Redtastic

Redtastic! Why? Because using Redis for analytics is fantastic!

Redtastic provides a interface for storing, retrieving, and aggregating time-intervalled data. Applications of Redtastic include developing snappy dashboards containing daily / weekly / monthly / yearly counts over time. Additionally Redtastic allows for the "mashing-up" of different statistics, allowing the drilling down of data into specific subgroups (such as "Number of unique customers who are also male, android users...etc").

Redtastic runs on Redis - so it's super fast.

$ gem install redtastic

or in your Gemfile

gem 'redtastic'

and run:

$ bundle install

Then initialize Redtastic in your application & connect it with a redis instance:

$redis = Redis.new
Redtastic::Connection.establish_connection($redis, 'namespace')

* specifying a namespace is optional and is used to avoid key collisions if multiple applications are using the same instance of Redis.

First, create a Redtastic Model:

class Checkins < Redtastic::Model
  type :counter
  resolution :days
end

The class must inherit from Redtastic::Model and provide some attributes:

• type: Required. The data type of the model. Valid values include:
  • :counter
  • :unique (more on types below).
• resolution: Optional. The degree of fidelity you would like to store this model at. Valid values include:
  • :days
  • :weeks
  • :months
  • :years
  • nil

* Note that methods requesting results at a higher resolution than that of the model will not work. Using a lower resolution will result in less memory utilization and will generally see faster query response times.

Incrementing / decrementing counters:

Checkins.increment(id: 1, timestamp: '2014-01-01')
Checkins.decrement(id: 1, timestamp: '2014-01-01')

Find a value of a counter for a single / day / week / month / year:

Checkins.find(id: 1, year: 2014, month: 1, day: 5)  # Day
Checkins.find(id: 1, year: 2014, week:  2)          # Week
Checkins.find(id: 1, year: 2014, month: 1)          # Month
Checkins.find(id: 1, year: 2014)                    # Year

Find the aggregate total over a dataspan:

Checkins.aggregate(id: 1, start_date: '2014-01-01', end_date: '2014-01-05')

Get the aggregate total + data points for each date at the specified interval:

Checkins.aggregate(id: 1, start_date: '2014-01-01', end_date: '2014-01-03', interval: :days)

An aggregation with the "interval" param specified returns the results in a hash:

{
  checkins: 5
  days: [
    {
      date: '2014-01-01',
      checkins: 2
    },
    {
      date: '2014-01-02',
      checkins: 1
    },
    {
      date: '2014-01-03',
      checkins: 1
    },
  ]
}

The above methods also have support for multiple ids.

Incrementing / decrementing multiple ids in one request:

Checkins.increment(id: [1001, 1002, 2003], timestamp: '2014-01-01')
Checkins.decrement(id: [1001, 1002, 2003], timestamp: '2014-01-01')

Find for mutiple ids at once:

Checkins.find(id: [1001, 1002, 2003], year: 2014, month: 1, day: 5)

Aggregations across mutiple ids can be quite powerful:

Checkins.aggregate(id: [1001, 1002, 2003], start_date: '2014-01-01', end_date: '2014-01-05')

As well as aggregating across mutiple ids w/ data points at the specified interval:

Checkins.aggregate(id: [1001, 1002, 2003], start_date: '2013-01-01', end_date: '2014-01-05', interval: :days)

Counters are just what they appear to be - counters of things. Examples of using counters are shown in the previous two sections.

Unique counters are used when an event with the same unique_id should not be counted twice. A general example of this could be a counter for the number of unique users that visited a place. In this case the "id" parameter would represent the id of the place and the unique_id would be the users id.

Examples

Incrementing / Decrementing (adding / removing a unique_id from a set for a particular id / time):

Customers.increment(id: 1, timestamp: '2014-01-05', unique_id: 1000)
Customers.decrement(id: 1, timestamp: '2014-01-05', unique_id: 1000)

Find:

Customers.find(id: 1, year: 2014, month: 1, day: 5, unique_id: 1000) # Returns true or false

Find the aggregate total over a datespan (this would only return the unique aggregate total):

Customers.aggregate(id: 1, start_date: '2014-01-01', end_date: '2014-01-05')

Find the aggregate total + data points for each point at a specified interval (again, this returns not only the unique aggregate total, but also the unique total for each interval data point ~ being each day / week / month / year...etc)

