X-Git-Url: http://www.git.stargrave.org/?a=blobdiff_plain;f=lib%2FPublicInbox%2FQspawn.pm;h=9aede103521b47d3684032ca29ac6ace7f0a1747;hb=cd50d183273c105a7f08b1875ba6f7a51d9f8e9a;hp=9299096a40d9d36b07e488b626ed0e1ecf3e1fed;hpb=b04e5cf1bc8969cca74ef764f2de960b1ea821a4;p=public-inbox.git

diff --git a/lib/PublicInbox/Qspawn.pm b/lib/PublicInbox/Qspawn.pm
index 9299096a..9aede103 100644
--- a/lib/PublicInbox/Qspawn.pm
+++ b/lib/PublicInbox/Qspawn.pm
@@ -1,13 +1,40 @@
-# Copyright (C) 2016 all contributors <meta@public-inbox.org>
+# Copyright (C) 2016-2019 all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# Like most Perl modules in public-inbox, this is internal and
+# NOT subject to any stability guarantees!  It is only documented
+# for other hackers.
+#
+# This is used to limit the number of processes spawned by the
+# PSGI server, so it acts like a semaphore and queues up extra
+# commands to be run if currently at the limit.  Multiple "limiters"
+# may be configured which give inboxes different channels to
+# operate in.  This can be useful to ensure smaller inboxes can
+# be cloned while cloning of large inboxes is maxed out.
+#
+# This does not depend on PublicInbox::DS or any other external
+# scheduling mechanism, you just need to call start() and finish()
+# appropriately. However, public-inbox-httpd (which uses PublicInbox::DS)
+# will be able to schedule this based on readability of stdout from
+# the spawned process.  See GitHTTPBackend.pm and SolverGit.pm for
+# usage examples.  It does not depend on any form of threading.
+#
+# This is useful for scheduling CGI execution of both long-lived
+# git-http-backend(1) process (for "git clone") as well as short-lived
+# processes such as git-apply(1).
+
 package PublicInbox::Qspawn;
 use strict;
 use warnings;
 use PublicInbox::Spawn qw(popen_rd);
-our $LIMIT = 1;
-my $running = 0;
-my @run_queue;
+require Plack::Util;
+
+my $def_limiter;
 
+# declares a command to spawn (but does not spawn it).
+# $cmd is the command to spawn
+# $env is the environ for the child process
+# $opt can include redirects and perhaps other process spawning options
 sub new ($$$;) {
 	my ($class, $cmd, $env, $opt) = @_;
 	bless { args => [ $cmd, $env, $opt ] }, $class;
@@ -16,37 +43,269 @@ sub new ($$$;) {
 sub _do_spawn {
 	my ($self, $cb) = @_;
 	my $err;
-	($self->{rpipe}, $self->{pid}) = popen_rd(@{$self->{args}});
+	my ($cmd, $env, $opts) = @{$self->{args}};
+	my %opts = %{$opts || {}};
+	my $limiter = $self->{limiter};
+	foreach my $k (PublicInbox::Spawn::RLIMITS()) {
+		if (defined(my $rlimit = $limiter->{$k})) {
+			$opts{$k} = $rlimit;
+		}
+	}
+
+	($self->{rpipe}, $self->{pid}) = popen_rd($cmd, $env, \%opts);
 	if (defined $self->{pid}) {
-		$running++;
+		$limiter->{running}++;
 	} else {
 		$self->{err} = $!;
 	}
 	$cb->($self->{rpipe});
 }
 
+sub child_err ($) {
+	my ($child_error) = @_; # typically $?
+	my $exitstatus = ($child_error >> 8) or return;
+	my $sig = $child_error & 127;
+	my $msg = "exit status=$exitstatus";
+	$msg .= " signal=$sig" if $sig;
+	$msg;
+}
+
 sub finish ($) {
 	my ($self) = @_;
+	my $limiter = $self->{limiter};
+	my $running;
 	if (delete $self->{rpipe}) {
 		my $pid = delete $self->{pid};
-		$self->{err} = $pid == waitpid($pid, 0) ? $? :
+		$self->{err} = $pid == waitpid($pid, 0) ? child_err($?) :
 				"PID:$pid still running?";
-		$running--;
+		$running = --$limiter->{running};
 	}
-	if (my $next = shift @run_queue) {
-		_do_spawn(@$next);
+
+	# limiter->{max} may change dynamically
+	if (($running || $limiter->{running}) < $limiter->{max}) {
+		if (my $next = shift @{$limiter->{run_queue}}) {
+			_do_spawn(@$next);
+		}
 	}
 	$self->{err};
 }
 
