Thanks Oleg. This will help for new connections getting created to pick up the 
new IP. But, how can we manage connections that were established and exist in 
the pool when the DC switch is made? . I saw that connectionmanger shutdown() 
will close all connections, but that would also make it and the HttpClients 
unusable unless they are initialized again. Is there any way to just flush all 
existing connections?

-Joseph

-----Original Message-----
From: Oleg Kalnichevski [mailto:ol...@apache.org] 
Sent: Tuesday, March 04, 2014 8:14 AM
To: HttpClient User Discussion
Subject: Re: Connection Pool and DNS Resolution timeout

On Mon, 2014-03-03 at 12:59 +0000, Alex, Joseph (Contractor) wrote:
> Hi,
> 
> We use HttpClient 3.1 and Httpcomponents 4.2.x in some of our apps with 
> MultiThreadedHttpConnectionManager and PoolingClientConnectionManager 
> respectively. Some of our server endpoints use a Global Name which can be 
> switched to point to different data centers at runtime, depending on which 
> one is active (with the other DC still being "alive"). Example 
> www.global.com<http://www.global.com> which could either point to 
> www.dc1.com<http://www.dc1.com> or www.dc2.com<http://www.dc2.com>. When this 
> switch was done, we noticed that the connections were not picking up the new 
> DC's IP and still routing to the old one. Assuming that the DNS resolution 
> timeouts (networkaddress.cache.ttl) is set to a low value in the JVM, would 
> the connection pool honor this value and reset the connections accordingly? . 
> If they don't, what options do we have of ensuring that the connections are 
> reset, and recreated with the new DNS resolution, without having to restart 
> the JVM?
> 
> Thanks,
> Joseph

Hi Joseph

HttpClient of all versions are fully reliant on the standard DNS resolution 
mechanism provided by JRE. They also do not attempt to cache or re-use resolved 
addresses, so 'networkaddress.cache.ttl' parameter should have effect. 

Since HttpClient 4.2 though, one can plug in a custom DNS resolver 
implementation [1] to replace or enhance the standard resolution mechanism. 

Hope this helps

Oleg

[1]
http://hc.apache.org/httpcomponents-client-4.3.x/httpclient/apidocs/org/apache/http/conn/DnsResolver.html




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