Horton

Re: Patch: Implement failover on libpq connect level.

Robert Haas <robertmhaas@gmail.com>

View thread View on postgr.es
From: Robert Haas <robertmhaas@gmail.com>
To: Kuntal Ghosh <kuntalghosh.2007@gmail.com>
Cc: Mithun Cy <mithun.cy@enterprisedb.com>, Catalin Iacob <iacobcatalin@gmail.com>, "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>, Craig Ringer <craig@2ndquadrant.com>, Peter van Hardenberg <pvh@pvh.ca>, Peter Eisentraut <peter_e@gmx.net>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2016-11-29T20:14:48Z
Lists: pgsql-hackers 
On Tue, Nov 29, 2016 at 3:14 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> On Tue, Nov 29, 2016 at 2:19 PM, Kuntal Ghosh
> <kuntalghosh.2007@gmail.com> wrote:
>> On Thu, Nov 24, 2016 at 5:46 PM, Mithun Cy <mithun.cy@enterprisedb.com> wrote:
>>> I have taken this suggestion now renamed target_server_type to
>>> target_session_attrs with possible 2 values "read-write", "any".
>>> May be we could expand to "readonly" and "prefer-readonly" in next patch
>>> proposal. Attaching the patch for same.
>> I was doing some testing with the patch and I found some inconsistency
>> in the error message.
>> I've a read-only server running on port 5433 and no server on 5436 and 5438.
>>
>> command: bin/psql
>> 'postgresql://localhost:5436,localhost:5433,localhost:5438/postgres?target_session_attrs=read-write'
>>
>> I get the following error message.
>>
>> psql: could not make a writable connection to server "localhost:5433"
>> could not connect to server: Connection refused
>>     Is the server running on host "localhost" (::1) and accepting
>>     TCP/IP connections on port 5438?
>> could not connect to server: Connection refused
>>     Is the server running on host "localhost" (127.0.0.1) and accepting
>>     TCP/IP connections on port 5438?
>>
>> It didn't show any error message for port 5436. But, if I modify the
>> connection string as following:
>>
>> command: bin/psql
>> 'postgresql://localhost:5433,localhost:5436,localhost:5438/postgres?target_session_attrs=read-write'
>>
>> I get the following error message:
>>
>> psql: could not make a writable connection to server "localhost:5433"
>> could not connect to server: Connection refused
>>     Is the server running on host "localhost" (::1) and accepting
>>     TCP/IP connections on port 5436?
>> could not connect to server: Connection refused
>>     Is the server running on host "localhost" (127.0.0.1) and accepting
>>     TCP/IP connections on port 5436?
>> could not connect to server: Connection refused
>>     Is the server running on host "localhost" (::1) and accepting
>>     TCP/IP connections on port 5438?
>> could not connect to server: Connection refused
>>     Is the server running on host "localhost" (127.0.0.1) and accepting
>>     TCP/IP connections on port 5438?
>
> Hmm, maybe the query buffer is getting cleared someplace in there.  We
> might need to save/restore it.

Not the query buffer.  conn->errorMessage.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. libpq: Add target_session_attrs parameter.

  2. Remove superuser checks in pgstattuple

  3. Fix unwanted flushing of libpq's input buffer when socket EOF is seen.