766f708418
it requires a certain feature on the build machine, e.g.
requiredSystemFeatures = [ "kvm" ];
We need this in Hydra to make sure that builds that require KVM
support are forwarded to machines that have KVM support. Probably
this should also be enforced for local builds.
263 lines
8.7 KiB
Perl
Executable file
263 lines
8.7 KiB
Perl
Executable file
#! @perl@ -w -I@libexecdir@/nix
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use Fcntl ':flock';
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use English '-no_match_vars';
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use IO::Handle;
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use ssh qw/sshOpts openSSHConnection/;
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# General operation:
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#
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# Try to find a free machine of type $neededSystem. We do this as
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# follows:
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# - We acquire an exclusive lock on $currentLoad/main-lock.
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# - For each machine $machine of type $neededSystem and for each $slot
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# less than the maximum load for that machine, we try to get an
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# exclusive lock on $currentLoad/$machine-$slot (without blocking).
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# If we get such a lock, we send "accept" to the caller. Otherwise,
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# we send "postpone" and exit.
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# - We release the exclusive lock on $currentLoad/main-lock.
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# - We perform the build on $neededSystem.
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# - We release the exclusive lock on $currentLoad/$machine-$slot.
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#
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# The nice thing about this scheme is that if we die prematurely, the
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# locks are released automatically.
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# Make sure that we don't get any SSH passphrase or host key popups -
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# if there is any problem it should fail, not do something
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# interactive.
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$ENV{"DISPLAY"} = "";
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$ENV{"SSH_ASKPASS"} = "";
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sub sendReply {
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my $reply = shift;
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print STDERR "# $reply\n";
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}
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sub all { $_ || return 0 for @_; 1 }
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# Initialisation.
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my $loadIncreased = 0;
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my ($localSystem, $maxSilentTime) = @ARGV;
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$maxSilentTime = 0 unless defined $maxSilentTime;
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my $currentLoad = $ENV{"NIX_CURRENT_LOAD"};
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my $conf = $ENV{"NIX_REMOTE_SYSTEMS"};
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sub openSlotLock {
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my ($machine, $slot) = @_;
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my $slotLockFn = "$currentLoad/" . (join '+', @{$machine->{systemTypes}}) . "-" . $machine->{hostName} . "-$slot";
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my $slotLock = new IO::Handle;
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open $slotLock, ">>$slotLockFn" or die;
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return $slotLock;
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}
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# Read the list of machines.
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my @machines;
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if (defined $conf && -e $conf) {
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open CONF, "< $conf" or die;
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while (<CONF>) {
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chomp;
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s/\#.*$//g;
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next if /^\s*$/;
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my @tokens = split /\s/, $_;
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push @machines,
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{ hostName => $tokens[0]
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, systemTypes => [ split(/,/, $tokens[1]) ]
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, sshKeys => $tokens[2]
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, maxJobs => int($tokens[3])
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, speedFactor => 1.0 * (defined $tokens[4] ? int($tokens[4]) : 1)
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, features => [ split(/,/, $tokens[5] || "") ]
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, enabled => 1
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};
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}
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close CONF;
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}
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# Wait for the calling process to ask us whether we can build some derivation.
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my ($drvPath, $hostName, $slotLock);
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REQ: while (1) {
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$_ = <STDIN> || exit 0;
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my ($amWilling, $neededSystem);
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($amWilling, $neededSystem, $drvPath, $requiredFeatures) = split;
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my @requiredFeatures = split /,/, $requiredFeatures;
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my $canBuildLocally = $amWilling && ($localSystem eq $neededSystem);
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if (!defined $currentLoad) {
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sendReply "decline";
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next;
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}
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# Acquire the exclusive lock on $currentLoad/main-lock.
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mkdir $currentLoad, 0777 or die unless -d $currentLoad;
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my $mainLock = "$currentLoad/main-lock";
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open MAINLOCK, ">>$mainLock" or die;
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flock(MAINLOCK, LOCK_EX) or die;
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while (1) {
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# Find all machine that can execute this build, i.e., that
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# support builds for the given platform and features, and are
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# not at their job limit.
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my $rightType = 0;
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my @available = ();
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LOOP: foreach my $cur (@machines) {
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if ($cur->{enabled}
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&& (grep { $neededSystem eq $_ } @{$cur->{systemTypes}})
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&& all(map { my $f = $_; 0 != grep { $f eq $_ } @{$cur->{features}} } @requiredFeatures))
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{
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$rightType = 1;
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# We have a machine of the right type. Determine the load on
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# the machine.
