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https://issues.apache.org/jira/browse/NUTCH-475?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Doğacan Güney updated NUTCH-475:
--------------------------------

    Attachment: adaptive-delay_draft.patch

Patch with a simple adaptive algorithm. It measures the last response time of 
the server (say t), then waits at least k * t (where k, by default, is 10) 
before making a new request. There are also lower and upper bounds for the wait 
interval (so the fetcher will wait at least a predetermined value even if k * t 
is smaller than that).

Note that this is only a draft, and has some rough edges. It updates Fetcher2 
code(but not Fetcher code), so that one can benchmark it against regular 
Fetcher to see the difference.

> Adaptive crawl delay
> --------------------
>
>                 Key: NUTCH-475
>                 URL: https://issues.apache.org/jira/browse/NUTCH-475
>             Project: Nutch
>          Issue Type: Improvement
>          Components: fetcher
>            Reporter: Doğacan Güney
>             Fix For: 1.0.0
>
>         Attachments: adaptive-delay_draft.patch
>
>
> Current fetcher implementation waits a default interval before making another 
> request to the same server (if crawl-delay is not specified in robots.txt). 
> IMHO, an adaptive implementation will be better. If the server is under 
> little load and can server requests fast, then fetcher can ask for more pages 
> in a given interval. Similarly, if the server is suffering from heavy load, 
> fetcher can slow down(w.r.t that host), easing the load on the server.

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