-# Copyright (C) 2016 all contributors <meta@public-inbox.org>
+# Copyright (C) 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 the PublicInbox::DS::event_loop 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 v5.12;
use PublicInbox::Spawn qw(popen_rd);
-our $LIMIT = 1;
-my $running = 0;
-my @run_queue;
+use PublicInbox::GzipFilter;
+use Scalar::Util qw(blessed);
+
+# n.b.: we get EAGAIN with public-inbox-httpd, and EINTR on other PSGI servers
+use Errno qw(EAGAIN EINTR);
+
+my $def_limiter;
-sub new ($$$;) {
- my ($class, $cmd, $env, $opt) = @_;
- bless { args => [ $cmd, $env, $opt ] }, $class;
+# declares a command to spawn (but does not spawn it).
+# $cmd is the command to spawn
+# $cmd_env is the environ for the child process (not PSGI env)
+# $opt can include redirects and perhaps other process spawning options
+# {qsp_err} is an optional error buffer callers may access themselves
+sub new {
+ my ($class, $cmd, $cmd_env, $opt) = @_;
+ bless { args => [ $cmd, $cmd_env, $opt ] }, $class;
}
sub _do_spawn {
- my ($self, $cb) = @_;
+ my ($self, $start_cb, $limiter) = @_;
my $err;
- ($self->{rpipe}, $self->{pid}) = popen_rd(@{$self->{args}});
- if (defined $self->{pid}) {
- $running++;
- } else {
- $self->{err} = $!;
+ my ($cmd, $cmd_env, $opt) = @{delete $self->{args}};
+ my %o = %{$opt || {}};
+ $self->{limiter} = $limiter;
+ foreach my $k (@PublicInbox::Spawn::RLIMITS) {
+ if (defined(my $rlimit = $limiter->{$k})) {
+ $o{$k} = $rlimit;
+ }
}
- $cb->($self->{rpipe});
+ $self->{cmd} = $cmd;
+ $self->{-quiet} = 1 if $o{quiet};
+ $o{cb_arg} = [ \&waitpid_err, $self ];
+ eval {
+ # popen_rd may die on EMFILE, ENFILE
+ $self->{rpipe} = popen_rd($cmd, $cmd_env, \%o) // die "E: $!";
+ $limiter->{running}++;
+ $start_cb->($self); # EPOLL_CTL_ADD may ENOSPC/ENOMEM
+ };
+ finish($self, $@) if $@;
}
-sub finish ($) {
+sub finalize ($) {
my ($self) = @_;
- if (delete $self->{rpipe}) {
- my $pid = delete $self->{pid};
- $self->{err} = $pid == waitpid($pid, 0) ? $? :
- "PID:$pid still running?";
- $running--;
+
+ # process is done, spawn whatever's in the queue
+ my $limiter = delete $self->{limiter} or return;
+ my $running = --$limiter->{running};
+
+ if ($running < $limiter->{max}) {
+ if (my $next = shift(@{$limiter->{run_queue}})) {
+ _do_spawn(@$next, $limiter);
+ }
}
- if (my $next = shift @run_queue) {
- _do_spawn(@$next);
+ if (my $err = $self->{_err}) { # set by finish or waitpid_err
+ utf8::decode($err);
+ if (my $dst = $self->{qsp_err}) {
+ $$dst .= $$dst ? " $err" : "; $err";
+ }
+ warn "@{$self->{cmd}}: $err\n" if !$self->{-quiet};
+ }
+
+ my ($env, $qx_cb, $qx_arg, $qx_buf) =
+ delete @$self{qw(psgi_env qx_cb qx_arg qx_buf)};
+ if ($qx_cb) {
+ eval { $qx_cb->($qx_buf, $qx_arg) };
+ return unless $@;
+ warn "E: $@"; # hope qspawn.wcb can handle it
+ }
+ return if $self->{passed}; # another command chained it
+ if (my $wcb = delete $env->{'qspawn.wcb'}) {
+ # have we started writing, yet?
