How To Install and Configure Riak2 with Python3 on Ubuntu 14.04

In this section, we will configure and launch a Riak node.

To start, we will need to optimize Riak’s Erlang VM with some recommended settings. We will make two modifications: setting queue scan intervals and disabling scheduler compaction of load.

Open the new Riak 2.0’s configuration file using nano or your favorite text editor.

sudo nano /etc/riak/riak.conf

Uncomment the erlang.schedulers.force_wakeup_interval = 500 line, highlighted below. Make sure that the leading space is also deleted, so that the e is the first character of the line.

. . .

## Set scheduler forced wakeup interval. All run queues will be
## scanned each Interval milliseconds. While there are sleeping
## schedulers in the system, one scheduler will be woken for each
...
## Default: 500
##
## Acceptable values:
##   - an integer
## erlang.schedulers.force_wakeup_interval = 500

. . .

Repeat this process for the erlang.schedulers.compaction_of_load = false in the block directly after:

. . .

## Enable or disable scheduler compaction of load. By default
## scheduler compaction of load is enabled. When enabled, load
## balancing will strive for a load distribution which causes as many
...
## Default: false
##
## Acceptable values:
##   - one of: true, false
## erlang.schedulers.compaction_of_load = false

. . .

Save and exit the file.

To start a Riak node, run:

sudo riak start

You will see the following.

!!!!
!!!! WARNING: ulimit -n is 1024; 65536 is the recommended minimum.
!!!!

The above message warns that our system has a low open file limit, which restricts the number of open file handles at any given moment. Think of each handle as a writing tool that we own. Every computer process requires a writing tool, to write

By default, the system’s limit on available writing tools is 1024; Riak recommends raising that limit to 65536. To raise this limit, see official Riak Open Files Limit documentation.

To double-check that your node is running, use the following.

sudo riak ping

The command will output pong if the node is running and will return an error otherwise.

To run a sequence of pre-built Riak tests, run:

sudo riak-admin test

This above command will output the following.

Successfully completed 1 read/write cycle to 'riak@127.0.0.1'

Your Riak node is now up and running.

The following is an optional series of steps that setup a sample Python-Riak application. The above instructions are language-agnostic and do not depend on the following to function normally. If you are not interested in a sample Python application, you can skip down to the Conclusion section.

First, check your current Python version.

python --version

You should see the output:

Output
Python 2.7.6

We would like to have python run Python 3. So, let’s remove the old binary.

sudo rm /usr/bin/python

Next, create a symbolic link to the Python 3 binary in its place.

sudo ln -s /usr/bin/python3 /usr/bin/python

If you run python --version again now, you’ll see the output Python 3.4.0.

Next, we will install Pip, the recommended package installer for Python packages. Pip allows us to easily manage any Python3 package we would like to have. For an overview of Pip, you can read out this tutorial.

To install it, simply run the following:

sudo apt-get install python3-pip

Now, we need to install the Python-Riak client. Several dependencies need to be satisfied first:

sudo apt-get install python3-dev libffi-dev libssl-dev

Install the client.

sudo pip3 install riak

Finally, we will code a sample application to test the Python-Riak combination. Create a new folder to house the application and create a new file in it.

mkdir ~/test
sudo nano ~/test/app.py

Paste the following inside. This is sample code from the official Riak documentation.

import riak

# connect to Riak
myClient = riak.RiakClient(pb_port=8087, protocol='pbc')

# create new Bucket
myBucket = myClient.bucket('test')

# store key-value pairs
val1 = 1
key1 = myBucket.new('one', data=val1)
key1.store()

val2 = "two"
key2 = myBucket.new('two', data=val2)
key2.store()

val3 = {"myValue": 3}
key3 = myBucket.new('three', data=val3)
key3.store()

# fetch the data
fetched1 = myBucket.get('one')
fetched2 = myBucket.get('two')
fetched3 = myBucket.get('three')

print('Value 1 correct: '+str(val1 == fetched1.data))
print('Value 2 correct: '+str(val2 == fetched2.data))
print('Value 3 correct: '+str(val3 == fetched3.data))

Now, run the following to test this application.

python ~/test/app.py

It will output the following warning, but this can be disregarded.

Python application warning
/usr/local/lib/python3.4/dist-packages/riak/security.py:54: UserWarning: Found OpenSSL 1.0.1f 6 Jan 2014 version, but expected at least OpenSSL 1.0.1g.  Security may not support TLS 1.2.
  warnings.warn(msg, UserWarning)

Transport Layer Security (TLS) 1.2 simply a tighter security protocol built on top of TLS 1.1, and TLS in turn is generally an upgrade from SSL. However, Internet Explorer does not universally support TLS 1.1 and 1.2, and TLS 1.2 is disabled in early versions of all popular browsers. As a consequence, we can settle for SSL to govern connections between the application and the Riak datastore safely.

It should output the following:

Value 1 correct: True
Value 2 correct: True
Value 3 correct: True

That’s it!

##Conclusion

You have now configured Riak 2 and successfully connected it to Python3. This Riak 2 installation is not specific to Python, however, and may be easily adapted to other languages. For more information on securing Riak, see official Riak 2 recommendations.