How to let Apache Nutch index the results via ElasticSearch over REST API.

In my work, we used Apache Nutch to fetch and parse some data from various websites. The data is pretty huge, so we need to index this on ElasticSearch. In my initial prototypes, I discovered that we can't use AWS ElasticSearch because AWS doesn't expose the native transport protocol; we can only talk to it via its RESTful API. In the official Nutch releases (v2.3.1 and v1.13, as of July 22, 2017), the plugin for ES doesn't support the RESTful API. When I checked the source code though, I was quite surprised that there's another plugin for this. Unfortunately, there's zero documentation on this, so I wish these notes would help others. Note: the URL regex config and HTTP options need to be set too, the IP addresses need to be whitelisted, etc... just leave a comment in case I miss something.

OS used for this experiment: Ubuntu 16.04.2 LTS

Install Java

add-apt-repository ppa:webupd8team/java

apt-get update

apt-get install oracle-java8-installer

Install ant

apt-get install ant

Increase the ulimit settings

(TODO: these settings should survive a reboot; just edit /etc/sysctl.conf or something)

ulimit  -f unlimited \

        -t unlimited \

        -v unlimited \

        -n 64000 \

        -m unlimited \

        -u 64000

Install Apache Nutch

Download the source code

git clone https://github.com/apache/nutch.git

Build

ant clean runtime

Put this inside runtime/local/config/nutch-site.xml:

<?xml version="1.0"?>

<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>




<configuration>

  <property>

    <name>http.agent.name</name>

    <value>Spiderman</value>

  </property>




  <property>

    <name>plugin.includes</name>

    <value>protocol-(http|httpclient)|urlfilter-regex|index-(basic|more)|query-(basic|site|url|lang)|indexer-elastic|indexer-elastic-rest|nutch-extensionpoints|parse-(text|html|msexcel|msword|mspowerpoint|pdf)|summary-basic|scoring-opic|urlnormalizer-(pass|regex|basic)|parse-(html|tika|metatags)|index-(basic|anchor|more|metadata)</value>

  </property>




  <property>

    <name>parser.character.encoding.default</name>

    <value>utf-8</value>

  </property>

  <property>

    <name>elastic.rest.host</name>

    <value>aws-elastic-search-endpoint.example.org</value>

  </property>




  <property>

    <name>elastic.rest.port</name>

    <value>443</value>

  </property>




  <property>

    <name>elastic.rest.index</name>

    <value>nutch</value>

  </property>




  <property>

    <name>elastic.rest.type</name>

    <value>doc</value>

  </property>




  <property>

    <name>elastic.rest.https</name>

    <value>true</value>

  </property>




  <property>

    <name>elastic.rest.trustallhostnames</name>

    <value>false</value>

  </property>




</configuration>

Make sure to whitelist your IP address first in AWS ElasticSearch’s policy settings. Yikes it's 7:11AM now... need to sleep. Hahaha... :p

Setting up Apache Nutch v2.3.1 on Ubuntu with MongoDB and ElasticSearch

These are my notes for installing Apache Nutch v2.3.1 on Ubuntu in my work. We'll probably not use Nutch 2.3 because AWS ElasticSearch doesn't support the native transport protocol (it only supports the REST API, and it exposes it in a non-standard manner on port 80); thus we'll have a hard time indexing the data unless we maintain the servers ourselves. We can probably use AWS CloudSearch, but Nutch 2.3 doesn't have a plugin for it, unlike Nutch 1.13.

Anyway, there are lots of similar HOWTOs out there, but this one points to specific versions and URLs so you can just copy and paste these to get your system up and running in a few minutes.

OS used for this experiment: Ubuntu 16.04.2 LTS

Make sure that Ubuntu is the latest version

apt-get update

apt-get dist-upgrade

reboot #if necessary

Updating to the latest version is needed to fix the glibc bug that affects MongoDB. It’s probably not required anymore, but it’s good to be safe.

Install Java

add-apt-repository ppa:webupd8team/java

apt-get update

apt-get install oracle-java8-installer

Install ant

apt-get install ant

Increase the ulimit settings

(TODO: these settings should survive a reboot)

ulimit  -f unlimited \

        -t unlimited \

        -v unlimited \

        -n 64000 \

        -m unlimited \

        -u 64000

Install MongoDB

apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 0C49F3730359A14518585931BC711F9BA15703C6




echo "deb [ arch=amd64,arm64 ] http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.4 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-3.4.list




apt-get update

apt-get install mongodb-org




service mongod start




echo "use nutch" | mongo

Install Apache Nutch

Download and extract

wget http://apache.cs.utah.edu/nutch/2.3.1/apache-nutch-2.3.1-src.tar.gz

tar xvf apache-nutch-2.3.1-src.tar.gz

Edit the configs

Uncomment this line at apache-nutch-2.3.1/ivy.xml:

<dependency org="org.apache.gora" name="gora-mongodb" rev="0.6.1" conf="*->default" />

Uncomment these lines at apache-nutch-2.3.1/runtime/local/conf/gora.properties:

gora.datastore.default=org.apache.gora.mongodb.store.MongoStore

gora.mongodb.override_hadoop_configuration=false

gora.mongodb.mapping.file=/gora-mongodb-mapping.xml

gora.mongodb.servers=localhost:27017

gora.mongodb.db=nutch

Build Apache Nutch

ant runtime #needs to be run in the top directory

Install ElasticSearch

Setup ElasticSearch on AWS

Create a new AWS ElasticSearch domain and whitelist the server(s) where Apache Nutch is installed. AWS ElasticSearch doesn’t support the native transport protocol (port 9300). We may be able to use AWS if Nutch supports the HTTP REST protocol. Needs more research.