+ my $code = delete $env->{'qspawn.fallback'} // 500;
+ require PublicInbox::WwwStatic;
+ $wcb->(PublicInbox::WwwStatic::r($code));
+ }
+}
+
+sub DESTROY { finalize($_[0]) } # ->finalize is idempotent
+
+sub waitpid_err { # callback for awaitpid
+ my (undef, $self) = @_; # $_[0]: pid
+ $self->{_err} = ''; # for defined check in ->finish
+ if ($?) {
+ my $status = $? >> 8;
+ my $sig = $? & 127;
+ $self->{_err} .= "exit status=$status";
+ $self->{_err} .= " signal=$sig" if $sig;
}
- $self->{err};
+ finalize($self) if !$self->{rpipe};
}
-sub start ($$) {
- my ($self, $cb) = @_;
+sub finish ($;$) {
+ my ($self, $err) = @_;
+ $self->{_err} //= $err; # only for $@
- if ($running < $LIMIT) {
- _do_spawn($self, $cb);
+ # we can safely finalize if pipe was closed before, or if
+ # {_err} is defined by waitpid_err. Deleting {rpipe} will
+ # trigger PublicInbox::ProcessPipe::DESTROY -> waitpid_err,
+ # but it may not fire right away if inside the event loop.
+ my $closed_before = !delete($self->{rpipe});
+ finalize($self) if $closed_before || defined($self->{_err});
+}
+
+sub start ($$$) {
+ my ($self, $limiter, $start_cb) = @_;
+ if ($limiter->{running} < $limiter->{max}) {
+ _do_spawn($self, $start_cb, $limiter);
} else {
- push @run_queue, [ $self, $cb ];
+ push @{$limiter->{run_queue}}, [ $self, $start_cb ];
+ }
+}
+
+sub psgi_qx_init_cb { # this may be PublicInbox::HTTPD::Async {cb}
+ my ($self) = @_;
+ my ($r, $buf);
+reread:
+ $r = sysread($self->{rpipe}, $buf, 65536);
+ if (!defined($r)) {
+ return if $! == EAGAIN; # try again when notified
+ goto reread if $! == EINTR;
+ event_step($self, $!);
+ } elsif (my $as = delete $self->{async}) { # PublicInbox::HTTPD::Async
+ $as->async_pass($self->{psgi_env}->{'psgix.io'},
+ $self->{qx_fh}, \$buf);
+ } elsif ($r) { # generic PSGI:
+ print { $self->{qx_fh} } $buf;
+ } else { # EOF
+ event_step($self, undef);
+ }
+}
+
+sub psgi_qx_start {
+ my ($self) = @_;
+ if (my $async = $self->{psgi_env}->{'pi-httpd.async'}) {
+ # PublicInbox::HTTPD::Async->new(rpipe, $cb, cb_arg, $end_obj)
+ $self->{async} = $async->($self->{rpipe},
+ \&psgi_qx_init_cb, $self, $self);
+ # init_cb will call ->async_pass or ->close
+ } else { # generic PSGI
+ psgi_qx_init_cb($self) while $self->{qx_fh};
+ }
+}
+
+# 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, $qx_arg) = @_;
+ $self->{psgi_env} = $env;
+ my $qx_buf = '';
+ open(my $qx_fh, '+>', \$qx_buf) or die; # PerlIO::scalar
+ $self->{qx_cb} = $qx_cb;
+ $self->{qx_arg} = $qx_arg;
+ $self->{qx_fh} = $qx_fh;
+ $self->{qx_buf} = \$qx_buf;
+ $limiter ||= $def_limiter ||= PublicInbox::Qspawn::Limiter->new(32);
+ start($self, $limiter, \&psgi_qx_start);
+}
+
+# this is called on pipe EOF to reap the process, may be called
+# via PublicInbox::DS event loop OR via GetlineBody for generic
+# PSGI servers.
+sub event_step {
+ my ($self, $err) = @_; # $err: $!
+ warn "psgi_{return,qx} $err" if defined($err);
+ finish($self);
+ my ($fh, $qx_fh) = delete(@$self{qw(qfh qx_fh)});
+ $fh->close if $fh; # async-only (psgi_return)
+}
+
+sub rd_hdr ($) {
+ my ($self) = @_;
+ # typically used for reading CGI headers
+ # We also need to check EINTR for generic PSGI servers.
