We were using chainsaw to monitor WL 8.1 too, using a SocketHubAppender (so that
multiple chainsaw clients could easily connect to receive the logs) - it's especially
useful for us because we don't have direct access to the drive that hosts the log
files (we have to access them via a web portal). We found that if chainsaw was left
connected to the server, collecting log events over a long period of time but not
being looked at (eg over a lunch break) we could hang all the EJBs that used log4j.
We've now switched to a JMSAppender, writing to a non-persistent topic with a short
TTL (a few seconds, I think). It's more complicated than a SocketHubAppender and has
its own problems (including that you can no longer run chainsaw using webstart, due to
a bug in weblogic preventing it being used with webstart), but it should be completely
safe in a production environment.
As I understand it, an AsyncAppender wouldn't actually prevent this kind of issue -
just delay it... when the AsyncAppender's buffer also fills up, it'll hang in the same
way (correct me if I'm wrong?)
Cheers,
Stephen
Jeff Longland
<[EMAIL PROTECTED]> To: Log4J Users List <[EMAIL
PROTECTED]>
cc:
17/09/2004 01:11 Subject: Re: WebLogic 8.1 and Chainsaw
Please respond to
"Log4J Users
List"
Just took a look at the docs for AsyncAppender - because it runs on its
own thread, should Chainsaw ever hang - the only thing affected is
logging, correct?
I'm in complete agreement Paul - "The penalty, like the normal cost of
any logging, is often worth the price". It was suggested to me that if
I wanted to monitor a production system with Chainsaw that I should
consider binding traffic to a different network interface. This would
alleviate some network traffic, but not the overhead of serializing.
Generally speaking, what sort of resources does a socket(hub)appender
consume?
Jeff
Paul Smith wrote:
>>I'm currently administering a Java app running on WebLogic 8.1. The app
>>uses log4j to handle logging events and I have setup a few socket
>>appenders to monitor classes important in our day-to-day operations.
>>Chainsaw has been great for staying on top of critical errors real-time
>>instead of the traditional tail/grep/less method. While speaking with a
>>vendor rep, I was informed that running Chainsaw could be detrimental to
>>a production system. The vendor's belief is that a hang in the Chainsaw
>>client could cause WebLogic to hang. I was just curious if there's any
>>validity to such a claim?
>
>
> It is potentially possible that a hang in a Chainsaw client could prevent
> the server thread that is doing the appending from continuing, which is why
> you could consider wrapping the SocketAppender or SocketHubAppender in a
> AsyncAppender. Shutting down Chainsaw or killing it would free that thread
> immediately though.
>
> I've never had any problems monitoring a production box with Chainsaw.
> Under seriously loaded systems the cost of sending the data over the socket
> could add some delays, but then when it's under load, you're probably
> interested in what's going on anyway.... The penalty, like the normal cost
> of any logging, is often worth the price.
>
> This is all IMHO of course. YMMV.
>
> Paul Smith
>
>
>
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