BUG #15401: pg_dump error

The following bug has been logged on the website:

Bug reference: 15401
Logged by: prakash
Email address: prakash(dot)ramakrishnan(dot)ap(at)nielsen(dot)com
PostgreSQL version: 9.6.6
Operating system: Red Hat Enterprise Linux Server release 7.4 (Maipo
Description:

Hi Team ,

While am connecting the standby server to taking the backup getting below
error.

==> pg_dump -h LHRRHENPPP002.enterprisenet.org -p 5432 -d AIUK01PR -U
postgres -Fd -f /PGDATA/prakash_backup/AIUK01PR.sql
Password:
pg_dump: Dumping the contents of table "cmt_attributes" failed:
PQgetResult() failed.
pg_dump: Error message from server: ERROR: canceling statement due to
conflict with recovery
DETAIL: User was holding a relation lock for too long.
pg_dump: The command was: COPY cmtroi_owner.cmt_attributes (id, cmt_id,
user_id, insert_date, last_change_date, height, width, duration, dpi,
filesize, codec) TO stdout;

Regards,
Prakash.R