Re: Extremely slow to establish connection when user has a high number of roles

Michal Charemza <michal(at)charemza(dot)name> writes:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>> I'm fairly sure that if that exists it's always noticed first,
>> bypassing the need for any role membership tests. So please
>> confirm whether your production database has revoked PUBLIC
>> connect privilege.

> I realised that in fact we hadn't revoked this. So it sounds like whatever
> the issue, it's not about checking if the user has the CONNECT privilege?

Yeah. I double-checked the code (see aclmask()), and it will detect
holding a privilege via PUBLIC before it performs any role membership
searches. So whatever is happening, it's not that lookup.

>> It could be that the problem is not associated with the
>> database's connect privilege, but with role membership lookups
>> triggered by pg_hba.conf entries. Do you have any entries there
>> that require testing membership (i.e. the role column is not
>> "all")?

> Running `select * from pg_hba_file_rules` it looks like the user column is
> always {all} or {rdsadmin}

You'll need to look closer and figure out which of the HBA rules is
being used for the slow connection attempts. If it's {rdsadmin}
then that would definitely involve a role membership search.
If it's {all} then we're back to square one.

A different line of thought could be that the slow connections
are slow because they are waiting on a lock that some other
process has got and is in no hurry to release. It would be
worth trying to capture the contents of the pg_locks view
(and I guess also pg_stat_activity) while one of these sessions
is stuck, if you can reproduce it often enough to make that
feasible.

regards, tom lane