Обсуждение: [HACKERS] No parameter values checking while creating Altersubscription...Connection

Hi,

We usually check connection  parameter values while creating create 
subscription

\\port is WRONG

postgres=# create subscription c1 connection 'port=4000 ' publication pub;
ERROR:  could not connect to the publisher: could not connect to server: 
No such file or directory    Is the server running locally and accepting    connections on Unix domain socket
"/tmp/.s.PGSQL.4000"?
postgres=#

\\when database doesn't exist

postgres=# create subscription c1 connection 'dbname=postgre ' 
publication pub;
ERROR:  could not connect to the publisher: FATAL:  database "postgre" 
does not exist
postgres=#

but such checking is not done at the time of alter subscription .. 
connection

postgres=# alter subscription c1 connection 'port=4000';
ALTER SUBSCRIPTION
postgres=# alter subscription c1 connection 'dbname=cc';
ALTER SUBSCRIPTION

-- 
regards,tushar
EnterpriseDB  https://www.enterprisedb.com/
The Enterprise PostgreSQL Company

On Thu, May 25, 2017 at 9:43 AM, tushar <tushar.ahuja@enterprisedb.com> wrote:
> Hi,
>
> We usually check connection  parameter values while creating create
> subscription
>
> \\port is WRONG
>
> postgres=# create subscription c1 connection 'port=4000 ' publication pub;
> ERROR:  could not connect to the publisher: could not connect to server: No
> such file or directory
>     Is the server running locally and accepting
>     connections on Unix domain socket "/tmp/.s.PGSQL.4000"?
> postgres=#
>
> \\when database doesn't exist
>
> postgres=# create subscription c1 connection 'dbname=postgre ' publication
> pub;
> ERROR:  could not connect to the publisher: FATAL:  database "postgre" does
> not exist
> postgres=#
>
> but such checking is not done at the time of alter subscription ..
> connection
>
> postgres=# alter subscription c1 connection 'port=4000';
> ALTER SUBSCRIPTION
> postgres=# alter subscription c1 connection 'dbname=cc';
> ALTER SUBSCRIPTION
>

CREATE SUBSCRIPTION tries to connect to publisher to create
replication slot or to get table list for table synchronization, not
to check the connection parameter value. So if you specify connect =
false then CREATE SUBSCRIPTION doesn't try to connect.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center

On 5/25/17 10:18, Masahiko Sawada wrote:
>> postgres=# alter subscription c1 connection 'port=4000';
>> ALTER SUBSCRIPTION
>> postgres=# alter subscription c1 connection 'dbname=cc';
>> ALTER SUBSCRIPTION
>>
> CREATE SUBSCRIPTION tries to connect to publisher to create
> replication slot or to get table list for table synchronization, not
> to check the connection parameter value. So if you specify connect =
> false then CREATE SUBSCRIPTION doesn't try to connect.

We don't make a connection attempt as part of ALTER SUBSCRIPTION.  I
guess we could just connect and disconnect to check that it works.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

On 2017-05-25 17:08:57 -0400, Peter Eisentraut wrote:
> On 5/25/17 10:18, Masahiko Sawada wrote:
> >> postgres=# alter subscription c1 connection 'port=4000';
> >> ALTER SUBSCRIPTION
> >> postgres=# alter subscription c1 connection 'dbname=cc';
> >> ALTER SUBSCRIPTION
> >>
> > CREATE SUBSCRIPTION tries to connect to publisher to create
> > replication slot or to get table list for table synchronization, not
> > to check the connection parameter value. So if you specify connect =
> > false then CREATE SUBSCRIPTION doesn't try to connect.
> 
> We don't make a connection attempt as part of ALTER SUBSCRIPTION.  I
> guess we could just connect and disconnect to check that it works.

I think during reconfigurations it's quite useful to be able to do so
even if the other hosts aren't reachable that second.

- Andres

On 25/05/17 23:18, Andres Freund wrote:
> On 2017-05-25 17:08:57 -0400, Peter Eisentraut wrote:
>> On 5/25/17 10:18, Masahiko Sawada wrote:
>>>> postgres=# alter subscription c1 connection 'port=4000';
>>>> ALTER SUBSCRIPTION
>>>> postgres=# alter subscription c1 connection 'dbname=cc';
>>>> ALTER SUBSCRIPTION
>>>>
>>> CREATE SUBSCRIPTION tries to connect to publisher to create
>>> replication slot or to get table list for table synchronization, not
>>> to check the connection parameter value. So if you specify connect =
>>> false then CREATE SUBSCRIPTION doesn't try to connect.
>>
>> We don't make a connection attempt as part of ALTER SUBSCRIPTION.  I
>> guess we could just connect and disconnect to check that it works.
> 
> I think during reconfigurations it's quite useful to be able to do so
> even if the other hosts aren't reachable that second.
> 

Yes, it's intended behavior for this very reason, we want ability to
(re)configure downstream without any existing upstream. It's also reason
why we have the WITH (connect = false) in CREATE SUBSCRIPTION. I don't
see a nice way how to do something similar (ie make it optional) for
ALTER though.

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