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|
#! @perl@ -w -I@libexecdir@/nix
use Fcntl ':flock';
use English '-no_match_vars';
use IO::Handle;
use ssh qw/sshOpts openSSHConnection/;
# 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.
# 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_ASKPASS"} = "";
my $loadIncreased = 0;
my ($amWilling, $localSystem, $neededSystem, $drvPath, $maxSilentTime) = @ARGV;
$maxSilentTime = 0 unless defined $maxSilentTime;
sub sendReply {
my $reply = shift;
print STDERR "# $reply\n";
}
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);
# Read the list of machines.
my @machines;
open CONF, "< $conf" or die;
while (<CONF>) {
chomp;
s/\#.*$//g;
next if /^\s*$/;
/^\s*(\S+)\s+(\S+)\s+(\S+)\s+(\d+)(\s+([0-9\.]+))?\s*$/ or die;
push @machines,
{ hostName => $1
, systemTypes => [split(/,/, $2)]
, sshKeys => $3
, maxJobs => $4
, speedFactor => 1.0 * ($6 || 1)
};
}
close CONF;
# Acquire the exclusive lock on $currentLoad/main-lock.
my $mainLock = "$currentLoad/main-lock";
open MAINLOCK, ">>$mainLock" or die;
flock(MAINLOCK, LOCK_EX) or die;
sub openSlotLock {
my ($machine, $slot) = @_;
my $slotLockFn = "$currentLoad/" . (join '+', @{$machine->{systemTypes}}) . "-" . $machine->{hostName} . "-$slot";
my $slotLock = new IO::Handle;
open $slotLock, ">>$slotLockFn" or die;
return $slotLock;
}
# Find all machine that can execute this build, i.e., that support
# builds for the given platform and are not at their job limit.
my $rightType = 0;
my @available = ();
LOOP: foreach my $cur (@machines) {
if (grep { $neededSystem eq $_ } @{$cur->{systemTypes}}) {
$rightType = 1;
# We have a machine of the right type. Determine the load on
# the machine.
my $slot = 0;
my $load = 0;
my $free;
while ($slot < $cur->{maxJobs}) {
my $slotLock = openSlotLock($cur, $slot);
if (flock($slotLock, LOCK_EX | LOCK_NB)) {
$free = $slot unless defined $free;
flock($slotLock, LOCK_UN) or die;
} else {
$load++;
}
close $slotLock;
$slot++;
}
push @available, { machine => $cur, load => $load, free => $free }
if $load < $cur->{maxJobs};
}
}
if (defined $ENV{NIX_DEBUG_HOOK}) {
print STDERR "load on " . $_->{machine}->{hostName} . " = " . $_->{load} . "\n"
foreach @available;
}
# Didn't find any available machine? Then decline or postpone.
if (scalar @available == 0) {
# Postpone if we have a machine of the right type, except if the
# local system can and wants to do the build.
if ($rightType && !$canBuildLocally) {
sendReply "postpone";
exit 0;
} else {
decline;
}
}
# Prioritise the available machines as follows:
# - First by load divided by speed factor, rounded to the nearest
# integer. This causes fast machines to be preferred over slow
# machines with similar loads.
# - Then by speed factor.
# - Finally by load.
sub lf { my $x = shift; return int($x->{load} / $x->{machine}->{speedFactor} + 0.4999); }
@available = sort
{ lf($a) <=> lf($b)
|| $b->{machine}->{speedFactor} <=> $a->{machine}->{speedFactor}
|| $a->{load} <=> $b->{load}
} @available;
# Select the best available machine and lock a free slot.
my $selected = $available[0];
my $machine = $selected->{machine};
my $slotLock = openSlotLock($machine, $selected->{free});
flock($slotLock, LOCK_EX | LOCK_NB) or die;
utime undef, undef, $slotLock;
close MAINLOCK;
# Tell Nix we've accepted the build.
sendReply "accept";
if (defined $ENV{NIX_DEBUG_HOOK}) {
my $hostName = $machine->{hostName};
my $sp = $machine->{speedFactor};
print STDERR "building `$drvPath' on `$hostName' - $sp - " . $selected->{free} . "\n";
sleep 10;
exit 0;
}
my $x = <STDIN>;
chomp $x;
if ($x ne "okay") {
exit 0;
}
# Do the actual build.
my $hostName = $machine->{hostName};
print STDERR "building `$drvPath' on `$hostName'\n";
push @sshOpts, "-i", $machine->{sshKeys}, "-x";
openSSHConnection $hostName;
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\" @bindir@/nix-copy-closure $hostName $maybeSign $drvPath $inputs") == 0
or die "cannot copy inputs to $hostName: $?";
print "building...\n";
my $buildFlags = "--max-silent-time $maxSilentTime";
# `-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).
if (system("ssh $hostName @sshOpts -tt 'nix-store --realise $buildFlags $drvPath > /dev/null'") != 0) {
# If we couldn't run ssh or there was an ssh problem (indicated by
# exit code 255), then we return exit code 1; otherwise we assume
# that the builder failed, which we indicated to Nix using exit
# code 100. It's important to distinguish between the two because
# the first is a transient failure and the latter is permanent.
my $res = $? == -1 || ($? >> 8) == 255 ? 1 : 100;
print STDERR "build of `$drvPath' on `$hostName' failed with exit code $?\n";
exit $res;
}
print "build of `$drvPath' on `$hostName' succeeded\n";
foreach my $output (split '\n', $outputs) {
my $maybeSignRemote = "";
$maybeSignRemote = "--sign" if $UID != 0;
system("ssh $hostName @sshOpts 'nix-store --export $maybeSignRemote $output' | @bindir@/nix-store --import > /dev/null") == 0
or die "cannot copy $output from $hostName: $?";
}
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