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Port Bug Report: Backend processeses hang when remote connections break.

From: Unprivileged user <nobody>
To: pgsql-ports(at)postgresql(dot)org
Subject: Port Bug Report: Backend processeses hang when remote connections break.
Date: 1999-01-02 10:41:09
Message-ID: 199901021041.FAA05109@hub.org (view raw or flat)
Thread:
Lists: pgsql-ports
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                        POSTGRESQL BUG REPORT TEMPLATE
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Your name		: Juan Alvarez Ferrando
Your email address	: jferrando(at)acm(dot)org

Category		: runtime: back-end
Severity		: serious

Summary: Backend processeses hang when remote connections break.

System Configuration
--------------------
  Operating System   : Linux 2.0.36 ELF (Suse 5.3)

  PostgreSQL version : 6.0

  Compiler used      : Precompiled

Hardware:
---------
Pentium II 333MHZ, 128MB RAM, 4GB SCSI HDD

Versions of other tools:
------------------------


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Problem Description:
--------------------
When the network connection to the backend breaks (for 
example if you pull out the cable from the NIC, or switch
off the modem), the backend process that attended the 
connection hangs and never dies. This fills the backend 
limit of 64 and the database blocks.

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Test Case:
----------
Have postgersql configured for TCP/IP connections and
password user identification.
Make a ps in the server to see what backends are opened
(the postgres processes).
Open a frontend or client program that connects to de 
database.
Make a query to check that the connection works fine.
Make a ps to get the process that corresponds to your 
connection.
Unplug the network cable from the NIC, or switch off the
modem.
Make another query to see how it fails (exception 'Connection reset by  peer' when using JDBC).
Make a ps in the server machine and see how the process is
still there.
Plug in the cable again or reconnect to your ISP, and see 
how the connection is not restored, so you have to open
a new frontend to get a new database connection (new
process in the server).
As it seems, the TCP/IP connection is broken but the backend
is not informed of this. When a software crash occurs the
backend does dissapear, so it seems a bit strange.

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Solution:
---------


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