+ my $ret;
+ my $total_rd = 0;
+ my $hdr_buf = $self->{hdr_buf};
+ my ($ph_cb, $ph_arg) = @{$self->{parse_hdr}};
+ until (defined($ret)) {
+ my $r = sysread($self->{rpipe}, $$hdr_buf, 4096,
+ length($$hdr_buf));
+ if (defined($r)) {
+ $total_rd += $r;
+ eval { $ret = $ph_cb->($total_rd, $hdr_buf, $ph_arg) };
+ if ($@) {
+ warn "parse_hdr: $@";
+ $ret = [ 500, [], [ "Internal error\n" ] ];
+ } elsif (!defined($ret) && !$r) {
+ warn <<EOM;
+EOF parsing headers from @{$self->{cmd}} ($self->{psgi_env}->{REQUEST_URI})
+EOM
+ $ret = [ 500, [], [ "Internal error\n" ] ];
+ }
+ } else {
+ # caller should notify us when it's ready:
+ return if $! == EAGAIN;
+ next if $! == EINTR; # immediate retry
+ warn "error reading header: $!";
+ $ret = [ 500, [], [ "Internal error\n" ] ];
+ }
+ }
+ delete $self->{parse_hdr}; # done parsing headers
+ $ret;
+}
+
+sub psgi_return_init_cb { # this may be PublicInbox::HTTPD::Async {cb}
+ my ($self) = @_;
+ my $r = rd_hdr($self) or return;
+ my $env = $self->{psgi_env};
+ my $filter;
+
+ # this is for RepoAtom since that can fire after parse_cgi_headers
+ if (ref($r) eq 'ARRAY' && blessed($r->[2]) && $r->[2]->can('attach')) {
+ $filter = pop @$r;
+ }
+ $filter //= delete($env->{'qspawn.filter'}) // (ref($r) eq 'ARRAY' ?
+ PublicInbox::GzipFilter::qsp_maybe($r->[1], $env) : undef);
+
+ my $wcb = delete $env->{'qspawn.wcb'};
+ my $async = delete $self->{async}; # PublicInbox::HTTPD::Async
+ if (ref($r) ne 'ARRAY' || scalar(@$r) == 3) { # error
+ if ($async) { # calls rpipe->close && ->event_step
+ $async->close; # PublicInbox::HTTPD::Async::close
+ } else { # generic PSGI, use PublicInbox::ProcessPipe::CLOSE
+ delete($self->{rpipe})->close;
+ event_step($self);
+ }
+ if (ref($r) eq 'ARRAY') { # error
+ $wcb->($r)
+ } elsif (ref($r) eq 'CODE') { # chain another command
+ $r->($wcb);
+ $self->{passed} = 1;
+ }
+ # else do nothing
+ } elsif ($async) {
+ # done reading headers, handoff to read body
+ my $fh = $wcb->($r); # scalar @$r == 2
+ $fh = $filter->attach($fh) if $filter;
+ $self->{qfh} = $fh;
+ $async->async_pass($env->{'psgix.io'}, $fh,
+ delete($self->{hdr_buf}));
+ } else { # for synchronous PSGI servers
+ require PublicInbox::GetlineBody;
+ my $buf = delete $self->{hdr_buf};
+ $r->[2] = PublicInbox::GetlineBody->new($self->{rpipe},
+ \&event_step, $self, $$buf, $filter);
+ $wcb->($r);
+ }
+}
+
+sub psgi_return_start { # may run later, much later...
+ my ($self) = @_;
+ if (my $cb = $self->{psgi_env}->{'pi-httpd.async'}) {
+ # PublicInbox::HTTPD::Async->new(rpipe, $cb, $cb_arg, $end_obj)
+ $self->{async} = $cb->($self->{rpipe},
+ \&psgi_return_init_cb, $self, $self);
+ } else { # generic PSGI
+ psgi_return_init_cb($self) while $self->{parse_hdr};
+ }
+}
+
+# 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 object, responds to ->attach for
+# pi-httpd.async and ->translate for generic
+# PSGI servers
+#
+# $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, $hdr_arg) = @_;
+ $self->{psgi_env} = $env;
+ $self->{hdr_buf} = \(my $hdr_buf = '');
+ $self->{parse_hdr} = [ $parse_hdr, $hdr_arg ];
+ $limiter ||= $def_limiter ||= PublicInbox::Qspawn::Limiter->new(32);
+
+ # the caller already captured the PSGI write callback from
+ # the PSGI server, so we can call ->start, here:
+ $env->{'qspawn.wcb'} and
+ return start($self, $limiter, \&psgi_return_start);
+
+ # 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 {
+ $env->{'qspawn.wcb'} = $_[0];
+ start($self, $limiter, \&psgi_return_start);
+ }
+}
+
+package PublicInbox::Qspawn::Limiter;
+use v5.12;
+
+sub new {
+ my ($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, $cfg) = @_;
+ foreach my $rlim (@PublicInbox::Spawn::RLIMITS) {
+ my $k = lc($rlim);
+ $k =~ tr/_//d;
+ $k = "publicinboxlimiter.$name.$k";
+ defined(my $v = $cfg->{$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;
}
}