-# 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 ($$$;) {
my ($class, $cmd, $env, $opt) = @_;
bless { args => [ $cmd, $env, $opt ] }, $class;
sub _do_spawn {
my ($self, $cb) = @_;
my $err;
- ($self->{rpipe}, $self->{pid}) = popen_rd(@{$self->{args}});
+ my ($cmd, $env, $opts) = @{$self->{args}};
+ my %opts = %{$opts || {}};
+ my $limiter = $self->{limiter};
+ foreach my $k (PublicInbox::Spawn::RLIMITS()) {
+ if (defined(my $rlimit = $limiter->{$k})) {
+ $opts{$k} = $rlimit;
+ }
+ }
+
+ ($self->{rpipe}, $self->{pid}) = popen_rd($cmd, $env, \%opts);
if (defined $self->{pid}) {
- $running++;
+ $limiter->{running}++;
} else {
$self->{err} = $!;
}
$cb->($self->{rpipe});
}
+sub child_err ($) {
+ my ($child_error) = @_; # typically $?
+ my $exitstatus = ($child_error >> 8) or return;
+ my $sig = $child_error & 127;
+ my $msg = "exit status=$exitstatus";
+ $msg .= " signal=$sig" if $sig;
+ $msg;
+}
+
sub finish ($) {
my ($self) = @_;
+ my $limiter = $self->{limiter};
+ my $running;
if (delete $self->{rpipe}) {
my $pid = delete $self->{pid};
- $self->{err} = $pid == waitpid($pid, 0) ? $? :
+ $self->{err} = $pid == waitpid($pid, 0) ? child_err($?) :
"PID:$pid still running?";
- $running--;
+ $running = --$limiter->{running};
}
- if (my $next = shift @run_queue) {
- _do_spawn(@$next);
+
+ # limiter->{max} may change dynamically
+ if (($running || $limiter->{running}) < $limiter->{max}) {
+ if (my $next = shift @{$limiter->{run_queue}}) {
+ _do_spawn(@$next);
+ }
}
$self->{err};
}
-sub start ($$) {
- 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;