 
+    assert(helpers.dao.plugins:insert {
+      name = "aws-lambda",
+      api_id = api5.id,
+      config = {
+        port = 10001,
+        aws_key = "mock-key",
+        aws_secret = "mock-secret",
+        aws_region = "us-east-1",
+        function_name = "functionWithUnhandledError",
+      }
+    })
+
+    assert(helpers.dao.plugins:insert {
+      name = "aws-lambda",
+      api_id = api6.id,
+      config = {
+        port = 10001,
+        aws_key = "mock-key",
+        aws_secret = "mock-secret",
+        aws_region = "us-east-1",
+        function_name = "functionWithUnhandledError",
+        invocation_type = "Event",
+      }
+    })
+
+    assert(helpers.dao.plugins:insert {
+      name = "aws-lambda",
+      api_id = api7.id,
+      config = {
+        port = 10001,
+        aws_key = "mock-key",
+        aws_secret = "mock-secret",
+        aws_region = "us-east-1",
+        function_name = "functionWithUnhandledError",
+        invocation_type = "DryRun",
+      }
+    })
+
+    assert(helpers.dao.plugins:insert {
+      name = "aws-lambda",
+      api_id = api8.id,
+      config = {
+        port = 10001,
+        aws_key = "mock-key",
+        aws_secret = "mock-secret",
+        aws_region = "us-east-1",
+        function_name = "functionWithUnhandledError",
+        unhandled_status = 412,
+      }
+    })
+
     assert(helpers.start_kong{
       nginx_conf = "spec/fixtures/custom_nginx.template",
     })
@@ -109,6 +184,7 @@ describe("Plugin: AWS Lambda (access)", function()
     local body = assert.res_status(200, res)
     assert.is_string(res.headers["x-amzn-RequestId"])
     assert.equal([["some_value1"]], body)
+    assert.is_nil(res.headers["X-Amzn-Function-Error"])
   end)
   it("invokes a Lambda function with POST params", function()
     local res = assert(client:send {
@@ -208,4 +284,48 @@ describe("Plugin: AWS Lambda (access)", function()
     assert.res_status(500, res)
   end)
 
+  it("invokes a Lambda function with an unhandled function error (and no unhandled_status set)", function()
+    local res = assert(client:send {
+      method = "GET",
+      path = "/get?key1=some_value1&key2=some_value2&key3=some_value3",
+      headers = {
+        ["Host"] = "lambda5.com"
+      }
+    })
+    assert.res_status(200, res)
+    assert.equal("Unhandled", res.headers["X-Amzn-Function-Error"])
+  end)
+  it("invokes a Lambda function with an unhandled function error with Event invocation type", function()
+    local res = assert(client:send {
+      method = "GET",
+      path = "/get?key1=some_value1&key2=some_value2&key3=some_value3",
+      headers = {
+        ["Host"] = "lambda6.com"
+      }
+    })
+    assert.res_status(202, res)
+    assert.equal("Unhandled", res.headers["X-Amzn-Function-Error"])
+  end)
+  it("invokes a Lambda function with an unhandled function error with DryRun invocation type", function()
+    local res = assert(client:send {
+      method = "GET",
+      path = "/get?key1=some_value1&key2=some_value2&key3=some_value3",
+      headers = {
+        ["Host"] = "lambda7.com"
+      }
+    })
+    assert.res_status(204, res)
+    assert.equal("Unhandled", res.headers["X-Amzn-Function-Error"])
+  end)
+  it("invokes a Lambda function with an unhandled function error", function()
+    local res = assert(client:send {
+      method = "GET",
+      path = "/get?key1=some_value1&key2=some_value2&key3=some_value3",
+      headers = {
+        ["Host"] = "lambda8.com"
+      }
+    })
+    assert.res_status(412, res)
+    assert.equal("Unhandled", res.headers["X-Amzn-Function-Error"])
+  end)
 end)

spec/03-plugins/23-aws-lambda/02-schema_spec.lua

@@ -0,0 +1,46 @@
+local aws_lambda_schema = require "kong.plugins.aws-lambda.schema"
+local schemas = require "kong.dao.schemas_validation"
+local utils = require "kong.tools.utils"
+local validate_entity = schemas.validate_entity
+
+describe("Plugin: AWS Lambda (schema)", function()
+  local DEFAULTS = {
+    timeout = 60000,
+    keepalive = 60000,
+    aws_key = "my-key",
+    aws_secret = "my-secret",
+    aws_region = "us-east-1",
+    function_name = "my-function",
+    invocation_type  = "RequestResponse",
+    log_type = "Tail",
+    port  = 443,
+  }
+
+  it("accepts nil Unhandled Response Status Code", function()
+    local entity = utils.table_merge(DEFAULTS, { unhandled_status = nil })
+    local ok, err = validate_entity(entity, aws_lambda_schema)
+    assert.is_nil(err)
+    assert.True(ok)
+  end)
+
+  it("accepts correct Unhandled Response Status Code", function()
+    local entity = utils.table_merge(DEFAULTS, { unhandled_status = 412 })
+    local ok, err = validate_entity(entity, aws_lambda_schema)
+    assert.is_nil(err)
+    assert.True(ok)
+  end)
+
+  it("errors with Unhandled Response Status Code less than 100", function()
+    local entity = utils.table_merge(DEFAULTS, { unhandled_status = 99 })
+    local ok, err = validate_entity(entity, aws_lambda_schema)
+    assert.equal("unhandled_status must be within 100 - 999.", err.unhandled_status)
+    assert.False(ok)
+  end)
+
+  it("errors with Unhandled Response Status Code greater than 999", function()
+    local entity = utils.table_merge(DEFAULTS, { unhandled_status = 1000 })
+    local ok, err = validate_entity(entity, aws_lambda_schema)
+    assert.equal("unhandled_status must be within 100 - 999.", err.unhandled_status)
+    assert.False(ok)
+  end)
+end)

spec/fixtures/custom_nginx.template

@@ -275,6 +275,9 @@ http {
             content_by_lua_block {
                 local function say(res, status)
                   ngx.header["x-amzn-RequestId"] = "foo"
+                  if string.match(ngx.var.uri, "functionWithUnhandledError") then
+                    ngx.header["X-Amzn-Function-Error"] = "Unhandled"
+                  end
                   ngx.status = status
 
                   if type(res) == 'string' then