Re: BDR, wal segment has been removed, is it possible move forward?

On 6 September 2017 at 08:47, milist ujang <ujang(dot)milist(at)gmail(dot)com> wrote:

> Hi Craig
>
> On Wed, Sep 6, 2017 at 7:21 AM, Craig Ringer <craig(at)2ndquadrant(dot)com>
> wrote:
>>
>>
>> BDR can, see bdr.skip_changes_upto .
>>
>> Unluckily my bdr is 0.9.3
>
>
>> But PostgreSQL's logical decoding requires a contiguous WAL stream to
>> maintain a valid catalog_xmin and restart_lsn, so it'll still fail to
>> advance. So your replication from that node is broken, and you have to part
>> the node then rejoin. You'll need to manually recover any diverged data.
>>
>> Yup, I willing to reconcile data manualy via dblink or else,
> is it still possible to move wal segment in 0.9.3?
>

Well, you can skip changes on the logical decoding stream manually in 0.9.3
using the underlying postgres functions. But it won't help you because what
you broke when you deleted the WAL segments wasn't BDR, it was postgres
logical decoding.

It *requires* a contiguous stream of WAL. It cannot recover if you do not
have that. And you cannot really reset it.

You could drop and re-create the replication slot, I guess. But your nodes
would be hopelessly out of sync and need manual resync (with data
replication disabled) of one node vs another.

--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services