-sub start ($$) {
-	my ($self, $cb) = @_;
+sub start {
+	my ($self, $limiter, $cb) = @_;
+	$self->{limiter} = $limiter;
 
-	if ($running < $LIMIT) {
+	if ($limiter->{running} < $limiter->{max}) {
 		_do_spawn($self, $cb);
 	} else {
-		push @run_queue, [ $self, $cb ];
+		push @{$limiter->{run_queue}}, [ $self, $cb ];
+	}
+}
+
+sub _psgi_finish ($$) {
+	my ($self, $env) = @_;
+	my $err = $self->finish;
+	if ($err && !$env->{'qspawn.quiet'}) {
+		$err = join(' ', @{$self->{args}->[0]}).": $err\n";
+		$env->{'psgi.errors'}->print($err);
+	}
+}
+
+# Similar to `backtick` or "qx" ("perldoc -f qx"), it calls $qx_cb with
+# the stdout of the given command when done; but respects the given limiter
+# $env is the PSGI env.  As with ``/qx; only use this when output is small
+# and safe to slurp.
+sub psgi_qx {
+	my ($self, $env, $limiter, $qx_cb) = @_;
+	my $qx = PublicInbox::Qspawn::Qx->new;
+	my $end = sub {
+		_psgi_finish($self, $env);
+		eval { $qx_cb->($qx) };
+		$qx = undef;
+	};
+	my $rpipe;
+	my $async = $env->{'pi-httpd.async'};
+	my $cb = sub {
+		my $r = sysread($rpipe, my $buf, 8192);
+		if ($async) {
+			$async->async_pass($env->{'psgix.io'}, $qx, \$buf);
+		} elsif (defined $r) {
+			$r ? $qx->write($buf) : $end->();
+		} else {
+			return if $!{EAGAIN} || $!{EINTR}; # loop again
+			$end->();
+		}
+	};
+	$limiter ||= $def_limiter ||= PublicInbox::Qspawn::Limiter->new(32);
+	$self->start($limiter, sub { # may run later, much later...
+		($rpipe) = @_;
+		if ($async) {
+		# PublicInbox::HTTPD::Async->new($rpipe, $cb, $end)
+			$async = $async->($rpipe, $cb, $end);
+		} else { # generic PSGI
+			$cb->() while $qx;
+		}
+	});
+}
+
+# create a filter for "push"-based streaming PSGI writes used by HTTPD::Async
+sub filter_fh ($$) {
+	my ($fh, $filter) = @_;
+	Plack::Util::inline_object(
+		close => sub {
+			$fh->write($filter->(undef));
+			$fh->close;
+		},
+		write => sub {
+			$fh->write($filter->($_[0]));
+		});
+}
+
+# Used for streaming the stdout of one process as a PSGI response.
+#
+# $env is the PSGI env.
+# optional keys in $env:
+#   $env->{'qspawn.wcb'} - the write callback from the PSGI server
+#                          optional, use this if you've already
+#                          captured it elsewhere.  If not given,
+#                          psgi_return will return an anonymous
+#                          sub for the PSGI server to call
+#
+#   $env->{'qspawn.filter'} - filter callback, receives a string as input,
+#                             undef on EOF
+#
+# $limiter - the Limiter object to use (uses the def_limiter if not given)
+#
+# $parse_hdr - Initial read function; often for parsing CGI header output.
+#              It will be given the return value of sysread from the pipe
+#              and a string ref of the current buffer.  Returns an arrayref
+#              for PSGI responses.  2-element arrays in PSGI mean the
+#              body will be streamed, later, via writes (push-based) to
+#              psgix.io.  3-element arrays means the body is available
+#              immediately (or streamed via ->getline (pull-based)).
+sub psgi_return {
