[PATCH 1/2] tmpfile: give temporary files meaningful names

[Eric Wong <e@80x24.org>]

Although we always unlink temporary files, give them a
meaningful name so that we can we can still make sense
of the pre-unlink name when using lsof(8) or similar
tools on Linux.
---
 MANIFEST                          |  1 +
 lib/PublicInbox/Git.pm            |  4 +++-
 lib/PublicInbox/GitHTTPBackend.pm |  4 +++-
 lib/PublicInbox/HTTP.pm           | 10 ++++----
 lib/PublicInbox/SolverGit.pm      |  3 ++-
 lib/PublicInbox/Tmpfile.pm        | 38 +++++++++++++++++++++++++++++++
 lib/PublicInbox/ViewVCS.pm        |  3 ++-
 7 files changed, 55 insertions(+), 8 deletions(-)
 create mode 100644 lib/PublicInbox/Tmpfile.pm

diff --git a/MANIFEST b/MANIFEST
index 24280351..777367d0 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -135,6 +135,7 @@ lib/PublicInbox/Spawn.pm
 lib/PublicInbox/SpawnPP.pm
 lib/PublicInbox/Syscall.pm
 lib/PublicInbox/TLS.pm
+lib/PublicInbox/Tmpfile.pm
 lib/PublicInbox/Unsubscribe.pm
 lib/PublicInbox/UserContent.pm
 lib/PublicInbox/V2Writable.pm
diff --git a/lib/PublicInbox/Git.pm b/lib/PublicInbox/Git.pm
index d048051e..ff3838b3 100644
--- a/lib/PublicInbox/Git.pm
+++ b/lib/PublicInbox/Git.pm
@@ -12,6 +12,7 @@ use warnings;
 use POSIX qw(dup2);
 require IO::Handle;
 use PublicInbox::Spawn qw(spawn popen_rd);
+use PublicInbox::Tmpfile;
 use base qw(Exporter);
 our @EXPORT_OK = qw(git_unquote git_quote);
 
@@ -110,7 +111,8 @@ sub _bidi_pipe {
 			qw(-c core.abbrev=40 cat-file), $batch);
 	my $redir = { 0 => fileno($out_r), 1 => fileno($in_w) };
 	if ($err) {
-		open(my $fh, '+>', undef) or fail($self, "open.err failed: $!");
+		my $id = "git.$self->{git_dir}$batch.err";
+		my $fh = tmpfile($id) or fail($self, "tmpfile($id): $!");
 		$self->{$err} = $fh;
 		$redir->{2} = fileno($fh);
 	}
diff --git a/lib/PublicInbox/GitHTTPBackend.pm b/lib/PublicInbox/GitHTTPBackend.pm
index c8878145..a8337035 100644
--- a/lib/PublicInbox/GitHTTPBackend.pm
+++ b/lib/PublicInbox/GitHTTPBackend.pm
@@ -12,6 +12,7 @@ use HTTP::Date qw(time2str);
 use HTTP::Status qw(status_message);
 use Plack::Util;
 use PublicInbox::Qspawn;
+use PublicInbox::Tmpfile;
 
 # 32 is same as the git-daemon connection limit
 my $default_limiter = PublicInbox::Qspawn::Limiter->new(32);
@@ -218,7 +219,8 @@ sub input_prepare {
 	if (defined $fd && $fd >= 0) {
 		return { 0 => $fd };
 	}
-	open(my $in, '+>', undef);
+	my $id = "git-http.input.$env->{REMOTE_HOST}:$env->{REMOTE_PORT}";
+	my $in = tmpfile($id);
 	unless (defined $in) {
 		err($env, "could not open temporary file: $!");
 		return;
diff --git a/lib/PublicInbox/HTTP.pm b/lib/PublicInbox/HTTP.pm
index 19b57d59..b43ef870 100644
--- a/lib/PublicInbox/HTTP.pm
+++ b/lib/PublicInbox/HTTP.pm
@@ -21,6 +21,7 @@ use IO::Handle;
 require PublicInbox::EvCleanup;
 use PublicInbox::DS qw(msg_more);
 use PublicInbox::Syscall qw(EPOLLIN EPOLLONESHOT);
+use PublicInbox::Tmpfile;
 use constant {
 	CHUNK_START => -1,   # [a-f0-9]+\r\n
 	CHUNK_END => -2,     # \r\n
@@ -325,8 +326,9 @@ sub response_write {
 }
 
 sub input_tmpfile ($) {
-	open($_[0], '+>', undef);
-	$_[0]->autoflush(1);
+	my $input = tmpfile('http.input', $_[0]->{sock}) or return;
+	$input->autoflush(1);
+	$input;
 }
 
