Re: Problem using WebDetector in default-foreign-source.xml

Hi John,

    From what I can discern via a quick search of the code, WebDetector 
uses opennms/core/web/HttpClientWrapper.java which in turn uses the 
Apache HttpClient library, and this does appear to follow redirects by 
default.

Based on the examples shown on this blog 
http://www.baeldung.com/httpclient-stop-follow-redirect I can't see 
anywhere in OpenNMS's wrapper that disables or allows you to disable 
redirection.  I think this would be an ideal feature to have in a 
detector but I'm 50/50 on whether this is a bug or a feature request as 
following redirects is generally a reasonable thing for the detector to 
do. Either way I think you should probably raise is as an issue. 
Interestingly there's an old (and seemingly unresolved) issue that 
HttpMonitor doesn't follow redirects: 
https://issues.opennms.org/browse/NMS-5338

Based on this quick look, I reckon that the feature could be relatively 
easily implemented by adding a method to HttpClientWrapper which allows 
setting of a followRedirects boolean, and expose it via the WebDetector 
class too.

In this particular case, you could possible use HttpDetector instead but 
this only allows you to set maxRetCode which is a bit restrictive, but 
if you set it to 200 then there only appears to be four 1xx codes which 
are all a bit obscure; 
https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#1xx_Informational_responses

HTH

Jonathan


On 19/04/18 04:18, JohnD Blackburn wrote:
>
> Hi All,
>
> IÂ’ve come across an issue with setting up a web detector.
>
> IÂ’ve added the following to default-foreign-source.xml
>
> <detector name="RFINTEG-logcall" 
> class="org.opennms.netmgt.provision.detector.web.WebDetector">
>
> <parameter key="port" value="80"/>
>
> <parameter key="responseRange" value="200-200"/>
>
> <parameter key="timeout" value="10000"/>
>
> <parameter key="path" value="/cgi-bin/logcall.pl"/>
>
> </detector>
>
> And this is working and correctly detecting that URI on the server 
> that is supposed to be serving that.  However, there is another server 
> that automatically redirects all calls to non-existent URIÂ’s to 
> /users/signin/
>
> If I perform a curl on http://wrongserver/cgi-bin/logcall.pl I see the 
> return code of 302 with a reference to /users/signin/
>
> And of course running curl against http://wrongserver/users/signin/ is 
> giving a return code of 200.
>
> In the foreign source detector, I set the response range to only 
> accept 200 as valid code thinking that it would exclude the 302, but 
> it appears that the WebDetector is following the 302 redirect and 
> using the response code of the re-directed URI, so is therefore 
> incorrectly detecting this URI where it should not.
>
> How do I stop the detector from following the redirect, and only 
> detecting the URI if there is no re-direct?   In this case, if I get a 
> 302, then this is not the web server I am looking forÂ…
>
> Regards,
>
> John Blackburn
>
>
>
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