Control_Forks.cr

require "logger"
TMPDIR = "/tmp/proc_respawn"
Signal::USR1.trap do
        puts "parent(SIGUSR1): catched"
end

Signal::CHLD.trap do
        puts "parent(SIGCHLD): forked proc exited"
end

i = 0
children = (1..5).map do |proc_n|
    puts "parent: spawn child ##{proc_n}"
    Process.fork do
        puts "child##{Process.pid}: starting"
        wait4file = "#{TMPDIR}/#{proc_n}"
        begin
            loop do
                if File.exists?(wait4file)
                    puts "child##{Process.pid}: my file is here, so raising exception"
                    raise ""
                end
                sleep 1
            end
        rescue
            File.delete(wait4file) if File.exists?(wait4file)
            Process.kill(Signal::USR1, Process.ppid)
            exit(1)
        end
    end
end


sgnl_sigexit_rcvd = Channel(Nil).new
sgnl_sigchld_rcvd = Channel(Nil).new

{% for sgnl in %w(HUP TERM INT) %}
Signal::{{sgnl.id}}.trap do
        sgnl_sigexit_rcvd.send(nil)
end
{% end %}

spawn do
    sgnl_sighup_rcvd.receive

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

    children.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
end

loop do
        sgnl_sigchld_rcvd.receive
end