让 PostgreSQL BDR 在没有超级用户（postgres 用户）权限的情况下工作？

Question

We're switching from MongoDB to Postgres at work, and I'm setting up a BDR group.

At this step I'm looking at security and locking down where possible. Hence, I was hoping to set up a replication user (role) and let BDR use that for its replication stuff. I already had the group happily running when using either trusted connections or the postgres user for authentication. Neither seems 100% secure to me, and I particularly don't like how the postgres user's password would appear in clear text in the DSN connections strings in bdr.bdr_nodes . So I tried using this replication user instead.

That is, eg in pg_hba.conf :

hostssl appdb,replication replication 172.17.1.2 md5

And the matching DSN connection string,

host=172.17.1.1 dbname=appdb user=replication password=secret

Problem with this approach is illustrated by the following error when issuing bdr.bdr_group_create :

ERROR:  local dsn does not have superuser rights
DETAIL:  The dsn 'host=172.17.1.1 dbname=appdb user=replication password=secret' connects successfully but does not grant superuser rights

And this is where I'm a bit puzzled. Does BDR really need superuser rights for replication? Or can I grant specific privileges to my replication role that'll allow it to do its business without being all-powerful?

Maybe it's just me being paranoid, but I feel that the postgres user should only be used for sysadmin stuff, and that the password to it most definitely shouldn't appear in a table in a cleartext DSN connection string, even if you require special privileges to read from said table.

Answer 1

At this time you can't use BDR without a superuser connection for replication. It's required by logical decoding. We're hoping to address that in the 9.6 edition of BDR.

Please think very carefully about whether you truly need multi-master before going down this path. Are you sure an active/standby setup, with read replicas, isn't sufficient for your needs? Please read the manual section on BDR's limitations and the additional application development considerations carefully.