BDR, near xid wraparound, a lot of files in pg_subtrans directory

HI list,

I have a database with bdr environment which keep alerting these messages
in log file:

HINT: Close open transactions soon to avoid wraparound problems.
WARNING: oldest xmin is far in the past

Querying pg_stat_activity where state='active';

datname | template1
query | autovacuum: VACUUM pg_catalog.pg_depend (to prevent
wraparound)

datname | template1
query | autovacuum: VACUUM pg_toast.pg_toast_1255 (to prevent
wraparound)

datname | template1
query | autovacuum: VACUUM pg_catalog.pg_ts_parser (to prevent
wraparound)

SELECT
pg_namespace.nspname
,c.relname AS relname
,greatest(age(c.relfrozenxid),age(t.relfrozenxid)) as age
,c.relfrozenxid
,t.relfrozenxid
FROM pg_class c
LEFT JOIN pg_class t ON c.reltoastrelid = t.oid
LEFT JOIN
pg_namespace
ON pg_namespace.oid = c.relnamespace
WHERE c.relkind = 'r' and c.relname='pg_depend';

-[ RECORD 1 ]+-----------
nspname | pg_catalog
relname | pg_depend
age | 1165907267
relfrozenxid | 102246720
relfrozenxid |

Trying to vacuum manual, but no luck:

postgres=# vacuum pg_catalog.pg_depend;
WARNING: oldest xmin is far in the past
HINT: Close open transactions soon to avoid wraparound problems.
VACUUM
postgres=# vacuum freeze pg_catalog.pg_depend;
WARNING: oldest xmin is far in the past
HINT: Close open transactions soon to avoid wraparound problems.
VACUUM
postgres=# vacuum full pg_catalog.pg_depend;
WARNING: oldest xmin is far in the past
HINT: Close open transactions soon to avoid wraparound problems.
VACUUM

Check fozenxid again after vacuum, not moving:

SELECT
pg_namespace.nspname
,c.relname AS relname
,greatest(age(c.relfrozenxid),age(t.relfrozenxid)) as age
,c.relfrozenxid
,t.relfrozenxid
FROM pg_class c
LEFT JOIN pg_class t ON c.reltoastrelid = t.oid
LEFT JOIN
pg_namespace
ON pg_namespace.oid = c.relnamespace
WHERE c.relkind = 'r' and c.relname='pg_depend';
-[ RECORD 1 ]+-----------
nspname | pg_catalog
relname | pg_depend
age | 1165908742
relfrozenxid | 102246720
relfrozenxid |

Searching the similar situation, found this url:
https://postgrespro.com/list/thread-id/1556972

but the above url was in streaming replication, not bdr; but symptom is
likely same:
there are a lot of files inside pg_subtrans directory, many files older
than latest cluster restarted.

query pg_prepared_xacts, pg_stat_activity, pg_locks with no indication
about long running queries or even open transactions.

--
regards

ujang jaenudin | DBA Consultant (Freelancer)
http://ora62.wordpress.com
http://id.linkedin.com/pub/ujang-jaenudin/12/64/bab