Re: Memory Leaks when web server hangs

[Eric Bloch]

Hey there,

I create/destroy http clients but always have them use the same 
connection manager.

Will that cause thread thrashing?

Thanks,

-Eric

Roland Weber wrote:

Hello Srini,

you should *not* create a new HTTP Client for each request!
This will also create a new connection manager, and a new
cleanup thread. It beats the whole purpose of connection
management.
You should create *one* HTTP Client object for the lifetime
of your application. Then, the connection manager of that
client will reuse and free connections as appropriate.
best regards,
 Roland




Srinivas Vemula <[EMAIL PROTECTED]>
02.02.2004 11:56
Please respond to "Commons HttpClient Project"
       To:     Commons HttpClient Project 
<[EMAIL PROTECTED]>
       cc: 
       Subject:        Re: Memory Leaks when web server hangs

Oleg,

   We are using JDK1.4.1 and connection time out is set to 30Ms and 
read time out to 60Ms. We are trying to connect to a IP Camera, and send 
a heart beat command to the camera to check for its availability every 
30 Secs from the time we find it is un available. If the web server is 
down, we feel that HttpClient is not cleaning up failed connections 
properly and thats resulting in Memory Leaks at the server side.

   The code we use is the standard way of using HttpClient and all the 
code is in a method and new HttpClient object is created for every 
request. Are there any ways to make sure the connections are all being 
purged properly? Are there any precautionary measures or flags we can 
set on HttpClient API when communicating with a web server (running on 
firm ware) with relatively less RAM and processing power (IpCamera with 
built in web server)?

Thanks for your time and help.
Srini
Kalnichevski, Oleg wrote:

 

Mike and Oleg, the stack trace Srini included indicates that HttpClient 
     

is
 

attempting to create a new timeout thread on every connection - does 
     

this
 

always occur or is it just one timeout thread per httpclient instance? 
     

It
 

would be ideal if we could reduce this to one static thread as starting
threads is never nice for server side apps.  Not sure how feasible that 
     

is
 

though.

     

Hi Srini,
HttpClient uses an additional controller thread to work around the 
   

limitation of older (< 1.4) JDKs which do not provide a possibility to set 
connect timeout. If you do not really need to control connect timeout (for 
instance, when communicating with an intranet site with good availability) 
simply set connect timeout to. That will prevent HttpClient from spawning 
an additional thread per request.
 

Adrian, et al
Another possibility to use reflection to set connect timeout using the 
   

Socket methods when running in JVM 1.4 or above
 

Oleg



-----Original Message-----
From: Adrian Sutton [mailto:[EMAIL PROTECTED]
Sent: Monday, February 02, 2004 09:03
To: Commons HttpClient Project
Subject: Re: Memory Leaks when web server hangs
On 2/2/04 2:00 PM, "Srinivas Vemula" <[EMAIL PROTECTED]> 
   

wrote:
 

   

Hi All,
    We are seeing thread leaks when having client open connections to 
     

a web
 

server that hangs. Has any one seen this happening?? How do we ensure 
     

that the
 

library correctly closes  socket connections on failures, cleaning up 
     

system
 

resources, and  threads actually finish in  the timeout period and get 
     

freed
 

up. Would using MultiThreadedHttpConnectionManager
<
     

file:///D:/silkroad/http-commons/commons-httpclient-2.0-rc3/docs/threading.ht

 

ml#MultiThreadedHttpConnectionManager>   be of any help??

     

Hi Srini,
If you're using the same HttpClient instance across multiple threads, you
must use the MultiThreadedHttpConnectionManager or you'll run into 
   

strange
 

problems.  If you're using separate HttpClient instances, you may as well
stick with the single threaded (default) connection manager.
In terms of connections hanging - you probably want to look into the
setConnectionTimeout and setTimeout methods of the HttpClient class. 
   

These
 

allow you to control how long HttpClient waits when making a connection 
   

and
 

how long it waits for data once the connection is established.  If you 
   

have
 

set either of these to 0 (not sure what the default is, it may be 
   

platform
 

specific) the connection will never timeout which sounds a lot like what
you're seeing.
Mike and Oleg, the stack trace Srini included indicates that HttpClient 
   

is
 

attempting to create a new timeout thread on every connection - does this
always occur or is it just one timeout thread per httpclient instance? It
would be ideal if we could reduce this to one static thread as starting
threads is never nice for server side apps.  Not sure how feasible that 
   

is
 

though.



   

Srini

     

Regards,

Adrian Sutton.

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