#! @perl@ -w
use strict;
use Fcntl ':flock';
use English '-no_match_vars';
# General operation:
#
# Try to find a free machine of type $neededSystem. We do this as
# follows:
# - We acquire an exclusive lock on $currentLoad/main-lock.
# - For each machine $machine of type $neededSystem and for each $slot
# less than the maximum load for that machine, we try to get an
# exclusive lock on $currentLoad/$machine-$slot (without blocking).
# If we get such a lock, we send "accept" to the caller. Otherwise,
# we send "postpone" and exit.
# - We release the exclusive lock on $currentLoad/main-lock.
# - We perform the build on $neededSystem.
# - We release the exclusive lock on $currentLoad/$machine-$slot.
#
# The nice thing about this scheme is that if we die prematurely, the
# locks are released automatically.
my $loadIncreased = 0;
my ($amWilling, $localSystem, $neededSystem, $drvPath, $mustRun) = @ARGV;
$mustRun = 0 unless defined $mustRun;
sub sendReply {
my $reply = shift;
open OUT, ">&3" or die;
print OUT "$reply\n";
close OUT;
}
sub decline {
sendReply "decline";
exit 0;
}
my $currentLoad = $ENV{"NIX_CURRENT_LOAD"};
decline unless defined $currentLoad;
mkdir $currentLoad, 0777 or die unless -d $currentLoad;
my $conf = $ENV{"NIX_REMOTE_SYSTEMS"};
decline if !defined $conf || ! -e $conf;
my $canBuildLocally = $amWilling && ($localSystem eq $neededSystem);
# Otherwise find a willing remote machine.
my @machines;
my %curJobs;
# Read the list of machines.
open CONF, "< $conf" or die;
while (<CONF>) {
chomp;
s/\#.*$//g;
next if /^\s*$/;
/^\s*(\S+)\s+(\S+)\s+(\S+)\s+(\d+)\s*$/ or die;
push @machines,
{ hostName => $1
, systemType => $2
, sshKeys => $3
, maxJobs => $4
};
}
close CONF;
# Acquire the exclusive lock on $currentLoad/main-lock.
my $mainLock = "$currentLoad/main-lock";
open MAINLOCK, ">>$mainLock" or die;
flock(MAINLOCK, LOCK_EX) or die;
# Find a suitable system.
my $rightType = 0;
my $machine;
LOOP: foreach my $cur (@machines) {
if ($neededSystem eq $cur->{systemType}) {
$rightType = 1;
# We have a machine of the right type. Try to get a lock on
# one of the machine's lock files.
my $slot = 0;
while ($slot < $cur->{maxJobs} || ($mustRun && !$canBuildLocally)) {
my $slotLock = "$currentLoad/" . $cur->{systemType} . "-" . $cur->{hostName} . "-$slot";
open SLOTLOCK, ">>$slotLock" or die;
if (flock(SLOTLOCK, LOCK_EX | LOCK_NB)) {
print STDERR "warning: exceeding maximum load on " . $cur->{systemType} . "\n"
if $slot >= $cur->{maxJobs};
$machine = $cur;
last LOOP;
}
close SLOTLOCK;
$slot++;
}
}
}
close MAINLOCK;
# Didn't find one? Then decline or postpone.
if (!defined $machine) {
# Postpone if we have a machine of the right type, except if the
# local system can and wants to do the build.
if ($rightType && !$canBuildLocally) {
sendReply "postpone";
exit 0;
} else {
decline;
}
}
# Yes we did, accept.
sendReply "accept";
open IN, "<&4" or die;
my $x = <IN>;
chomp $x;
#print "got $x\n";
close IN;
if ($x ne "okay") {
exit 0;
}
# Do the actual job.
my $hostName = $machine->{hostName};
print "BUILDING REMOTE: $drvPath on $hostName\n";
# Make sure that we don't get any SSH passphrase or host key popups -
# if there is any problem it should fail, not do something
# interactive.
$ENV{"DISPLAY"} = "";
$ENV{"SSH_PASSWORD_FILE="} = "";
$ENV{"SSH_ASKPASS="} = "";
my $sshOpts = "-i " . $machine->{sshKeys} . " -x";
# Hack to support Cygwin: if we login without a password, we don't
# have exactly the same rights as when we do. This causes the
# Microsoft C compiler to fail with certain flags:
#
# http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=99676
#
# So as a workaround, we pass a verbatim password. ssh tries to makes
# this very hard; the trick is to make it call SSH_ASKPASS to get the
# password. (It only calls this command when there is no controlling
# terminal, but Nix ensures that is is the case. When doing this
# manually, use setsid(1).)
if ($machine->{sshKeys} =~ /^password:/) {
my $passwordFile = $machine->{sshKeys};
$passwordFile =~ s/^password://;
$sshOpts = "ssh -x";
$ENV{"SSH_PASSWORD_FILE"} = $passwordFile;
$ENV{"SSH_ASKPASS"} = "/tmp/writepass";
open WRITEPASS, ">/tmp/writepass" or die;
print WRITEPASS "#! /bin/sh\ncat \"\$SSH_PASSWORD_FILE\"";
close WRITEPASS;
chmod 0755, "/tmp/writepass" or die;
}
my $inputs = `cat inputs`; die if ($? != 0);
$inputs =~ s/\n/ /g;
my $outputs = `cat outputs`; die if ($? != 0);
$outputs =~ s/\n/ /g;
print "COPYING INPUTS...\n";
my $maybeSign = "";
$maybeSign = "--sign" if -e "/nix/etc/nix/signing-key.sec";
system("NIX_SSHOPTS=\"$sshOpts\" nix-copy-closure $hostName $maybeSign $drvPath $inputs") == 0
or die "cannot copy inputs to $hostName: $?";
print "BUILDING...\n";
# `-tt' forces allocation of a pseudo-terminal. This is required to
# make the remote nix-store process receive a signal when the
# connection dies. Without it, the remote process might continue to
# run indefinitely (that is, until it next tries to write to
# stdout/stderr).
system("ssh -tt $sshOpts $hostName 'nix-store -rvvK $drvPath'") == 0
or die "remote build on $hostName failed: $?";
print "REMOTE BUILD DONE: $drvPath on $hostName\n";
foreach my $output (split '\n', $outputs) {
my $maybeSignRemote = "";
$maybeSignRemote = "--sign" if $UID != 0;
system("ssh $sshOpts $hostName 'nix-store --export $maybeSignRemote $output' > dump") == 0
or die "cannot copy $output from $hostName: $?";
# This doesn't work yet, since the caller has a lock on the output
# path. We should move towards lock-free invocation of build
# hooks and substitutes.
#system("nix-store --import < dump") == 0
# or die "cannot import $output: $?";
# Hack: skip the first 8 bytes (the nix-store --export next
# archive marker). The archive follows.
system("(dd bs=1 count=8 of=/dev/null && cat) < dump | nix-store --restore $output") == 0
or die "cannot restore $output: $?";
}
