I had the same issue... A slave server had missing wal_files... and it wasn't synced.
I had to re-sync all the DB, by running the pg_basebackup command.... So.. basically, what I did is: 1 - Ensure that the wal_files are being inserted into the slave 2 - Backup the recovery.conf, postgresql.conf and pg_hba.conf 3 - Delete all the current data folder, by doing: rm -rf /var/lib/pgsql/9.2/data/* 4 - Running the pg_basebackup command to re-sync the DB from another slave to the slave that I wanna fix 5 - Replace the .conf backup files into the new data folder 6 - Start postgres And it worked nice.... Patrick