Posts Tagged ‘python’

Fast to Lucene Solr: Choosing a Document Processing Pipeline for Solr

by Karen Lynn

One of the most powerful features of FAST ESP is its flexible document processing engine. The engine that ships with FAST ESP supports multiple document processing pipelines that comprise of multiple document processing stages. A document processing stage performs a document processing task and can add, modify or remove elements from a document before it is passed to the next stage in the pipeline. A simple example of processing stage would be one that processes a document’s URL element, ESP ships with many processing stages and several processing pipelines out of the box for handling both structured and unstructured documents. FAST ESP document processing engine also provides a Python plugin API to allow customers to create custom processing stages of their own, which is a feature we use heavily for our customer ESP installations.

Unfortunately, Solr does not offer the same robust support for document processing pipelines that ESP does. The ESP processing pipeline is document-centric while the Lucene Solr platform is field-centric. When a document is fed to ESP for processing, it is routed to processing stages in a processing pipeline that can access document elements generated by previous processing stages. This allows for complex and optimal operations that can leverage previous processing, such as reuse of a previously generated HTML DOM tree structures. When a document is passed to a Solr update handler, the document is broken up into a set of individual fields. Each field can have a set of processors known as Solr Analysis Filter that can be chained together for field processing before indexing occurs. While this is fine for content that has been heavily processed before being sent to Solr, individual filters lack the same level of access to other documents elements to easily support more complex processing behaviors.

Another difference between ESP and Solr platforms is that ESP’s document processing architecture allows it to be scaled independently from its indexing architecture. ESP’s document processing architecture is fully decoupled from its indexing architecture and is designed out-of-the-box to take advantage of multiple processor cores per machine and multiple document processor machines per cluster. Solr’s out-of-the-box document processing architecture is tightly coupled with its indexing architecture, making it difficult to independently scale Solr’s content processing capacity without adding the complexity and overhead of additional Solr services and Lucene indexes. When we work with multiple terabyte document sets, we find content processing tends to be the biggest bottleneck, so being able to scale content processing ability separately from indexing is mission critical.

If we want to leverage the power that Solr offers, but we need support for a more robust document processing framework, what are our options? There are quite a number of content processing frameworks we can chose from that we discovered during the course of our research. Some of the options currently available include, but are not limited to OpenPipeline OpenPipe, Pypes, UIMA, SMILA , Apache Commons Pipeline, Piped, Behemoth, and Cascading.

Most of these frameworks are written in Java which gives them access to an incredibly broad and diverse spectrum of Java libraries. Since Solr and Lucene are also written in Java, it might make a lot of sense to favor a Java processing framework from scratch, especially if you are more comfortable with Java as a programming language.

Since our clients tend to have highly customized document processing pipelines with many custom FAST ESP Python processing stages, we are heavily biased towards choosing a framework that minimizes the amount of code that would need to be migrated. Many of the available processing frameworks are written in Java, which would be fine if you prefer using Java and don’t have a large amount of currently working Python code to migrate. For our use cases, the decision of which framework to chose was incredibly simple given the option, so we chose Pypes for our migration solution.

For a full report on how we use Pypes for a Document Processing Engine including sample code, sign up for our free FAST to Lucene Solr White Paper here.

How to Index a Site with Python Using solrpy and a Sitemap

by Jeff Peck

If you are looking for a fast and easy way to populate a Solr instance using Python, read on.

The script provided here is a basic starting point to building the Solr index for any website with a sitemap, within minutes.  Simply modify the script to use your Solr instance and run with a path to your valid XML sitemap and it will begin populating your Solr index.

While you certainly can modify this script to fit your specific needs, you may even find that this script satisfies your Solr indexing requirements as-is.

To start, you need to be running Python 2.6 and have the following modules installed:

You can install these using easy_install or manually.

You will also require an Apache Solr instance.  (If you are looking for fully managed solution for hosting your Solr search application with a wide range of services, feel free to contact us.)

Ideally you will use this script on your own sitemap.  For detailed information on how to construct your sitemap click here: http://www.sitemaps.org/protocol.php.  You can search the web for other scripts that will automatically make sitemaps out of common CMS’s like WordPress and Joomla.  There are also sitemap generators available. You can also find a valid sitemap for testing here: http://www.google.com/sitemap.xml (~4Mb). We will assume that you have have a valid sitemap.

We will also assume that you have the default Solr schema.xml installed.

Write the following python script sitemap-indexer.py, replacing the value for solrUrl with the location of your own instance:

#! /usr/bin/env python
""" Index links from a sitemap to a SOLR instance"""

import sys
from BeautifulSoup import BeautifulSoup
import solr
import hashlib
import urllib2
from xml.etree.ElementTree import parse

# How many iterations max?  Enter 0 for no limit.
limit = 0 

# The URL of the solr instance
solrUrl = 'http://localhost:8080/sitemap-indexer-test'

# The xmlns for the sitemap schema
sitemaps_ns = 'http://www.sitemaps.org/schemas/sitemap/0.9'

if len(sys.argv) != 2:
	print 'Usage: ./sitemap-indexer.py path'
	sys.exit(1)

sitemapTree = parse(sys.argv[1])

solrInstance = solr.SolrConnection(solrUrl) # Solr Connection object

counter = 0
numAdded = 0

# Find all of the URLs in the form <url>...<loc>URL</loc>...</url>
for urlElem in sitemapTree.findall('{%s}url/{%s}loc'%(sitemaps_ns,sitemaps_ns)):
	counter = counter + 1 # Increment counter

	if limit > 0 and counter > limit:
		# For testing, if the limit is reached, break
		break;

	url = urlElem.text # Get the url text from the element

	try: # Try to get the page at url
		response = urllib2.urlopen(url)
	except:
		print "Error: Cannot get content from URL: "+url
		continue # Cannot get HTML.  Skip.

