pbot/applets/compiler_vm/host/bin/vm-server

#!/usr/bin/env perl

# File: vm-server
#
# Purpose: The compiler server manages the guest virtual machine state and
# listens for incoming compile requests. This server can be run on any remote
# machine. There can be multiple servers using different ports on the same machine.
#
# SPDX-FileCopyrightText: 2021 Pragmatic Software <pragma78@gmail.com>
# SPDX-License-Identifier: MIT

use warnings;
use strict;

use IO::Socket;
use Net::hostent;
use IPC::Shareable;
use Time::HiRes qw/gettimeofday/;
use Encode;

use constant {
    SERVER_PORT     => 9000,
    SERIAL_PORT     => 5555,
    HEARTBEAT_PORT  => 5556,
    DOMAIN_NAME     => 'pbot-vm',
    COMPILE_TIMEOUT => 10,
};

sub vm_stop {
    system('virsh shutdown ' . DOMAIN_NAME);
}

sub vm_start {
    system('virsh start ' . DOMAIN_NAME);
}

sub vm_reset {
    return if $ENV{NORESET};
    system('virsh snapshot-revert '.DOMAIN_NAME.' 1');
    print "Reset vm\n";
}

sub execute {
    my ($cmdline) = @_;

    print "execute($cmdline)\n";

    my @list = split / /, $cmdline;

    my ($ret, $result);

    my $child = fork;

    if($child == 0) {
        ($ret, $result) = eval {
            my $result = '';

            my $pid = open(my $fh, '-|', @list);

            if (not defined $pid) {
                print "Couldn't fork: $!\n";
                return (-13, "[Fatal error]");
            }

            local $SIG{ALRM} = sub { kill 9, $pid; die "Timed-out: $result\n"; };
            alarm(COMPILE_TIMEOUT);

            print "Reading result...\n";
            while (my $line = <$fh>) {
                print "read result [$line]\n";
                $result .= $line;
            }

            close $fh;
            print "Done reading result.\n";

            my $ret = $? >> 8;

            print "[$ret, $result]\n";
            return ($ret, $result);
        };

        alarm 0;
        if ($@ =~ /Timed-out: (.*)/) {
            return (-13, "[Timed-out] $1");
        }

        return ($ret, $result);
    } else {
        waitpid($child, 0);
        print "?: $?\n";
        my $result = $? >> 8;
        print "child exited, parent continuing [result = $result]\n";
        return (undef, $result);
    }
}

sub connect_to_heartbeat {
    my $heartbeat;
    my $attempts = 15;

    while (!$heartbeat && $attempts > 0) {
        print "Connecting to heartbeat ... ";

        $heartbeat = IO::Socket::INET->new (
            PeerAddr => '127.0.0.1',
            PeerPort => HEARTBEAT_PORT,
            Proto    => 'tcp',
            Type     => SOCK_STREAM,
        );

        if (!$heartbeat) {
            print "failed.\n";
            --$attempts;
            print "Trying again in 2 seconds ($attempts attempts remaining) ...\n" if $attempts > 0;
            sleep 2;
        } else {
            print "success!\n";
        }
    }

    return $heartbeat;
}

sub server_listen {
    my $port = shift @_;
    my $server = IO::Socket::INET->new (
        Proto     => 'tcp',
        LocalPort => $port,
        Listen    => SOMAXCONN,
        ReuseAddr => 1,
        Reuse     => 1,
    );
    die "Can't setup server: $!" unless $server;
    print "[Server $0 accepting clients at :$port]\n";
    return $server;
}

sub vm_server {
    my ($server, $heartbeat_pid, $heartbeat_monitor);

    my $heartbeat;
    my $running;

    tie $heartbeat, 'IPC::Shareable', 'dat1', { create => 1 };
    tie $running,   'IPC::Shareable', 'dat2', { create => 1 };

    my $last_wait = 0;

    $running = 1;
    $heartbeat = 0;

    vm_reset;
    print "vm started\n";

    $heartbeat_pid = fork;
    die "Fork failed: $!" if not defined $heartbeat_pid;

    if ($heartbeat_pid == 0) {
        # heartbeat

        tie $heartbeat, 'IPC::Shareable', 'dat1', { create => 1 };
        tie $running,   'IPC::Shareable', 'dat2', { create => 1 };

        if (!($heartbeat_monitor = connect_to_heartbeat)) {
            die "Could not start heartbeat.\n";
        }

        print "child: running: $running\n";

        while($running and <$heartbeat_monitor>) {
            $heartbeat = 1;
            #print "child: got heartbeat\n";
        }

        $heartbeat = -1;
        print "child no longer running\n";

        exit;

    } else {
        # server

        if (not defined $server) {
            print "Starting compiler server on port " . SERVER_PORT . "\n";
            $server = server_listen(SERVER_PORT);
        } else {
            print "Compiler server already listening on port " . SERVER_PORT . "\n";
        }

        print "parent: running: $running\n";

        while ($running and my $client = $server->accept) {
            $client->autoflush(1);
            my $hostinfo = gethostbyaddr($client->peeraddr);

            print '-' x 20, "\n";
            printf "[Connect from %s at %s]\n", $client->peerhost, scalar localtime;

            my ($timed_out, $killed);

            eval {
                local $SIG{ALRM} = sub { die 'Timed-out'; };
                alarm 5;

                while (my $line = <$client>) {
                    $line =~ s/[\r\n]+$//;
                    next if $line =~ m/^\s*$/;
                    alarm 5;
                    print "got: [$line]\n";

                    if($heartbeat <= 0) {
                        print "No heartbeat yet, ignoring compile attempt.\n";
                        print $client "Recovering from previous snippet, please wait.\n" if gettimeofday - $last_wait > 60;
                        $last_wait = gettimeofday;
                        last;
                    }

                    print "Attempting compile...\n";
                    alarm 0;

                    my ($ret, $result) = execute("perl vm-exec $line");

                    if(not defined $ret) {
                        #print "parent continued\n";
                        print "parent continued [$result]\n";
                        $timed_out = 1 if $result == 243 or $result == -13; # -13 == 243
                        $killed = 1 if $result == 242 or $result == -14; # -14 = 242
                        last;
                    }

                    $result =~ s/\s+$//;
                    print "Ret: $ret; result: [$result]\n";

                    if($result =~ m/\[Killed\]$/) {
                        print "Process was killed\n";
                        $killed = 1;
                    }

                    print $client $result . "\n";
                    close $client;

                    $ret = -14 if $killed;

                    # child exit
                    print "child exit\n";
                    exit $ret;
                }

                alarm 0;
            };

            alarm 0;

            close $client;

            print "timed out: $timed_out; killed: $killed\n";
            next unless ($timed_out or $killed);

            vm_reset;
            next;

            print "stopping vm\n";
            #vm_stop;
            $running = 0;
            last;
        }

        print "Compiler server no longer running, restarting...\n";
    }

    print "waiting on heartbeat pid\n";
    waitpid($heartbeat_pid, 0);
}

vm_server;