startup

#!/usr/bin/perl
# Why perl?  I tried this with bash trap,
# and it wouldn't interrupt the docker run
# command below.  Perl seems to trap signals
# more reliably

use Socket;

# A name for the instance we're proxying
my $name = "$ENV{HOSTNAME}-instance";
my $PORT = $ENV{PORT};
my $DOCKER_RUN = $ENV{DOCKER_RUN};

# Trap TERM/INT from the proxy container 
# in order to stop our instance container
$SIG{INT} = \&stopper;
$SIG{TERM} = \&stopper;

my $cid = `docker run -d --name $name $DOCKER_RUN`;
chomp $cid;
print "Started container $cid\n";

# socat seems to segfault when redirecting to a DNS name...
# So look it up I guess.
$ip = inet_ntoa(inet_aton($name));

# Listen without forever on $PORT waiting for at least some input 
# before initiating connection. Each time the connection is terminated
# wait for a new one.
system("socat TCP-LISTEN:$PORT,fork TCP:$ip:$PORT &");

# Tail the logs, so that if the container dies, the proxy dies too
system("docker logs -f $name");

sub stopper()
{
  print "Stopping container $name\n";
  system("docker stop $name ; docker rm $name");
}