KemaForkCorrect.cr

require "kemal"
require "logger"

log = Logger.new(STDERR)
log.level = Logger::DEBUG

get "/" do
  "Hello World! I am a process with pid #{Process.pid}"
end

sgnl_kemal_stop = Channel(Int32).new
spawn do
    Kemal.run { |cfg| cfg.server.not_nil!.bind(reuse_port: true) }
    sgnl_kemal_stop.send(1)
end

children_procs = [] of Process
15.times do
    children_procs << ( child_p = Process.fork do
        log.info("I am a child process with pid #{Process.pid}")
        Signal::TERM.trap do
            log.warn("Process #{Process.pid} received TERM signal, so we have to emergency cleanup and exit now")
            Kemal.stop
            exit(0)
        end
        exit_code = sgnl_kemal_stop.receive
        log.error("[#{Process.pid}] Ooops. How is that possible?")
        exit(1)
    end )
end

sgnl_sighup_rcvd = Channel(Int32).new
{% for sgnl in %w(HUP TERM INT) %}
Signal::{{sgnl.id}}.trap do
    sgnl_sighup_rcvd.send(1)
end
{% end %}

log.info( "I am a main process with pid #{Process.pid}. Send me HUP signal to terminate Kemal server gracefully" )

x = sgnl_sighup_rcvd.receive
log.info( "(some) signal received by master process #{Process.pid}. We have to terminate our children (by pid):\n\t[" + children_procs.map {|p| p.pid}.join(", ") + "]" )

children_procs.each do |child_p|
    child_pid = child_p.pid
    if child_p.terminated?
        log.warn( "Child ##{child_pid} already terminated" )
    else
        log.debug("Sending signal TERM (15) to process #{child_pid}")
        child_p.kill
        child_p.wait
    end
    log.error( "Cant terminate child ##{child_pid}" ) unless child_p.terminated?
end

Kemal.stop