Re: ODBC cliens is hanging if network connection is broken

Hi,

On 2018/07/07 21:37, [email protected] wrote:
> Hello PostgreSQL Community!
>
> I downloaded and installed the latest version of PostgreSQL from 
> https://www.postgresql.org/ftp/source/v10.4/on my SLES 12 system.
> Here is my configuration of unixODBC:
>
> odbcinst,ini
> [PostgreSQL]
> Description=PostgreSQL ODBC driver
> Driver=/usr/local/lib/psqlodbcw.so
> FileUsage=1
>
> odbc.ini
> [sles12-1]
> Description = PostgreSQL connection to rtpdb
> Driver = PostgreSQL
> Database = rtpdb
> Servername = sles12-1
> Username =
> Password =
> Port = 5432
> Protocol = 7.4+
> ReadOnly = No
> RowVersioning = No
> ShowSystemTables = No
> ConnSettings =
>
> As a Driver in odbcinst.ini I specified the path to *psqlodbcw.so 
> *which was downloaded from 
> https://git.postgresql.org/gitweb/?p=psqlodbc.gitand built as follows:
> ./configure
> make
> make install
>
> Could you please provide a comment concerning the following situation?
>
> I  created a simple ODBC program which calls "*SELECT 
> pg_is_in_recovery()*" on the remote PostgreSQL server using ODBC API. 
> It works good with this ODBC configuration. But as soon as I turn off 
> network interface after *SQLConnect *call and before *SQLExecDirect*, 
> it leads to *SQLExecDirect *hanging.
>
> I tried to use *statement_timeout* and 
> *idle_in_transaction_session_timeout* postgresql configuration 
> parameters but they were not suitable for network issue case. These 
> parameters define server-side behaviour but a client considers that 
> the connection is ok and it is hanging.

>
>
> As far as I know *SQL_ATTR_CONNECTION_TIMEOUT *ODBC attribute could 
> handle this situation. Another ODBC driver for another database in 
> case of similar situation returns *HYT01 *ODBC error (Connection 
> timeout expired) . But I guess *SQL_ATTR_CONNECTION_TIMEOUT * is not 
> supported by psqlodbc.  Am I right?

How about calling SQLSetStmtAttr() with the attribute parameter 
SQL_ATTR_QUERY_TIMEOUT?

>
>
> PostgreSQL JDBC driver provides *socketTimeout*property which helps a 
> client to be informed about network problems and to avoid an infinite 
> hanging.
> In my tests it returned *08006 *sqlstate (*connection_failure*).
>
> So I have a question. Is there any psqlodbc or native PostgreSQL 
> mechanism or configuration parameter which helps a client to be 
> informed about network problem?
> Is there any mechanism which helps to avoid this infinite hanging for 
> SQL query in this case?
>
> Thank You in advance,
> Andrei Yahorau