Manual Installation

# It's possible to use the latest version, ES5, but you need to update the indexer.




wget -qO - https://packages.elastic.co/GPG-KEY-elasticsearch | sudo apt-key add -

echo "deb http://packages.elastic.co/elasticsearch/1.7/debian stable main" | sudo tee -a /etc/apt/sources.list.d/elasticsearch-1.7.list

apt-get update && sudo apt-get install elasticsearch

Edit /etc/elasticsearch/elasticsearch.yaml and put this:

network.host: 127.0.0.1

cluster.name: nutch

node.name: nutch1

Finish up

update-rc.d elasticsearch defaults

/etc/init.d/elasticsearch restart

Install Kibana (optional, didn't install this since curl works fine)

echo "deb http://packages.elastic.co/kibana/4.4/debian stable main" | sudo tee -a /etc/apt/sources.list.d/kibana-4.4.x.list




apt-get update && sudo apt-get install kibana

Put this inside apache-nutch-2.3.1/runtime/local/conf/nutch-site.xml

<?xml version="1.0"?>

<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>




<configuration>

  <property>

    <name>storage.data.store.class</name>

    <value>org.apache.gora.mongodb.store.MongoStore</value>

    <description>Default class for storing data</description>

  </property>




  <property>

    <name>http.agent.name</name>

    <value>Spiderman</value>

  </property>




  <property>

    <name>plugin.includes</name>

    <value>protocol-(http|httpclient)|urlfilter-regex|index-(basic|more)|query-(basic|site|url|lang)|indexer-elastic|nutch-extensionpoints|parse-(text|html|msexcel|msword|mspowerpoint|pdf)|summary-basic|scoring-opic|urlnormalizer-(pass|regex|basic)|parse-(html|tika|metatags)|index-(basic|anchor|more|metadata)</value>

  </property>

  <property>

    <name>elastic.host</name>

    <value>127.0.0.1</value>

  </property>




  <property>

    <name>elastic.port</name>

    <value>9300</value>

  </property>




  <property>

    <name>elastic.cluster</name>

    <value>nutch</value>

  </property>




  <property>

    <name>elastic.index</name>

    <value>nutch</value>

  </property>




  <property>

    <name>parser.character.encoding.default</name>

    <value>utf-8</value>

  </property>




  <property>

    <name>http.content.limit</name>

    <value>6553600</value>

  </property>




  <property>

    <name>elastic.max.bulk.docs</name>

    <value>2000</value>

  </property>




  <property>

    <name>elastic.max.bulk.size</name>

    <value>2500500</value>

  </property>




</configuration>

Automatically scaling and deploying Server Density agent on AWS Elastic Beanstalk

We're using AWS ElasticBeanstalk in one of our projects at my work. EB is an abstraction on top of Elastic Load Balancing and EC2 (which is yet another abstraction on top of Xen, but I digress hehe...), and I really appreciate how it simplifies a lot of routine sysad tasks. EB allows us to scale the website up and down, depending on the traffic.

One problem that we encountered during development was a memory leak from PHP.  To prevent another downtime (or at least help predict when the servers are about to go offline), I decided to use Server Density to implement an early warning system that would give us a heads up when the server's memory is about to run out. Server Density is a pretty great service. We've been using it for quite some time now. Server Density works by letting you install an agent inside of your servers, and the agent will then continuously push metrics to their server. Server Density then collects all these logs and displays them into nice graphs. If a metric crosses the threshold in one of your conditions (i.e., if the CPU load is >= 90% or disk space is <= 5GB), Server Density then sends you notification via e-mail, SMS, and Slack.

The Server Density agent can be installed during each EB deployment by executing this inside your deployment script at .ebextensions/:

curl https://archive.serverdensity.com/agent-install.sh | bash -s -- -a ACCOUNTNAME -t PUTYOURKEYHERE -g GroupNameForYourEB -p amazon -i

Determining the amount of free memory in Linux is somewhat tricky. I can't use the memory usage metric to trigger a notification because Linux always shows that nearly all of the memory is being used, even though in reality they're just being used as cache. To get a more reliable metric, I used swap space instead. The theory is that the instances are supposed to have enough RAM for the tasks; when memory runs out, Linux uses the swap space as a last resort. Thus, we can check if swap space is >= 1MB to trigger a notification.

Next problem: since EB regularly deploys and terminates the instances, Server Density ends up monitoring servers that no longer exist. We needed a way to automatically stop Server Density from monitoring instances that have been terminated.

Solution: I made a CloudWatch rule that triggers whenever instances are stopped or terminated. The events are then pushed to a Lambda function which calls Server Density's API to remove the monitoring.

Here's the architecture that I came up with:

I think CloudWatch has a way to monitor the swap space, but the last time I checked, AWS SNS (a separate AWS service that sends notifications) can't send SMS messages to Philippine numbers so I can't wake up (not joking, unfortunately haha) whenever there are server problems.

Update: Turns out that Linux' default swappiness value is 60, which means that it will use swap ahead of time even though around half (or 80%? the docs have conflicting calculations) of the RAM is still available. To avoid this situation, set the swappiness to 1. You can even set it to 0 if you want:

sysctl vm.swappiness=1