[Firebird-devel] [ firebird-Bugs-943087 ] Events producing high CPU load under certain conditions

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Bugs item #943087, was opened at 2004-04-27 17:14
Message generated for change (Comment added) made by bullestock
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=109028&aid=943087&group_id=9028

Category: Core Engine
Group: Confirmed Bug
Status: Open
Resolution: None
Priority: 7
Submitted By: Bjoern Latte (latte)
Assigned to: Nobody/Anonymous (nobody)
Summary: Events producing high CPU load under certain conditions

Initial Comment:
Clients using events may get a FB1.5 server to hogging
the CPU if connection to clients get lost or are
unstable. All further connections to DBserver will
perform very poor. High load condition can only be
ended by restarting server.

Environs:
Client PC: Windows XP Pro
Server PC: Windows 2000 SP3 and Windows XP Pro SP1
Firebird-1.5.0.4306-Win32


Following procedure will lead to high (99 - 100%) CPU
load on FB 1.5 servers:

- connect a client to a db and register an event
- simulate a bad network connection by disabling NIC on
client PC
- renanable NIC on client PC, connect to db again and
fire the event registered in the first step
-> fbserver will go out and grab the CPU, restart of
server needed to end condition

Source for testapp writen with IBO 4.3.Aa and Delphi 7E
and usage description can be found in the attached file. 
DDL for testapp DB holds only single stored proc as folows:

CREATE PROCEDURE EVENT_POSTING (
EVNAME VARCHAR (50))
AS
BEGIN
POST_EVENT :EVNAME;
exit;
END



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Comment By: Torsten Martinsen (bullestock)
Date: 2004-06-14 11:22

Message:
Logged In: YES 
user_id=382855

I have done some debugging: The high CPU usage is caused by 
the server going into a loop calling packet_receive() in inet.
cpp - the recv() call always returns -1 immmediately when the 
connection has been lost.

Workarounds:

1) Set DummyPacketInterval to a nonzero value in the config 
file

This is probably a bad idea, as the config file explicitly 
discourages this (NOTE: The article referred to (http:
//support.microsoft.com/default.aspx?kbid=296265) concerns 
an issue which was fixed in Win2000 SP3, and it is unclear how 
this is related to Firebird).

2) Change the KeepAliveTime registry setting (as described in 
http://support.microsoft.com/default.aspx?kbid=140325). I 
used 30000, which seems to work.

Both workarounds function by enabling Firebird to detect that 
the connection has been closed.

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Comment By: Torsten Martinsen (bullestock)
Date: 2004-06-12 22:18

Message:
Logged In: YES 
user_id=382855

I have confirmed this bug using a simple C++ test program 
(using the IBPP library) with the FB server running on

- Windows 2000 Server, dual Athlon 1 GHz (only the first CPU 
goes to 100 %)
- Windows XP Professional, Pentium IV 2.5 GHz

----------------------------------------------------------------------

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