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Date: Tue, 12 Feb 2013 10:11:07 -0500
From: Phillip Odam <phillip.odam@nitorgroup.com>
Reply-To: phillip.odam@nitorgroup.com
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To: James Users List <server-user@james.apache.org>
Subject: Re: Using connectionBacklog
References: <511920A9.5000004@nitorgroup.com> <5119E542.40708@apache.org>
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Thanks for the response Eric.

I must admit I had thought the backlog count would not include the 
current connections. However when testing I also tried a greater number 
for backlog e.g.

connectionBacklog = 200
connectionLimit = 1

And I'm still only able to make one connection and all subsequent 
connections are immediately rejected. Has anyone seen backlog working in 
james?

Phillip

On 2/12/13 1:46 AM, Eric Charles wrote:
> Hi,
>
> If you set backlog=1, the socket can not queue more than one request at
> a time. So if the socket is already busy with one connection, a second
> connection request will be simply rejected. The backlog property is
> given to netty for its bootstrap.
>
> The connectionLimit is implemented with Netty handlers which rejects
> connection if you have already more open connection than the given number.
>
> Thx, Eric
>
>
> On 11/02/2013 16:47, Phillip Odam wrote:
>> Can anyone confirm successful use of connectionBacklog for the smtp
>> service on james 3.0 beta4 (or any v3). Successful use of
>> connectionBacklog for any of the other services e.g. imap, lmtp and pop3
>> is also of interest as under the covers the code is all common.
>>
>> Firstly I gather the connectionBacklog setting is controlling the
>> backlog just as is done in
>> http://docs.oracle.com/javase/6/docs/api/java/net/ServerSocket.html
>>
>> Secondly comparing the code
>>   -
>> http://svn.apache.org/repos/asf/james/protocols/trunk/netty/src/main/java/org/apache/james/protocols/netty/AbstractAsyncServer.java
>>
>>
>>   -
>> http://svn.apache.org/repos/asf/james/protocols/tags/protocols-1.6.2/netty/src/main/java/org/apache/james/protocols/netty/AbstractAsyncServer.java
>>
>>
>>
>> reports no differences so apart from the different versions of netty
>> between beta4 and where beta5 development is there should be no
>> difference with the backlog between beta4 and the current development
>> stream.
>>
>>
>> Changing the connectionBacklog value does cause the startup log entry
>> (SMTP Service connection backlog is: XXX) to change accordingly,
>> however...
>>
>> SETUP
>> -----
>>
>> connectionBacklog = 1
>> connectionLimit = 1
>>
>> TESTING
>> -------
>>
>> With two command lines, use telnet to connect to the smtp service, the
>> first telnet instance will establish a connection.
>>
>> The second instance reports back immediately that a connection can not
>> be established, whereas I would expect the second instance to hang and
>> either establish a connection when the first telnet instance disconnects
>> or a timeout occurs.
>>
>>
>> Testing thus far has not been in a controlled environment so the backlog
>> issue may well not be with james, but before I go much further I wanted
>> to see what anyone else out there is seeing.
>>
>> Thanks
>> Phillip
>>
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