[pgpool-hackers: 1507] Re: kind does not match error in pgpool

Ahsan Hadi ahsan.hadi at enterprisedb.com
Tue Apr 19 17:50:06 JST 2016

I agree this cause lot of annoyance to pgpool users and something we should
address for 3.6.

Is this added to 3.6 wiki?

On Fri, Apr 15, 2016 at 11:46 AM, Muhammad Usama <m.usama at gmail.com> wrote:

> Hi
> pgpool throws ".. kind does not match.." error message when all the
> attached backend nodes do not return the same response to the query. Although
> this error message can be a symptom of the backend node sync issue in
> most cases, but in case when the message kind of backend nodes differs
> because one of the backend returned the notice response while the other
> returned some other kind then that case should not be considered as an
> error case.
> Consider the scenario where a pgpool is connected to three backend nodes
> and pgpool is expecting to receive "[C] command complete" message from
> all nodes for the last query. But while processing the query one of the
> backend also produced a warning message.
> ... WARNING: database "testdb" must be vacuum within 11000000 transaction
> Please note that the query was successful on all attached backend, but one
> backend also produced an extra warning message along with the command
> complete message.
> Now pgpool will throw an error something like
> ERROR: pid 720: read_kind_from_backend: 1 th kind N does not match
> with master or majority connection kind C
> But since the node would also have sent the expected command complete
> message after that warning notice, So Ideally, pgpool should ignore the
> WARNING message and compare the subsequent message, and only throw an error
> if the message from nodes after ignoring notification messages differs.
> What are your thoughts on this?
> Kind regards
> Muhammad Usama
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Ahsan Hadi
Snr Director Product Development
EnterpriseDB Corporation
The Enterprise Postgres Company

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