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From "Sebastian Nagel (JIRA)" <>
Subject [jira] [Commented] (NUTCH-2451) MalformedURLExceptions on perfectly looking URLs?
Date Tue, 07 Nov 2017 12:01:00 GMT


Sebastian Nagel commented on NUTCH-2451:

Ok, after a look at the code ( it's during redirect handling. I didn't check the
Ftp spec but in HTTP redirects may absolute or relative. For the latter case it should be:
{{ u = new URL(u, response.getHeader("Location"));}} (within a try block to catch and log
the exception with URL and redirect location).

> MalformedURLExceptions on perfectly looking URLs?
> -------------------------------------------------
>                 Key: NUTCH-2451
>                 URL:
>             Project: Nutch
>          Issue Type: Bug
>          Components: protocol
>    Affects Versions: 1.13
>         Environment: Ubuntu 16.04.3 LTS
> OpenJDK 1.8.0_131
> nutch 1.14-SNAPSHOT
> Synology RS816
>            Reporter: Hiran Chaudhuri
> I tried running Nutch on my Synology NAS. As SMB protocol is not contained in Nutch,
I turned on FTP service on the NAS and configured Nutch to crawl ftp://nas.
> The experience gives me varying results which seem to point to problems within Nutch.
However this may need further evaluation.
> As some files could not be downloaded and I could not see a good error message I changed
the method org.apache.nutch.protocol.ftp.FTP.getProtocolOutput(Text, CrawlDatum) to not only
return protocol status but send the full exception and stack trace to the logs:
> {{    } catch (Exception e) {
>     	LOG.warn("Could not get {}", url, e);
>       return new ProtocolOutput(null, new ProtocolStatus(e));
>     }
> }}
> With this modification I suddenly see such messages in the logfile:
> {{2017-10-25 22:09:31,865 TRACE org.apache.nutch.protocol.ftp.Ftp - fetching ftp://nas/MediaPC/usr/lib32/gconv/
> 2017-10-25 22:09:32,147 WARN  org.apache.nutch.protocol.ftp.Ftp - Could not get ftp://nas/MediaPC/usr/lib32/gconv/
> 	at<init>(
> 	at<init>(
> 	at<init>(
> 	at org.apache.nutch.protocol.ftp.Ftp.getProtocolOutput(
> 	at
> Caused by: java.lang.NullPointerException
> }}
> Please mind the URL was not configured from me. Instead it was obtained by crawling my
NAS. Also the URL looks perfectly fine to me. Even if the file did not exist I would not expect
a MalformedURLException to occur. Even more, using Firefox and the same authentication data
on the same URL retrieves the file successfully.
> How come Nutch cannot get the file?

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