watch: support imap.fetchBatchSize parameter

IMAP allows retrieving multiple messages with a single command,
and Mail::IMAPClient supports that.  Unfortunately, it means we
slurp multiple messages into memory at once.  This option allows
users to trade off memory usage to reduce network round-trips.

Ideally, we'd support pipelining; but AFAIK no widely installed
Perl IMAP library supports it.

diff --git a/lib/PublicInbox/WatchMaildir.pm b/lib/PublicInbox/WatchMaildir.pm
index d492e5d65b7c8ffa369b7e402b166cb0ff16deab..05aa6594147dd37df0f16085d49b33da4ad4ddac 100644 (file)
--- a/lib/PublicInbox/WatchMaildir.pm
+++ b/lib/PublicInbox/WatchMaildir.pm
@@ -274,6 +274,15 @@ sub imap_common_init ($) {
                $self->{imap_opt}->{$sec}->{poll_intvl} = $to if $to;
                $to = cfg_intvl($cfg, 'imap', 'IdleInterval', $sec, $url);
                $self->{imap_opt}->{$sec}->{idle_intvl} = $to if $to;
+
+               my $key = lc("imap.$sec.fetchBatchSize");
+               my $bs = $cfg->{lc($key)} //
+                       $cfg->urlmatch('imap.fetchBatchSize', $url) // next;
+               if ($bs =~ /\A([0-9]+)\z/) {
+                       $self->{imap_opt}->{$sec}->{batch_size} = $bs;
+               } else {
+                       warn "W: $key=$bs is not an integer\n";
+               }
        }
        $mic_args;
 }
@@ -389,25 +398,31 @@ sub imap_fetch_all ($$$) {
 
        warn "I: $url fetching UID $l_uid:$r_uid\n";
        $mic->Uid(1); # the default, we hope
-       my $uids;
+       my $bs = $self->{imap_opt}->{$sec}->{batch_size} // 1;
        my $req = $mic->imap4rev1 ? 'BODY.PEEK[]' : 'RFC822.PEEK';
+
+       # TODO: FLAGS may be useful for personal use
        my $key = $req;
        $key =~ s/\.PEEK//;
-       my $uid;
+       my ($uids, $batch);
        my $warn_cb = $SIG{__WARN__} || sub { print STDERR @_ };
        local $SIG{__WARN__} = sub {
-               $uid //= -1;
-               $warn_cb->("$url UID:$uid\n");
+               $batch //= '?';
+               $warn_cb->("$url UID:$batch\n");
                $warn_cb->(@_);
        };
        my $err;
        do {
+               # I wish "UID FETCH $START:*" could work, but:
+               # 1) servers do not need to return results in any order
+               # 2) Mail::IMAPClient doesn't offer a streaming API
                $uids = $mic->search("UID $l_uid:*") or
                        return "E: $url UID SEARCH $l_uid:* error: $!";
                return if scalar(@$uids) == 0;
 
                # RFC 3501 doesn't seem to indicate order of UID SEARCH
-               # responses, so sort it ourselves
+               # responses, so sort it ourselves.  Order matters so
+               # IMAPTracker can store the newest UID.
                @$uids = sort { $a <=> $b } @$uids;
 
                # Did we actually get new messages?
@@ -416,17 +431,23 @@ sub imap_fetch_all ($$$) {
                $l_uid = $uids->[-1] + 1; # for next search
                my $last_uid;
 
-               while (defined(($uid = shift(@$uids)))) {
-                       local $0 = "UID:$uid $mbx $sec";
-                       my $r = $mic->fetch_hash($uid, $req);
+               while (scalar @$uids) {
+                       my @batch = splice(@$uids, 0, $bs);
+                       $batch = join(',', @batch);
+                       local $0 = "UID:$batch $mbx $sec";
+                       my $r = $mic->fetch_hash($batch, $req);
                        unless ($r) { # network error?
-                               $err = "E: $url UID FETCH $uid error: $!";
+                               $err = "E: $url UID FETCH $batch error: $!";
                                last;
                        }
-                       # messages get deleted, so holes appear
-                       defined(my $raw = delete $r->{$uid}->{$key}) or next;
-                       imap_import_msg($self, $url, $uid, \$raw);
-                       $last_uid = $uid;
+                       for my $uid (@batch) {
+                               # messages get deleted, so holes appear
+                               my $per_uid = delete $r->{$uid} // next;
+                               my $raw = delete($per_uid->{$key}) // next;
+                               imap_import_msg($self, $url, $uid, \$raw);
+                               $last_uid = $uid;
+                               last if $self->{quit};
+                       }
                        last if $self->{quit};
                }
                _done_for_now($self);