Standalone resque-web without a Rack server raises NoMethodError

[mishina2228]

I tried to run resque-web with minimal configuration but got an error.
Here is a minimal reproduce:

Gemfile:

source "https://rubygems.org"

gem 'resque'

Output:

$ bundle exec resque-web --foreground
[2022-09-20 22:10:34 +0900] Starting 'resque-web'...
[2022-09-20 22:10:34 +0900] trying port 5678...
[2022-09-20 22:10:34 +0900] Running with Rack handler: nil
bundler: failed to load command: resque-web (/home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/bin/resque-web)
/home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/resque-2.4.0/lib/resque/web_runner.rb:178:in `run!': undefined method `run' for nil:NilClass (NoMethodError)

      rack_handler.run app, :Host => host, :Port => port do |server|
                  ^^^^
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/resque-2.4.0/lib/resque/web_runner.rb:115:in `start'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/resque-2.4.0/lib/resque/web_runner.rb:48:in `initialize'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/resque-2.4.0/bin/resque-web:15:in `new'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/resque-2.4.0/bin/resque-web:15:in `<top (required)>'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/bin/resque-web:25:in `load'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/bin/resque-web:25:in `<top (required)>'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/cli/exec.rb:58:in `load'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/cli/exec.rb:58:in `kernel_load'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/cli/exec.rb:23:in `run'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/cli.rb:486:in `exec'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/vendor/thor/lib/thor/invocation.rb:127:in `invoke_command'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/vendor/thor/lib/thor.rb:392:in `dispatch'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/cli.rb:31:in `dispatch'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/vendor/thor/lib/thor/base.rb:485:in `start'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/cli.rb:25:in `start'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/exe/bundle:48:in `block in <top (required)>'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/lib/bundler/friendly_errors.rb:120:in `with_friendly_errors'
        from /home/owner/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/bundler-2.3.22/exe/bundle:36:in `<top (required)>'
        from /home/owner/.rbenv/versions/3.1.2/bin/bundle:25:in `load'
        from /home/owner/.rbenv/versions/3.1.2/bin/bundle:25:in `<main>'

This was due to the lack of a valid Rack server, as noted below.

[2022-09-20 22:10:34 +0900] Running with Rack handler: nil

resque/lib/resque/web_runner.rb

Lines 175 to 176 in daf45bb

	def run!
	logger.info "Running with Rack handler: #{@rack_handler.inspect}"

From the following source code, it seems that @app.server returns possible servers and
it is trying to see if they can be loaded.

resque/lib/resque/web_runner.rb

Lines 279 to 293 in daf45bb

	# If they aren't using our hook, try to use their @app.server settings
	elsif @app.respond_to?(:server) and @app.server
	# If :server isn't set, it returns an array of possibilities,
	# sorted from most to least preferable.
	if @app.server.is_a?(Array)
	handler = nil
	@app.server.each do |server|
	begin
	handler = Rack::Handler.get(server)
	break
	rescue LoadError, NameError
	next
	end
	end
	handler

Therefore, I added puma to the Gemfile and it works.

$ bundle exec resque-web --foreground
[2022-09-20 22:32:51 +0900] Starting 'resque-web'...
[2022-09-20 22:32:51 +0900] trying port 5678...
[2022-09-20 22:32:51 +0900] Running with Rack handler: Rack::Handler::Puma
Puma starting in single mode...
* Puma version: 5.6.5 (ruby 3.1.2-p20) ("Birdie's Version")
*  Min threads: 0
*  Max threads: 5
*  Environment: development
*          PID: 130995
* Listening on http://0.0.0.0:5678
Use Ctrl-C to stop

However, it took me a while to understand the cause of the problem and it would be nice to see the appropriate message.