On 03/20/2018 11:52 AM, Albrecht Dreß wrote:
Hi all,
I use Postgres 10.3 on a Debian Stretch system with foreign tables, and
noticed strange LOG messages when accessing them.
The data base setup is basically
---8<------------------------------------------------------------------------------------------
CREATE EXTENSION IF NOT EXISTS postgres_fdw WITH SCHEMA public;
CREATE SERVER ext_server FOREIGN DATA WRAPPER postgres_fdw OPTIONS (
dbname 'ext_db', host 'localhost', updatable 'false');
CREATE FOREIGN TABLE public.ext_table (
[…]
) SERVER ext_server OPTIONS (schema_name 'public', table_name
'some_table', updatable 'false');
---8<------------------------------------------------------------------------------------------
Now I use the following trivial Python2 (psycopg2) code to access the
tables:
---8<------------------------------------------------------------------------------------------
import psycopg2
conn = psycopg2.connect(dbname='my_db')
with conn.cursor() as csr:
csr.execute("SELECT * FROM […] LIMIT 1")
csr.fetchone()
conn.close()
---8<------------------------------------------------------------------------------------------
When I access a “local” table of my_db in the SELECT statement, there is
no LOG message. However, reading from ext_table works just fine, but
the conn.close() statement above triggers the log message
---8<------------------------------------------------------------------------------------------
[time stamp/pid] user@my_db LOG: could not receive data from client:
Connection reset by peer
---8<------------------------------------------------------------------------------------------
Did I miss something in the setup here? Or is there any other way to
get rid of the message (which fills ~95% of my logs)?
My suspicion is it has to do with this:
https://www.postgresql.org/docs/10/static/postgres-fdw.html#id-1.11.7.43.10
"
F.34.2. Connection Management
postgres_fdw establishes a connection to a foreign server during the
first query that uses a foreign table associated with the foreign
server. This connection is kept and re-used for subsequent queries in
the same session. However, if multiple user identities (user mappings)
are used to access the foreign server, a connection is established for
each user mapping.
"
Guessing that conn.close() is not closing the internal FDW connection
properly. Not sure how to fix, I will ponder some though.
Thanks in advance,
Albrecht.
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
