xcpdb: implement progress reporting

Copying an entire Xapian DB is horribly slow whether it's done
via Perl or copydatabase(1).  So displaying some progress
indication is good for user experience.

While we're at it, prefix xapian-compact output, too; since
parallel processes end up clobbering each other.

1 files changed, 43 insertions, 4 deletions

diff --git a/lib/PublicInbox/Xapcmd.pm b/lib/PublicInbox/Xapcmd.pm
index 4555340a..99f0e7c1 100644
--- a/lib/PublicInbox/Xapcmd.pm
+++ b/lib/PublicInbox/Xapcmd.pm
@@ -82,9 +82,21 @@ sub prepare_reindex ($$) {
         }
 }
 
+sub progress_prepare ($) {
+        my ($opt) = @_;
+        if ($opt->{quiet}) {
+                open my $null, '>', '/dev/null' or
+                        die "failed to open /dev/null: $!\n";
+                $opt->{1} = fileno($null);
+                $opt->{-dev_null} = $null;
+        } else {
+                $opt->{-progress} = 1;
+        }
+}
+
 sub run {
         my ($ibx, $cmd, $env, $opt) = @_;
-        $opt ||= {};
+        progress_prepare($opt ||= {});
         my $dir = $ibx->{mainrepo} or die "no mainrepo in inbox\n";
         my $exe = $cmd->[0];
         my $pfx = $exe;
@@ -161,6 +173,8 @@ sub cpdb_retryable ($$) {
         0;
 }
 
+# Like copydatabase(1), this is horribly slow; and it doesn't seem due
+# to the overhead of Perl.
 sub cpdb {
         my ($args, $env, $opt) = @_;
         my ($old, $new) = @$args;
@@ -172,6 +186,7 @@ sub cpdb {
         my $creat = Search::Xapian::DB_CREATE();
         my $dst = Search::Xapian::WritableDatabase->new($tmp, $creat);
         my ($it, $end);
+        my ($pfx, $nr, $tot, $fmt); # progress output
 
         do {
                 eval {
@@ -181,6 +196,13 @@ sub cpdb {
 
                         $it = $src->postlist_begin('');
                         $end = $src->postlist_end('');
+                        if ($opt->{-progress}) {
+                                $nr = 0;
+                                $pfx = (split('/', $old))[-1].':';
+                                $tot = $src->get_doccount;
+                                $fmt = "$pfx % ".length($tot)."u/$tot\n";
+                                warn "$pfx copying $tot documents\n";
+                        }
                 };
         } while (cpdb_retryable($src, $@));
 
@@ -191,6 +213,9 @@ sub cpdb {
                                 my $doc = $src->get_document($docid);
                                 $dst->replace_document($docid, $doc);
                                 $it->inc;
+                                if ($fmt && !(++$nr & 1023)) {
+                                        warn(sprintf($fmt, $nr));
+                                }
                         }
 
                         # unlike copydatabase(1), we don't copy spelling
@@ -200,10 +225,12 @@ sub cpdb {
                 };
         } while (cpdb_retryable($src, $@));
 
+        warn(sprintf($fmt, $nr)) if $fmt;
         return unless $opt->{compact};
 
         $src = $dst = undef; # flushes and closes
 
+        warn "$pfx compacting...\n" if $pfx;
         # this is probably the best place to do xapian-compact
         # since $dst isn't readable by HTTP or NNTP clients, yet:
         my $cmd = [ $XAPIAN_COMPACT, '--no-renumber', $tmp, $new ];
@@ -212,10 +239,22 @@ sub cpdb {
                 defined(my $dst = $opt->{$fd}) or next;
                 $rdr->{$fd} = $dst;
         }
+
+        my ($r, $w);
+        if ($pfx && pipe($r, $w)) {
+                $rdr->{1} = fileno($w);
+        }
         my $pid = spawn($cmd, $env, $rdr);
-        my $r = waitpid($pid, 0);
-        if ($? || $r != $pid) {
-                die join(' ', @$cmd)." failed: $? (pid=$pid, reaped=$r)\n";
+        if ($pfx) {
+                close $w or die "close: \$w: $!";
+                foreach (<$r>) {
+                        s/\r/\r$pfx /g;
+                        warn "$pfx $_";
+                }
+        }
+        my $rp = waitpid($pid, 0);
+        if ($? || $rp != $pid) {
+                die join(' ', @$cmd)." failed: $? (pid=$pid, reaped=$rp)\n";
         }
         remove_tree($tmp) or die "failed to remove $tmp: $!\n";
 }