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From "Otis Gospodnetic (JIRA)" <>
Subject [jira] Commented: (NUTCH-629) Detect slow and timeout servers and drop their URLs
Date Mon, 14 Apr 2008 19:47:04 GMT


Otis Gospodnetic commented on NUTCH-629:

While the patch improves fetch speed when there are lots of timeouts, the "slow but not slow
enough" servers are still a problem.  By that, I mean servers whose download speed is over
the threshold, which stops them from just getting dropped from the fetch job, but slow enough
that, if they have a lot of URLs in the fetchlist, they still take longer to fetch from, and
thus draaaaaaag the fetch run out.

I *think* this download speed information has to be stored in the host DB (NUTCH-628).  Generator
could then use this information when generating the fetchlist.  For hosts that are slower,
it would generate fewer URLs, and for hosts that are faster, it could generate more URLs.
 In the ideal scenario, I think, this would result in URLs from all hosts getting fetched
around the same time.

Does this make sense?  Is my thinking OK or is it flawed?

> Detect slow and timeout servers and drop their URLs
> ---------------------------------------------------
>                 Key: NUTCH-629
>                 URL:
>             Project: Nutch
>          Issue Type: Improvement
>          Components: fetcher
>            Reporter: Otis Gospodnetic
>         Attachments: NUTCH-629.patch
> Fetch jobs will finish faster if we find a way to prevent servers that are either slow
or time out from slowing down the whole process.
> I'll attach a patch that counts per-server exceptions and timeouts and tracks download
speed per server.
> Queues/sservers that exceed timeout or download thresholds are marked as "tooManyErrors"
or "tooSlow".  Once they get marked as such, all of their subsequent URLs get dropped (i.e.
they do not fetched) and marked GONE.
> At the end of the fetch task, stats for each server processed are printed.
> Also, I believe the per-host/domain/TLD/etc. DB from NUTCH-628 would be the right place
to add server data collected by this patch.

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