mboxgz: do asynchronous git blob retrievals

This lets the -httpd worker process make better use of time
instead of waiting for git-cat-file to respond.  With 4 jobs in
the new test case against a clone of
<https://public-inbox.org/meta/>, a speedup of 10-12% is shown.
Even a single job shows a 2-5% improvement on an SSD.

1 files changed, 99 insertions, 0 deletions

diff --git a/xt/httpd-async-stream.t b/xt/httpd-async-stream.t
new file mode 100644
index 00000000..29bcb612
--- /dev/null
+++ b/xt/httpd-async-stream.t
@@ -0,0 +1,99 @@
+#!perl -w
+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+# Expensive test to validate compression and TLS.
+use strict;
+use Test::More;
+use PublicInbox::TestCommon;
+use PublicInbox::DS qw(now);
+use PublicInbox::Spawn qw(which popen_rd);
+use Digest::MD5;
+use POSIX qw(_exit);
+my $inboxdir = $ENV{GIANT_INBOX_DIR};
+plan skip_all => "GIANT_INBOX_DIR not defined for $0" unless $inboxdir;
+my $curl = which('curl') or plan skip_all => "curl(1) missing for $0";
+my ($tmpdir, $for_destroy) = tmpdir();
+require_mods(qw(DBD::SQLite));
+my $JOBS = $ENV{TEST_JOBS} // 4;
+diag "TEST_JOBS=$JOBS";
+
+my $make_local_server = sub {
+        my $pi_config = "$tmpdir/config";
+        open my $fh, '>', $pi_config or die "open($pi_config): $!";
+        print $fh <<"" or die "print $pi_config: $!";
+[publicinbox "test"]
+inboxdir = $inboxdir
+address = test\@example.com
+
+        close $fh or die "close($pi_config): $!";
+        my ($out, $err) = ("$tmpdir/out", "$tmpdir/err");
+        for ($out, $err) {
+                open my $fh, '>', $_ or die "truncate: $!";
+        }
+        my $http = tcp_server();
+        my $rdr = { 3 => $http };
+
+        # not using multiple workers, here, since we want to increase
+        # the chance of tripping concurrency bugs within PublicInbox/HTTP*.pm
+        my $cmd = [ '-httpd', "--stdout=$out", "--stderr=$err", '-W0' ];
+        my $host_port = $http->sockhost.':'.$http->sockport;
+        push @$cmd, "-lhttp://$host_port";
+        my $url = "$host_port/test/all.mbox.gz";
+        print STDERR "# CMD ". join(' ', @$cmd). "\n";
+        my $env = { PI_CONFIG => $pi_config };
+        (start_script($cmd, $env, $rdr), $url);
+};
+
+my ($td, $url) = $make_local_server->();
+
+my $do_get_all = sub {
+        my ($job) = @_;
+        local $SIG{__DIE__} = sub { print STDERR $job, ': ', @_; _exit(1) };
+        my $dig = Digest::MD5->new;
+        my ($buf, $nr);
+        my $bytes = 0;
+        my $t0 = now();
+        my ($rd, $pid) = popen_rd([$curl, qw(-HHost:example.com -sSf), $url]);
+        while (1) {
+                $nr = sysread($rd, $buf, 65536);
+                last if !$nr;
+                $dig->add($buf);
+                $bytes += $nr;
+        }
+        my $res = $dig->hexdigest;
+        my $elapsed = sprintf('%0.3f', now() - $t0);
+        close $rd or die "close curl failed: $!\n";
+        waitpid($pid, 0) == $pid or die "waitpid failed: $!\n";
+        $? == 0 or die "curl failed: $?\n";
+        print STDERR "# $job $$ ($?) $res (${elapsed}s) $bytes bytes\n";
+        $res;
+};
+
+my (%pids, %res);
+for my $job (1..$JOBS) {
+        pipe(my ($r, $w)) or die;
+        my $pid = fork;
+        if ($pid == 0) {
+                close $r or die;
+                my $res = $do_get_all->($job);
+                print $w $res or die;
+                close $w or die;
+                _exit(0);
+        }
+        close $w or die;
+        $pids{$pid} = [ $job, $r ];
+}
+
+while (scalar keys %pids) {
+        my $pid = waitpid(-1, 0) or next;
+        my $child = delete $pids{$pid} or next;
+        my ($job, $rpipe) = @$child;
+        is($?, 0, "$job done");
+        my $sum = do { local $/; <$rpipe> };
+        push @{$res{$sum}}, $job;
+}
+is(scalar keys %res, 1, 'all got the same result');
+$td->kill;
+$td->join;
+is($?, 0, 'no error on -httpd exit');
+done_testing;