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my $slot = 0;
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my $load = 0;
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my $free;
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while ($slot < $cur->{maxJobs}) {
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my $slotLock = openSlotLock($cur, $slot);
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if (flock($slotLock, LOCK_EX | LOCK_NB)) {
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$free = $slot unless defined $free;
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flock($slotLock, LOCK_UN) or die;
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} else {
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$load++;
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}
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close $slotLock;
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$slot++;
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}
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push @available, { machine => $cur, load => $load, free => $free }
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if $load < $cur->{maxJobs};
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}
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}
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if (defined $ENV{NIX_DEBUG_HOOK}) {
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print STDERR "load on " . $_->{machine}->{hostName} . " = " . $_->{load} . "\n"
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foreach @available;
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}
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# Didn't find any available machine? Then decline or postpone.
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if (scalar @available == 0) {
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# Postpone if we have a machine of the right type, except
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# if the local system can and wants to do the build.
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if ($rightType && !$canBuildLocally) {
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sendReply "postpone";
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} else {
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sendReply "decline";
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}
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close MAINLOCK;
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next REQ;
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}
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# Prioritise the available machines as follows:
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# - First by load divided by speed factor, rounded to the nearest
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# integer. This causes fast machines to be preferred over slow
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# machines with similar loads.
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# - Then by speed factor.
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# - Finally by load.
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sub lf { my $x = shift; return int($x->{load} / $x->{machine}->{speedFactor} + 0.4999); }
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@available = sort
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{ lf($a) <=> lf($b)
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|| $b->{machine}->{speedFactor} <=> $a->{machine}->{speedFactor}
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|| $a->{load} <=> $b->{load}
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} @available;
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# Select the best available machine and lock a free slot.
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my $selected = $available[0];
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my $machine = $selected->{machine};
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$slotLock = openSlotLock($machine, $selected->{free});
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flock($slotLock, LOCK_EX | LOCK_NB) or die;
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utime undef, undef, $slotLock;
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close MAINLOCK;
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# Connect to the selected machine.
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@sshOpts = ("-i", $machine->{sshKeys}, "-x");
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$hostName = $machine->{hostName};
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last REQ if openSSHConnection $hostName;
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warn "unable to open SSH connection to $hostName, trying other available machines...\n";
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$machine->{enabled} = 0;
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}
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}
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# Tell Nix we've accepted the build.
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print STDERR "building `$drvPath' on `$hostName'\n";
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sendReply "accept";
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my @inputs = split /\s/, readline(STDIN);
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my @outputs = split /\s/, readline(STDIN);
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my $maybeSign = "";
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$maybeSign = "--sign" if -e "/nix/etc/nix/signing-key.sec";
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# Register the derivation as a temporary GC root. Note that $PPID is
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# the PID of the remote SSH process, which, due to the use of a
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# persistant SSH connection, should be the same across all remote
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# command invocations for this session.
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my $rootsDir = "@localstatedir@/nix/gcroots/tmp";
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system("ssh $hostName @sshOpts 'mkdir -m 1777 -p $rootsDir; ln -sfn $drvPath $rootsDir/\$PPID.drv'");
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sub removeRoots {
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system("ssh $hostName @sshOpts 'rm -f $rootsDir/\$PPID.drv $rootsDir/\$PPID.out'");
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}
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# Copy the derivation and its dependencies to the build machine.
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system("NIX_SSHOPTS=\"@sshOpts\" @bindir@/nix-copy-closure $hostName $maybeSign $drvPath @inputs") == 0
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or die "cannot copy inputs to $hostName: $?";
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# Perform the build.
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my $buildFlags = "--max-silent-time $maxSilentTime --fallback --add-root $rootsDir/\$PPID.out";
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# `-tt' forces allocation of a pseudo-terminal. This is required to
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# make the remote nix-store process receive a signal when the
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# connection dies. Without it, the remote process might continue to
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# run indefinitely (that is, until it next tries to write to
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# stdout/stderr).
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if (system("ssh $hostName @sshOpts -tt 'nix-store -r $drvPath $buildFlags > /dev/null'") != 0) {
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# If we couldn't run ssh or there was an ssh problem (indicated by
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# exit code 255), then we return exit code 1; otherwise we assume
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# that the builder failed, which we indicate to Nix using exit
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# code 100. It's important to distinguish between the two because
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# the first is a transient failure and the latter is permanent.
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my $res = $? == -1 || ($? >> 8) == 255 ? 1 : 100;
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print STDERR "build of `$drvPath' on `$hostName' failed with exit code $?\n";
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removeRoots;
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exit $res;
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}
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#print "build of `$drvPath' on `$hostName' succeeded\n";
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# Copy the output from the build machine.
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foreach my $output (@outputs) {
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my $maybeSignRemote = "";
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$maybeSignRemote = "--sign" if $UID != 0;
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system("ssh $hostName @sshOpts 'nix-store --export $maybeSignRemote $output'" .
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"| NIX_HELD_LOCKS=$output @bindir@/nix-store --import > /dev/null") == 0
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or die "cannot copy $output from $hostName: $?";
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}
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# Get rid of the temporary GC roots.
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removeRoots;
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