Re: [Sqlrelay-discussion] "Too many listeners" error

[David M. <dav...@fi...>]

Hello Andrew,

The maxlisteners parameter can be tuned to manage that error.

SQL Relay opens a set number of connections to the database, then when 
clients connects to the SQL Relay listener, it hands them off to an 
available database connection.  If there are no available connections, 
the listener forks off a child which waits until there is an available 
connection.  The maxlisteners parameter controls how many of these 
forked-off-children can pile up before errors will be thrown.  
Originally, SQL Relay allowed an unlimited number, but some folks 
requested that it be possible to place a limit to prevent the system 
from paging if a lot of clients piled up, so I added that feature.  
Setting maxlisteners="0" should revert to the original behavior and 
allow an unlimited number.

The appropriate value for that number is application-specific, but 10 
would likely be a low number for most applications.

Typical situations that cause clients to pile up would be if the 
database went down for a while or if there are queries that take a long 
time to run that get triggered regularly.

I hope this helps.

David Muse
dav...@fi...

On 07/28/2011 11:41 PM, Andrew L wrote:
> Hi,
>
> I'm using rudiments-0.32 and sqlrelay-0.39.4  .
>
> I have the following Perl code:
>
>     1 ....
>     2 $stmt = 'begin :cursor := my_func; end;';
>     3 $curs->prepareQuery ($stmt);
>     4 $curs->defineOutputBindCursor("cursor");
>     5 $curs->executeQuery() || die "Can't retrieve data from database: 
> " . $curs->errorMessage();
>     7 ....
>
> The script dies at line 5 with "Can't retrieve data from database: Too 
> many listeners" error message.
>
> Here's what I have in my sqlrelay.conf file:
>
> <instance id="my_id"                 port="9000"          dbase="oracle8"
>             connections="5"           maxconnections="30"  
> maxqueuelength="5"
>             growby="1"                ttl="600"            
> endofsession="rollback"    sessiontimeout="600"
>             runasuser="spock"         
> runasgroup="vulcan"               cursors="10"
>             authtier="listener"       
> handoff="pass"                    deniedips=""  allowedips=""
>             debug="listener_and_connection"   
> maxquerysize="65536"      maxstringbindvaluelength="4000"
>             maxlobbindvaluelength="71680"  idleclienttimeout="5"
>             maxlisteners="10"         listenertimeout="0"
>             reloginatstart="false">
>
> What settings do i need to change to fix the error?
>
>
> Thanks
> --Andrew
>
>
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