lambdakiq invocation fails with "undefined method `each` for `nil:NilClass`

xeger commented 2 years ago

I'm using Lamby with a non-Rails Rack app. It's been working exceptionally well for me. I'm experimenting with lambakiq for background jobs and I've hit on a minor snag. I can easily monkey patch Lamby, but I wanted to give you a heads-up in case I'm doing something wrong.

The problem

When Lamby::Handler#call_handler instance method detects an SQS event, it doesn't return a proper Rack triple. This means that the handler's @body becomes null when #call assigns the return value to @status, @headers, @body.

Lamby::Handler.call class method finishes by calling #response on the handler instance, which assumes that @body is non-nil. However, for Lambdakiq events, it's always nil!

It seems like Lamby will therefore crash 100% of the time when Lamby.handler is used to dispatch the event. Am I missing something?

The gory details

My handler

This is pretty vanilla; although I'm using Praxis, not Rails, my $app is still a Rack app and the handler is byte-for-byte identical to the Lambdakiq README.

$app = Praxis::Application.instance.setup

def handler(event:, context:)
  Lamby.handler $app, event, context
end

Backtrace + Lambda error report

{
    "errorMessage": "undefined method `each' for nil:NilClass",
    "errorType": "Function<NoMethodError>",
    "stackTrace": [
        "/opt/ruby/gems/2.7.0/gems/lamby-3.1.1/lib/lamby/handler.rb:43:in `block in body'",
        "/opt/ruby/gems/2.7.0/gems/lamby-3.1.1/lib/lamby/handler.rb:42:in `tap'",
        "/opt/ruby/gems/2.7.0/gems/lamby-3.1.1/lib/lamby/handler.rb:42:in `body'",
        "/opt/ruby/gems/2.7.0/gems/lamby-3.1.1/lib/lamby/handler.rb:23:in `response'",
        "/opt/ruby/gems/2.7.0/gems/lamby-3.1.1/lib/lamby/handler.rb:7:in `call'",
        "/opt/ruby/gems/2.7.0/gems/lamby-3.1.1/lib/lamby.rb:25:in `handler'",
        "/var/task/handler.rb:30:in `handler'"
    ]
}

metaskills commented 2 years ago

Yup! Good bug report. When I added the Lambdakiq handler I failed to test it because I would have had to copy a few things over from the Lambdakiq gem. I was lazy... but did the work now in the #121 pull request. If those tests pass, I will do a tiny version bump and cut a new release. Again, thanks!!!

metaskills commented 2 years ago

Pushed v3.1.2. Lemme know how that does for you.

xeger commented 2 years ago

Works like a charm; thank you so much for the quick response, @metaskills!

I found an unrelated minor SNAFU in lambdakiq; will file an issue there.

rails-lambda / lamby