README

## Copyright (C) 2010, Paco Nathan. This work is licensed under 
## the BSD License. To view a copy of this license, visit:
##    http://creativecommons.org/licenses/BSD/
## or send a letter to:
##    Creative Commons, 171 Second Street, Suite 300
##    San Francisco, California, 94105, USA
##
## @author Paco Nathan <ceteri@gmail.com>


Slinky provides an open source, high-performance Web Crawler, plus
common Text Analytics, implemented in Python. 

  * uses Redis key/value store for both CrawlQueue and PageStore
  * uses SQLite to persist crawled URI content
  * uses Neo4j to persist and analyze URI metadata
  * uses Hadoop, R, Gephi for Text Analytics and Link Analytics

This leverages a "Particle Cluster" design pattern. In contrast to
MapReduce, a Particle Cluster is particularly well-suited for
combinging highly reliable servers plus low-cost/unreliable VMs. In
other words, you can take advantage of CPU + memory + I/O on availably
but relatively ephemeral resources -- which might get taken away
without notice. For example in AWS, the key/value store could run on a
large EC2 node, while the distributed tasks run on Spot Instances --
based on pricing and availability. This pattern helps maximize
throughput and reliability while minimizing the cost of scale-out for
long-running jobs.


Required installs for worker nodes:

	http://github.com/andymccurdy/redis-py
	http://www.crummy.com/software/BeautifulSoup/
	http://components.neo4j.org/neo4j.py/
	http://jpype.sourceforge.net/
	http://henry.precheur.org/python/rfc3339 (already included)

Additional required installs for server nodes:

	http://code.google.com/p/redis/downloads
	http://www.sqlite.org/download.html
	http://neo4j.org/download/

Usage:
	# initialize Redis; run on server node...
	cd PATH_TO_REDIS
	nohup ./redis-server &
	# you probably want to config so it does "BGSAVE"

	# edit "config.tsv" for your settings...
	# e.g., Slinky handles ~100 crawler threads/node, but not in default config

	# initialize CrawlQueue and PageStore; run from any node...
	./src/slinky.py redis_host:port:db flush
	./src/slinky.py redis_host:port:db config < config.tsv
	./src/slinky.py redis_host:port:db whitelist < whitelist.tsv
	./src/slinky.py redis_host:port:db seed < urls.tsv

	# perform a crawl; run this on each worker node...
	nohup ./src/slinky.py redis_host:port:db perform &
	# will poll/sleep indefinitely; use "kill -9 PID" to terminate

	# persist the crawled URI content; run from any reliable node with attached storage...
	nohup ./src/slinky.py redis_host:port:db persist &
	# will poll/sleep indefinitely; use "kill -2 PID" to close with no data loss

	# analyze the crawled URI metadata; run from any reliable node with attached storage...
	nohup ./src/slinky.py redis_host:port:db analyze &
	# will poll/sleep indefinitely; use "kill -2 PID" to close with no data loss