lei: bail out earlier on IMAP writer failures

Excessive IMAP connections can overload IMAP servers and cause
clients to be disconnected without diagnostic messages.
Use $lei->fail on these exceptions to propagate errors to the
CLI ASAP to avoid further errors down the line.

This ought to make problems more apparent for users using IMAP
destinations.

Reported-by: Ricardo Ribalda <ribalda@chromium.org>
Link: https://public-inbox.org/meta/CANiDSCsDfutAUMBLPZbxdyka+_jnhv+4YNYdL9QPRoC=wNUGCQ@mail.gmail.com/

1 files changed, 7 insertions, 3 deletions

diff --git a/lib/PublicInbox/LeiToMail.pm b/lib/PublicInbox/LeiToMail.pm
index 2aa3977e..03cbde3b 100644
--- a/lib/PublicInbox/LeiToMail.pm
+++ b/lib/PublicInbox/LeiToMail.pm
@@ -310,8 +310,11 @@ sub _imap_write_cb ($$) {
         my $dedupe = $lei->{dedupe};
         $dedupe->prepare_dedupe if $dedupe;
         my $append = $lei->{net}->can('imap_append');
-        my $uri = $self->{uri};
-        my $mic = $lei->{net}->mic_get($uri);
+        my $uri = $self->{uri} // die 'BUG: no {uri}';
+        my $mic = $lei->{net}->mic_get($uri) // die <<EOM;
+E: $uri connection failed.
+E: Consider using `--jobs ,1' to limit IMAP connections
+EOM
         my $folder = $uri->mailbox;
         $uri->uidvalidity($mic->uidvalidity($folder));
         my $lse = $lei->{lse}; # may be undef
@@ -749,7 +752,8 @@ sub do_post_auth {
                 $au_peers->[1] = undef;
                 sysread($au_peers->[0], my $barrier1, 1);
         }
-        $self->{wcb} = $self->write_cb($lei);
+        eval { $self->{wcb} = $self->write_cb($lei) };
+        $lei->fail($@) if $@;
         if ($au_peers) { # wait for peer l2m to set write_cb
                 $au_peers->[3] = undef;
                 sysread($au_peers->[2], my $barrier2, 1);