 sub input_prepare {
@@ -338,10 +340,10 @@ sub input_prepare {
 			quit($self, 413);
 			return;
 		}
-		input_tmpfile($input);
+		$input = input_tmpfile($self);
 	} elsif (env_chunked($env)) {
 		$len = CHUNK_START;
-		input_tmpfile($input);
+		$input = input_tmpfile($self);
 	} else {
 		$input = $null_io;
 	}
diff --git a/lib/PublicInbox/SolverGit.pm b/lib/PublicInbox/SolverGit.pm
index 49f94895..8878961e 100644
--- a/lib/PublicInbox/SolverGit.pm
+++ b/lib/PublicInbox/SolverGit.pm
@@ -15,6 +15,7 @@ use Fcntl qw(SEEK_SET);
 use PublicInbox::Git qw(git_unquote git_quote);
 use PublicInbox::MsgIter qw(msg_iter msg_part_text);
 use PublicInbox::Qspawn;
+use PublicInbox::Tmpfile;
 use URI::Escape qw(uri_escape_utf8);
 
 # POSIX requires _POSIX_ARG_MAX >= 4096, and xargs is required to
@@ -235,7 +236,7 @@ sub prepare_index ($) {
 	my $path_a = $di->{path_a} or die "BUG: path_a missing for $oid_full";
 	my $mode_a = $di->{mode_a} || extract_old_mode($di);
 
-	open my $in, '+>', undef or die "open: $!";
+	my $in = tmpfile("update-index.$oid_full") or die "tmpfile: $!";
 	print $in "$mode_a $oid_full\t$path_a\0" or die "print: $!";
 	$in->flush or die "flush: $!";
 	sysseek($in, 0, 0) or die "seek: $!";
diff --git a/lib/PublicInbox/Tmpfile.pm b/lib/PublicInbox/Tmpfile.pm
new file mode 100644
index 00000000..7fda100e
--- /dev/null
+++ b/lib/PublicInbox/Tmpfile.pm
@@ -0,0 +1,38 @@
+# Copyright (C) 2019 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+package PublicInbox::Tmpfile;
+use strict;
+use warnings;
+use base qw(Exporter);
+our @EXPORT = qw(tmpfile);
+use Fcntl qw(:DEFAULT);
+use Errno qw(EEXIST);
+require File::Spec;
+
+# use tmpfile instead of open(..., '+>', undef) so we can get an
+# unlinked filename which makes sense when viewed with lsof
+# (at least on Linux)
+# TODO: O_APPEND support (this is the reason I'm not using File::Temp)
+# And if we ever stop caring to have debuggable filenames, O_TMPFILE :)
+sub tmpfile ($;$) {
+	my ($id, $sock) = @_;
+	if (defined $sock) {
+		# add the socket inode number so we can figure out which
+		# socket it belongs to
+		my @st = stat($sock);
+		$id .= '-ino:'.$st[1];
+	}
+	$id =~ tr!/!^!;
+
+	my $fl = O_RDWR | O_CREAT | O_EXCL;
+	do {
+		my $fn = File::Spec->tmpdir . "/$id-".time.'-'.rand;
+		if (sysopen(my $fh, $fn, $fl, 0600)) { # likely
+			unlink($fn) or die "unlink($fn): $!"; # FS broken
+			return $fh; # success
+		}
+	} while ($! == EEXIST);
+	undef  # EMFILE/ENFILE/ENOSPC/ENOMEM
+}
+
+1;
diff --git a/lib/PublicInbox/ViewVCS.pm b/lib/PublicInbox/ViewVCS.pm
index 60a62e57..369afe93 100644
--- a/lib/PublicInbox/ViewVCS.pm
+++ b/lib/PublicInbox/ViewVCS.pm
@@ -20,6 +20,7 @@ use bytes (); # only for bytes::length
 use PublicInbox::SolverGit;
 use PublicInbox::WwwStream;
 use PublicInbox::Linkify;
+use PublicInbox::Tmpfile;
 use PublicInbox::Hval qw(ascii_html to_filename);
 my $hl = eval {
 	require PublicInbox::HlMod;
@@ -185,7 +186,7 @@ sub show ($$;$) {
 		$hints->{$to} = $v;
 	}
 
-	open my $log, '+>', undef or die "open: $!";
+	my $log = tmpfile("solve.$oid_b");
 	my $solver = PublicInbox::SolverGit->new($ctx->{-inbox}, sub {
 		solve_result($ctx, $_[0], $log, $hints, $fn);
 	});