require 'kramdown'
# Handles mimicing of API Gateway to Lambda function call locally
module Jets::Controller::Middleware
class Local
extend Memoist
def initialize(app)
@app = app
end
def call(env)
route = RouteMatcher.new(env).find_route
unless route
return [404, {'Content-Type' => 'text/html'}, not_found(env)]
end
mimic = MimicAwsCall.new(route, env)
# Make @controller and @meth instance available so we dont not have to pass it around.
@controller, @meth, @event = mimic.controller, mimic.meth, mimic.event
if route.to == 'jets/rack#process' # megamode
# Bypass the Jets middlewares since it could interfere with the Rack
# application's middleware stack.
#
# Rails sends back a transfer-encoding=chunked. Curling Rails directly works,
# but passing the Rails response back through this middleware results in errors.
# Disable chunking responses by deleting the transfer-encoding response header.
# Would like to understand why this happens this better, if someone can explain please let me know.
status, headers, body = @controller.dispatch! # jets/rack_controller
headers.delete "transfer-encoding"
[status, headers, body]
elsif route.to == 'jets/mount#call' # mount route
status, headers, body = @controller.dispatch! # jets/mount_controller
[status, headers, body]
elsif polymorphic_function?
run_polymophic_function
else # Normal Jets request
mimic_aws_lambda!(env, mimic.vars) unless on_aws?(env)
@app.call(env)
end
end
# Never hit when calling polymorphic function on AWS Lambda. Can only get called with the local server.
def polymorphic_function?
return false if ENV['_HANDLER'] # slight speed improvement on Lambda
polymorphic_function.task.lang != :ruby
end
def polymorphic_function
# Abusing PolyFun to run polymorphic code, should call LambdaExecutor directly
# after reworking LambdaExecutor so it has a better interface.
Jets::PolyFun.new(@controller.class, @meth)
end
memoize :polymorphic_function
def run_polymophic_function
resp = polymorphic_function.run(@event, @meth) # polymorphic code
status = resp['statusCode']
headers = resp['headers']
body = StringIO.new(resp['body'])
[status, headers, body] # triplet
end
# Modifies env the in the same way real call from AWS lambda would modify env
def mimic_aws_lambda!(env, vars)
env.merge!(vars)
env
end
def on_aws?(env)
return false if Jets.env.test? # usually with test we're passing in full API Gateway fixtures with the HTTP_X_AMZN_TRACE_ID
return false if ENV['JETS_ELB'] # If we're using an ELB and Jets is inside a container running jets server, we don't want to pretend we're on AWS.
on_cloud9 = !!(env['HTTP_HOST'] =~ /cloud9\..*\.amazonaws\.com/)
!!env['HTTP_X_AMZN_TRACE_ID'] && !on_cloud9
end
def routes_error_message(env)
message = "404 Error: Route #{env['PATH_INFO'].sub('/','')} not found
"
if Jets.env != "production"
message << "Here are the routes defined in your application:
"
message << "#{routes_table}"
end
message
end
def not_found(env)
message = routes_error_message(env)
body = <<~HTML
Route not found
#{message}
HTML
StringIO.new(body)
end
# Show pretty route table for user to help with debugging in non-production mode
def routes_table
routes = Jets::Router.routes
return "Your routes table is empty." if routes.empty?
text = "Verb | Path | Controller#action\n"
text << "--- | --- | ---\n"
routes.each do |route|
text << "#{route.method} | #{route.path} | #{route.to}\n"
end
html = Kramdown::Document.new(text).to_html
puts html
html
end
end
end