+	my ($self, $env, $limiter, $parse_hdr) = @_;
+	my ($fh, $rpipe);
+	my $end = sub {
+		_psgi_finish($self, $env);
+		$fh->close if $fh; # async-only
+	};
+
+	my $buf = '';
+	my $rd_hdr = sub {
+		my $r = sysread($rpipe, $buf, 1024, length($buf));
+		return if !defined($r) && ($!{EINTR} || $!{EAGAIN});
+		$parse_hdr->($r, \$buf);
+	};
+
+	my $wcb = delete $env->{'qspawn.wcb'};
+	my $async = $env->{'pi-httpd.async'};
+
+	my $cb = sub {
+		my $r = $rd_hdr->() or return;
+		$rd_hdr = undef;
+		my $filter = delete $env->{'qspawn.filter'};
+		if (scalar(@$r) == 3) { # error
+			if ($async) {
+				$async->close; # calls rpipe->close and $end
+			} else {
+				$rpipe->close;
+				$end->();
+			}
+			$wcb->($r);
+		} elsif ($async) {
+			$fh = $wcb->($r); # scalar @$r == 2
+			$fh = filter_fh($fh, $filter) if $filter;
+			$async->async_pass($env->{'psgix.io'}, $fh, \$buf);
+		} else { # for synchronous PSGI servers
+			require PublicInbox::GetlineBody;
+			$r->[2] = PublicInbox::GetlineBody->new($rpipe, $end,
+								$buf, $filter);
+			$wcb->($r);
+		}
+	};
+	$limiter ||= $def_limiter ||= PublicInbox::Qspawn::Limiter->new(32);
+	my $start_cb = sub { # may run later, much later...
+		($rpipe) = @_;
+		if ($async) {
+			# PublicInbox::HTTPD::Async->new($rpipe, $cb, $end)
+			$async = $async->($rpipe, $cb, $end);
+		} else { # generic PSGI
+			$cb->() while $rd_hdr;
+		}
+	};
+
+	# the caller already captured the PSGI write callback from
+	# the PSGI server, so we can call ->start, here:
+	return $self->start($limiter, $start_cb) if $wcb;
+
+	# the caller will return this sub to the PSGI server, so
+	# it can set the response callback (that is, for PublicInbox::HTTP,
+	# the chunked_wcb or identity_wcb callback), but other HTTP servers
+	# are supported:
+	sub {
+		($wcb) = @_;
+		$self->start($limiter, $start_cb);
+	};
+}
+
+package PublicInbox::Qspawn::Limiter;
+use strict;
+use warnings;
+
+sub new {
+	my ($class, $max) = @_;
+	bless {
+		# 32 is same as the git-daemon connection limit
+		max => $max || 32,
+		running => 0,
+		run_queue => [],
+		# RLIMIT_CPU => undef,
+		# RLIMIT_DATA => undef,
+		# RLIMIT_CORE => undef,
+	}, $class;
+}
+
+sub setup_rlimit {
+	my ($self, $name, $config) = @_;
+	foreach my $rlim (PublicInbox::Spawn::RLIMITS()) {
+		my $k = lc($rlim);
+		$k =~ tr/_//d;
+		$k = "publicinboxlimiter.$name.$k";
+		defined(my $v = $config->{$k}) or next;
+		my @rlimit = split(/\s*,\s*/, $v);
+		if (scalar(@rlimit) == 1) {
+			push @rlimit, $rlimit[0];
+		} elsif (scalar(@rlimit) != 2) {
+			warn "could not parse $k: $v\n";
+		}
+		eval { require BSD::Resource };
+		if ($@) {
+			warn "BSD::Resource missing for $rlim";
+			next;
+		}
+		foreach my $i (0..$#rlimit) {
+			next if $rlimit[$i] ne 'INFINITY';
+			$rlimit[$i] = BSD::Resource::RLIM_INFINITY();
+		}
+		$self->{$rlim} = \@rlimit;
 	}
 }
 
+# captures everything into a buffer and executes a callback when done
+package PublicInbox::Qspawn::Qx;
+use strict;
+use warnings;
+
+sub new {
+	my ($class) = @_;
+	my $buf = '';
+	bless \$buf, $class;
+}
+
+# called by PublicInbox::HTTPD::Async ($fh->write)
+sub write {
+	${$_[0]} .= $_[1];
+	undef;
+}
+
 1;