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The Harvester gem provides a simple interface where you can iterate your data source and send records to the sync engine. The default backend storage is Redis. Since the workers will use Resque which requires Redis, this make sense to use Redis to cache the data. However, any backend cache can be implemented.

I've now implemented using DynamoDB for the backend and SQS for the messages.

Your data sources are called "crops". You must assign a unique integer 1..100 to each crop. This is the integer that is used to create the Redis collection. By default Redis only allows a maximum of 16 databases, so this must be changed if you go above 16.

WARNING! Do not use crop number 1-9 in production, they are reserved for system testing.

The sync engine keeps a copy of your data source in a Redis databased indexed on the data source's primary key. When you sync your data, the engine uses this "cached" copy of the data to determine adds, deletes and changes. None of the data is inspected and the sync engine does not care what is in the data as long as it can be marshaled into a JSON string. The sync engine automatically does the conversion to and from JSON, so all you pass in is an object that responds to .to_json.


Add this line to your application's Gemfile:

gem 'barnyard_harvester'

And then execute:

$ bundle

Or install it yourself as:

$ gem install barnyard_harvester

Getting Started

This example assumes that you have Redis running on your local box localhost:6379. If you do not have Redis installed you can add :backend => :hash to the constructor.

require "barnyard_harvester"

# Get a connection to your data source
# (For this example we will use a YAML file)

@data = YAML::load_file("test.yml")

h = => false, :crop_number => 1,
                               #:backend => :hash
) do

  # Iterate your data here and call #process with the primary key and the value
  @data.each do |primary_key, value| "PK: #{primary_key}"
    h.process primary_key, value       # <<-- Send your data here!


puts h.stats

Sample output:

(0) adds, (0) deletes, (0) changes, (5) source records, (5) cache records


RSPEC is used to test this gem. Note that you should run each spec test individually. For some reason they confilict if run together. You will need Redis installed on the localhost:6379 or adjust the test accordingly.

This tests the initilization and parameters:

rspec -c spec/loader_spec.rb

Finished in 0.24556 seconds
7 examples, 0 failures

This tests the Redis backend of the harvester:

rspec -c spec/redis_rabbitmq_spec.rb

Finished in 0.27042 seconds
5 examples, 0 failures

This tests the Hash backend of the harvester:

rspec -c spec/hash_spec.rb

Finished in 0.06071 seconds
4 examples, 0 failures

Questions or Problems?


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request