Luis Lopez created NUTCH-1821:
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Summary: Nutch Crawl class for EMR
Key: NUTCH-1821
URL: https://issues.apache.org/jira/browse/NUTCH-1821
Project: Nutch
Issue Type: Wish
Affects Versions: 1.6
Environment: Amazon EMR
Reporter: Luis Lopez
Hi all,
Some of us are using Amazon EMR to deploy/run Nutch and from what I've been
reading in the users mailing list there are 2 common issues people run into...
first, EMR supports up to Hadoop 1.0.3 (which is kind of old) and second, from
Nutch 1.8+ the Crawl class has been deprecated.
The first issue poses a problem when we try to deploy recent Nutch versions.
The most recent version that is supported by EMR is 1.6, the second issue is
that EMR receives a jar and main class to do its job and from 1.8 the Crawl
class has been removed.
After some tests we completed a branch (from Nutch 1.6 + Hadoop 1.0.3) that
improves the old Crawl class so it scales, since 1.6 is an old version I wonder
how can we contribute back to those that need to use ElasticMapreduce.
The things we did are:
a) Add num fetchers as a parameter to the Crawl class.
For some reason the generator was always defaulting to one list( see:
http://stackoverflow.com/questions/10264183/why-does-nutch-only-run-the-fetch-step-on-one-hadoop-node-when-the-cluster-has)
creating just one fetch map task... with the new parameter we can adjust the
map tasks to fit the cluster size.
b) Index documents on each Crawl cycle and not at the end.
We had performance/memory issues when we tried to index all the documents
when the whole crawl is done, we moved the index part into the main Crawl cycle.
c) We added an option to delete segments after their content is indexed into
Solr. It saves HDF space since the EC2 instances we use don't have a lot of
space.
So far these fixes have allowed us to scale out Nutch be efficient with Amazon
EMR clusters. If you guys think that there is some value on these changes we
can submit a patch file.
Luis.
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