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https://issues.apache.org/jira/browse/HTTPCLIENT-852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12714443#action_12714443
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Oleg Kalnichevski commented on HTTPCLIENT-852:
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I examined the logs and that is what I have found so far:
The bug in HttpClient is triggered only when the redirect needs to be retried
for some reason, for instance, due to an I/O error. There appears to be a bug
Tinyproxy's connection management code causing a perfectly re-usable HTTP/1.1
connection to be dropped without proper notification of the client. The proxy
should have sent the 'Connection: close' if it was not going to re-use
HTTP/1.1connection). HttpClient assumes that the connection is still good,
executes the redirect on the same connection, which fails because the
connection has been closed on the proxy side. The second retry fails because
HttpClient mistakenly assumes the URI has already been visited.
While Tinyproxy's behavior is clearly broken, HttpClient should also be able to
deal with failed redirects and retry those correctly. The fix for this issue,
however, will require quite a bit of refactoring in the DefaultRequestDirector
and DefaultRedirectHandler and may take a few days to complete.
Oleg
> CircularRedirectException encountered when using a proxy, but not when
> reaching the target directly
> ---------------------------------------------------------------------------------------------------
>
> Key: HTTPCLIENT-852
> URL: https://issues.apache.org/jira/browse/HTTPCLIENT-852
> Project: HttpComponents HttpClient
> Issue Type: Bug
> Components: HttpClient, HttpConn
> Affects Versions: 4.0 Beta 2
> Environment: Proxy: tinyproxy/1.6.4
> Reporter: Charles Fr Rey
> Fix For: 4.0 Beta 3
>
> Attachments: withoutproxy.log, withproxy.log,
> withproxyALLOW_CIRC_RED.log
>
>
> A CircularRedirectException is encountered when using a proxy (tinyproxy on a
> remote machine), whereas everything is fine when using no proxy. The target
> is a URL such as http://www.seoconsultants.com/w3c/status-codes/301.asp which
> has a 301 redirection.
> The issue can be fixed by using ALLOW_CIRCULAR_REDIRECTS set to true (client
> params), but I can't consider this a "real" fix.
> Here is a snippet of code that exemplifies the problem (use your own proxy):
> ---
> String proxyHost = "xyz.webfactional.com";
> int proxyPort = 7295;
> DefaultHttpClient httpclient = new DefaultHttpClient();
> // without a proxy it's OK!
> httpclient.getParams().setParameter(ConnRoutePNames.DEFAULT_PROXY,
> new HttpHost(proxyHost, proxyPort, "http"));
> HttpParams params = httpclient.getParams();
> HttpClientParams.setRedirecting(params, true);
> HttpProtocolParams.setUserAgent(params,
> "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.0.10)
> Gecko/2009042315 Firefox/3.0.10");
> // OK, this fixes the problem, but at what cost / other problems ?
> //httpclient.getParams().setParameter(ClientPNames.ALLOW_CIRCULAR_REDIRECTS,
> true);
> String url = "http://www.seoconsultants.com/w3c/status-codes/301.asp";;
> HttpUriRequest request;
> HttpResponse response;
> request = new HttpGet(url);
> System.out.println("request = " + request.getRequestLine());
> response = httpclient.execute(request);
> System.out.println("status = " + response.getStatusLine());
> System.out.println("headers = " + Arrays.asList(response.getAllHeaders()));
> ---
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