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From Oleg Kalnichevski <ol...@apache.org>
Subject Re: Proxy Failover
Date Fri, 24 Apr 2015 13:49:31 GMT
On Fri, 2015-04-24 at 13:08 +0000, Mark A. Claassen wrote:
> Thank you.  I did see this, but saw that is was never finished.
> 
> I looked into the RetryHandler first, but wasn't sure if that was where to put it.  It
seemed the RetryHandler stuff was not intended to work on non-idempotent operations.  That
is why I tried to do this in the RoutePlanner, since it would clear that no request entities
had yet been sent.  (Eventually, I will want to send POST requests through the proxy.)
> 

It will not be very elegant but one probably could have RetryHandler and
RoutePlanner share state through HttpContext and make RetryHandler
'black-list' proxies upon failure instead of RetryHandler probing good
proxies.

Oleg 


> Mark Claassen
> Senior Software Engineer
> 
> Donnell Systems, Inc.
> 130 South Main Street
> Leighton Plaza Suite 375
> South Bend, IN  46601
> E-mail: mailto:mclaassen@ocie.net
> Voice: (574)232-3784
> Fax: (574)232-4014
>   
> 
> -----Original Message-----
> From: Oleg Kalnichevski [mailto:olegk@apache.org] 
> Sent: Friday, April 24, 2015 6:39 AM
> To: HttpClient User Discussion
> Subject: Re: Proxy Failover
> 
> On Thu, 2015-04-23 at 16:45 +0000, Mark A. Claassen wrote:
> > I found some information on proxy failover and HttpClient, but not much.  I was
wondering, though, if my approach is OK.  I realize there are inefficiencies, but before I
go there, I want to know if I am even on the right track.
> > 
> > I extended DefautRoutePlanner and implemented the determineProxy method.
> > In that method I get the list of potential proxies and then test them.  
> > I return the first one in the list that works. (Also, when I find one 
> > that works, I remember it so I don't need to test it again.)
> > 
> > In my constructor for my route planner, I create a separate HttpClient instance
that just uses the DefaultRoutePlanner, which returns NULL for determineProxy().
> > 
> > Has anyone done anything like this?
> > 
> > Thanks,
> > Mark
> > 
> > 
> > 
> > 	private boolean testProxy(URI targetURI, Proxy proxy) {
> > 			boolean rval;
> > 			if (proxy.type() != Proxy.Type.DIRECT) {
> > 				InetSocketAddress address = (InetSocketAddress) proxy.address();
> > 				HttpHost host = new HttpHost(address.getHostName(), 
> > address.getPort(), ApacheNetworkImpl.SCHEME_HTTP);
> > 
> > 				try {
> > 					URI uri = new URI(host.toURI());
> > 					RequestBuilder rb = RequestBuilder.get(uri);
> > 					HttpUriRequest request = rb.build();
> > 					try {
> > 						HttpResponse resp = testClient.execute(request);
> > 						rval = true;
> > 					}
> > 					catch (IOException ex) {
> > 						rval = false;
> > 						connectFailed(targetURI, address, ex);
> > 					}
> > 					finally {
> > 						request.abort();
> > 					}
> > 				}
> > 				catch (URISyntaxException ex) {
> > 					rval = false;
> > 				}
> > 			}
> > 			else
> > 				rval = true;
> > 			return rval;
> > 		}
> > 
> 
> Mark,
> 
> There is a JIRA for similar feature request
> 
> https://issues.apache.org/jira/browse/HTTPCLIENT-1176
> 
> It should be possible to come with a more efficient solution by using a custom HttpRequestRetryHandler
in additional to a custom RoutePlanner.
> 
> Hope this helps
> 
> Oleg
> 
> 
> 
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