Thank you for your suggestion. I have around 500+ internet urls
configured for crawling and crawl process is running in Amazon cloud.  I
have already reduced my depth to 8, topN to 1000 and also increased
fetcher threads to 150 and limited 50 urls per  host using
generate.max.per.host property. With this configuration Generate, Fetch,
Parse, Update completes in max 10 hrs. When comes to segment merge it
takes lot of time. As a temporary solution I am not doing the segment
merge and directly indexing the fetched segments. With this solution I
am able to finish the crawl process with in 24hrs. Now I am looking for
long term solution to optimize segment merge process.


-----Original Message-----
From: Susam Pal [mailto:susam....@gmail.com]
Sent: Monday, April 05, 2010 7:48 PM
To: nutch-user@lucene.apache.org
Subject: Re: Nutch segment merge is very slow

On Mon, Apr 5, 2010 at 5:27 PM, <ashokkumar.raveendi...@wipro.com>

> Hi
> I'm using Nutch crawler in my project and crawled more than 2GB of
> using Nutch runbot script. Up to 2GB segment merger has took and ended
> with in  24 hrs but now it takes more than 48 hrs and still running. I
> have set depth to 16 and topN to 2500. I want to run crawler every day
> as per my requirement.
> How to speed up segment merge and index process.
> Regards
> Ashokkumar.R

>From my experience of running Nutch on a single box to crawl a corporate
intranet with a depth as high as 16 and a topN value greater than 1000,
feel it isn't feasible to have one crawl per day.

One of these options might help you.

1. Run Nutch on a Hadoop cluster to distribute the job and speed up

2. Reduce the crawl depth to about 7, 8, or whatever works for you. This
means you wouldn't be crawling links discovered in the crawl perform at
depth 8. This may be a good or a bad thing for you depending on whether
want to crawl URLs found so deep in the crawl. These URLs may be obscure
less important because they are so many "hops" away from your seed URLs.
3. However, if the URLs found very deep are also important and you want
crawl them, you might have to sacrifice low ranking URLs by setting a
smaller topN value, say, 1000, or whatever works for you.

Susam Pal

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