	try: # Try to parse the HTML of the page
		soup = BeautifulSoup(response.read())
	except:
		print "Error: Cannot parse HTML from URL: "+url
		continue # Cannot parse HTML.  Skip.

	if soup.html == None: # Check if there is an <html> tag
		print "Error: No HTML tag found at URL: "+url
		continue #No <html> tag.  Skip.

	try: # Try to set the title
		title = soup.html.head.title.string.decode("utf-8")
	except:
		print "Error: Could not parse title tag found at URL: "+url
		continue #Could not parse <title> tag.  Skip.

	try: # Try to set the body
		body = str(soup.html.body).decode("utf-8")
	except:
		print "Error: Could not parse body tag found at URL: "+url
		continue #Could not parse <body> tag.  Skip.

	# Get an md5 hash of the url for the unique id
	url_md5 = hashlib.md5(url).hexdigest()

	try: # Add to the Solr instance
		solrInstance.add(id=url_md5,url_s=url,text=body,title=body)
	except Exception as inst:
		print "Error adding URL: "+url
		print "\tWith Message: "+str(inst)
	else:
		print "Added Page \""+title+"\" with URL "+url
		numAdded = numAdded + 1

try: # Try to commit the additions
	solrInstance.commit()
except:
	print "Could not Commit Changes to Solr Instance - check logs"
else:
	print "Success. "+str(numAdded)+" documents added to index"

Make the script executable and run it:
./sitemap-indexer.py /path/to/sitemap.xml

It will start to go through the sitemap, parsing the content of each URL and if no errors found will add it to the Solr index. This process can take several minutes. There may be errors parsing many of the documents. They will simply be skipped, you may have to fine-tune the parser to fit your specific needs.

Once finished, it will output the number of documents that were committed to the Solr index.

You should be able to access your Solr Instance and run queries. There are numerous resources on the web to help you form query strings. There is also a query form in your Solr web admin interface that allows setting the various request parameters.

If you experience Solr Exceptions, check your Solr logs. If you modified your schema, be sure to reload your Solr instance as this may be the cause of Unrecognized Field Exceptions. You can find the default Solr schema in the example/solr/ directory of a new install of Solr.

If you would like to parse the documents for more specific tags than simply taking the entire body element (as this script does), refer to this documentation:
http://www.crummy.com/software/BeautifulSoup/documentation.html.

Integrate custom services with the Fast ESP Node Controller

by admin
Add your own services to ESP's Node Controller

Add your own services to ESP's Node Controller

Background

Integrating our own custom services with Fast ESP’s Node Controller provides us with several benefits:

  • Administrators without in-depth ESP knowledge can easily control services (e.g. start, stop, configure parameters)
  • Services can be started at boot time with the rest of ESP
  • espdeploy can be used to install our services in a multi-node cluster

The components required for this system are:

  1. The ESP Node Controller (with config file NodeConf.xml)
  2. The 3rd-party service (like a CherryPy server, log parser, etc.)
  3. A wrapper script (see below)

Steps for Integration

  1. Define the service you would like to integrate. It can be any script or binary that can be executed on the system. For example, the service might be a python script that takes command-line arguments and continues running itself (as is the case with a webserver).
  2. Create the wrapper script that sets up the proper environment and runs/stops the service properly. The wrapper script should be put in the $FASTSEARCH/bin directory (with executable permissions). Additionally, the wrapper script should pass $@ to your actual script so any/all arguments defined in $FASTSEARCH/etc/NodeConf.xml will be passed along properly from the Node Controller to your service. The following is an example of a wrapper script:
    #!/bin/sh
    
    # export the proper python path
    export PYTHONPATH=":/path/to/python"
    
    # run the script (backgrounded)
    python $FASTSEARCH/lib/python2.6/yourmodule/yourservice.py $@ &
    
    # determine the process id of the python script
    SCRIPT_PID="$!"
    
    # upon receiving a SIGTERM, forward it to the process
    trap "kill -TERM $SCRIPT_PID" SIGTERM
    
    # wait for SIGTERM from nctrl
    wait
  3. Define the service in $FASTSEARCH/etc/NodeConf.xml
    Add the following to the end of the <startorder> tag:
    <proc>servicename</proc>

    Add the following to the end of the <node> tag, customizing as appropriate:

    <!-- My Custom Service -->
    <process name="servicename" description="My Custom Service">
            <start>
                    <executable>binaryname</executable>
                    <parameters>-p 16940 -v</parameters>
                    <port base="4004"/>
            </start>
            <outfile>servicename.scrap</outfile>
    </process>
  4. Reload the Node Controller configuration with the following:
    nctrl reloadcfg

And that’s it!  Now you should be able to start, stop, configure, and deploy your services using Fast ESP tools.  Enjoy!