[jira] [Comment Edited] (NUTCH-2549) protocol-http does not behave the same as browsers

["Gerard Bouchar (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/NUTCH-2549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16430591#comment-16430591 ] 

Gerard Bouchar edited comment on NUTCH-2549 at 4/9/18 2:22 PM:
---------------------------------------------------------------

Hello,

  OK, I am going to open sub-tasks.

   As for the rewrite, I think it is very much needed. The bugs I reported here are the ones I could find, but I am sure there are more subtle bugs. HTTP is not as simple a protocol as one might think, and mixing low-level socket-related concerns with higher-level fetch logic related concerns can only lead to bugs.

  I do not think the content should be skipped in case of 404 or other errors, I was talking about redirects only. I do not see a case where the contents of a redirection page could be of interest, but your idea of adding a setting (disabled by default) for parsing it anyway should satisfy everyone.

 


was (Author: gbouchar):
Hello,

  OK, I am going to open sub-tasks.

   As for the rewrite, I think it is very much needed. The bugs I reported here are the one I could find, but I am sure there are more subtle bugs. HTTP is not as simple a protocol as one might think, and mixing low-level socket-related concerns with higher-level fetch logic related concerns can only lead to bugs.

  I do not think the content should be skipped in case of 404 or other errors, I was talking about redirects only. I do not see a case where the contents of a redirection page could be of interest, but your idea of adding a setting (disabled by default) for parsing it anyway should satisfy everyone.

 

> protocol-http does not behave the same as browsers
> --------------------------------------------------
>
>                 Key: NUTCH-2549
>                 URL: https://issues.apache.org/jira/browse/NUTCH-2549
>             Project: Nutch
>          Issue Type: Bug
>            Reporter: Gerard Bouchar
>            Priority: Major
>
> We identified the following issues in protocol-http (a plugin implementing the HTTP protocol):
>  * It fails if an url's path does not start with '/'
>  ** Example: [http://news.fx678.com?171|http://news.fx678.com/?171] (browsers correctly rewrite the url as [http://news.fx678.com/?171], while nutch tries to send an invalid HTTP request starting with *GET ?171 HTTP/1.0*.
>  * It advertises its requests as being HTTP/1.0, but sends an _Accept-Encoding_ request header, that is defined only in HTTP/1.1. This confuses some web servers
>  ** Example: [http://www.hansamanuals.com/main/english/none/theconf___987/manuals/version___82/hwconvindex.htm]
>  * If a server sends a redirection (3XX status code, with a Location header), protocol-http tries to parse the HTTP response body anyway. Thus, if an error occurs while decoding the body, the redirection is not followed and the information is lost. Browsers follow the redirection and close the socket soon as they can.
>  ** Example: [http://www.webarcelona.net/es/blog?page=2]
>  * Some servers invalidly send an HTTP body directly without a status line or headers. Browsers handle that, protocol-http doesn't:
>  ** Example: [https://app.unitymedia.de/]
>  * Some servers invalidly add colons after the HTTP status code in the status line (they can send _HTTP/1.1 404: Not found_ instead of _HTTP/1.1 404 Not found_ for instance). Browsers can handle that.
>  * Some servers invalidly send headers that span over multiple lines. In that case, browsers simply ignore the subsequent lines, but protocol-http throws an error, thus preventing us from fetching the contents of the page.
>  * There is no limit over the size of the HTTP headers it reads. A bogus server could send an infinite stream of different HTTP headers and cause the fetcher to go out of memory, or send the same HTTP header repeatedly and cause the fetcher to timeout.
>  * The same goes for the HTTP status line: no check is made concerning its size.
>  * While reading chunked content, if the content size becomes larger than {color:#9876aa}http{color}.getMaxContent(), instead of just stopping, it tries to read a new chunk before having read the previous one completely, resulting in a '{color:#333333}bad chunk length' error.{color}
> {color:#333333}Additionally (and that concerns protocol-httpclient as well), when reading http headers, for each header, the SpellCheckedMetadata class computes a Levenshtein distance between it and every  known header in the HttpHeaders interface. Not only is that slow, non-standard, and non-conform to browsers' behavior, but it also causes bugs and prevents us from accessing the real headers sent by the HTTP server.{color}
>  * {color:#333333}Example: [http://www.taz.de/!443358/] . The server sends a *Client-Transfer-Encoding: chunked* header, but SpellCheckedMetadata corrects it to *Transfer-Encoding: chunked*. Then, HttpResponse (in protocol-http) tries to read the HTTP body as chunked, whereas it is not.{color}
>  



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