remote_apply for logical replication?

Hi,

In src/backend/replication/logical/worker.c:

pq_sendbyte(reply_message, 'r');
pq_sendint64(reply_message, recvpos); /* write */
pq_sendint64(reply_message, flushpos); /* flush */
pq_sendint64(reply_message, writepos); /* apply */

Is 'writepos' really applied? Why do we report the merely received
position as written?

I haven't tried any of this stuff out yet so this may be a stupid
question, but I'm wondering: should xinfo &
XACT_COMPLETION_APPLY_FEEDBACK trigger logical replication to send a
reply, so that synchronous_commit = remote_apply would work?

--
Thomas Munro
http://www.enterprisedb.com