Customers.aggregate(id: 1, start_date: '2014-01-01', end_date: '2014-01-05', interval: :days)

Unique counters also support querying mutiple ids. For example, we can find the unique aggregate totals across multiple ids by doing:

Customers.aggregate(id: [1,2,3], start_date: '2014-01-01', end_date: '2014-01-05', interval: :days)

Attributes are unique counters that are not associated with an id, and can be thought of as a type of "global" group. This can be mashed up with other unique counters that are associated with ids to give the same result as if they were associated with that id. The main advantages to using this technique are:

• Save a tremendous amount of memory by not storing this data, for ever resolution interval, for every id
• Easier to update / maintain / rebuilding data is much quicker ( instead of having to update at every interval / id, you can just update it once at the "global" level)

This is best explained with the example below.

Say you have a unique counter "Customers", and a unique couner "Males". Instead of storing them both at the id & daily level we can get the number of males / day / id with the following:

class Customers < Redtastic::Model
  type :unique
  resolution :days
end

class Males < Redtastic::Model
  type :unique
end

then to mash up Customers against Males, just use the attributes parameter:

Customers.aggregate(id: 1, start_date: '2014-01-01', end_date: '204-01-09', attrbiutes: [:males])

You can even mash up multiple attributes. Suppose I want to see all the customers who are Male and Android Users. First add the AndroidUsers class:

class AndroidUsers < Redtastic::Model
  type :unique
end

then just add that into the query:

Customers.aggregate(id: 1, start_date: '2014-01-01', end_date: '2014-01-09', attributes: [:males, :android_users])

and just like every other example, attributes can be used in aggregations accross multiple ids:

Customers.aggregate(id: [1,2,3], start_date: '2014-01-01', end_date: '2014-01-09', attributes: [:males, :android_users])

All the methods available to unique counters can be used for unique counters acting as global attributes, with a few simplifications. Obviously, if it does not have a resolution and is not associated with an id, then there is no need to pass those parameters into any of those.

For example, adding / removing a unique_id to a global attribute set:

Males.increment(unique_id: 1000)
Males.decrement(unique_id: 1000)

or seeing if a unique_id is in a global set:

Males.find(unique_id: 1000)

Redtastic also provides access to the Redtastic::ScriptManager class which it uses internally to pre-load & provide an interface to running Lua Scripts on Redis. Although it is used by Redtastic to run its own scripts, anybody can use it to run their own custom scripts defined in their application:

Create a script: ./lib/scripts/hello.lua

return 'hello'

Tell ScriptManager to pre-load your scripts (after initializing Redtastic)

Redtastic::ScriptManager.load_scripts('./lib/scripts')

Now you can easily use your script anywhere in your application:

puts Redtastic::ScriptManager.hello # prints 'hello'

with every script having the ability to accept parameters for the KEYS & ARGV arrays:

  keys = []
  argv = []
  Redtastic::ScriptManager.hello(keys, argv)

For memory optimization Redtastic uses the methods outlined on Redis's memory optimization page. More specifically, all counters are not stored as individual keys, but rather in "buckets" of 1000 as fields inside of a Redis hash.

For example, if I am incrementing the a counter called "Visits" for a place with id 40231, rather than storing that counter as a key called "visits:40231", the counter would instead be located in the 40th "visit bucket" (id / 1000) labeled as key "visits:40", at hash index "231" (id % 1000). Any other visit counters for places with the id 40xxx would be stored in this bucket. A visualization of what part of this hash would look like is shown below:

"visits:40" : { ... "231": 23, "232": "0", "233":"4" ... }

showing the visit counter values for businesses with ids: 40231, 40232, 40233.

Important: to take advantage of this optimization, make sure to set the hash-max-ziplist-entries config value for your Redis instance as shown below:

CONFIG SET hash-max-ziplist-entries 1000

This will allow Redis to properly optimize any hash that has less than or equal to 1000 entries.

For more information check out Instagram's blog entry on how they were able to use this technique.

Redtastic uses Lua scripts to perform procedures that under normal circumstances would require mutiple requests to Redis, and thus can greatly reduce the impact of network latency. In most cases, methods invoked on a Redtastic model only involve one call to Redis (with additional queries / aggregations being done inside a Lua script durring the same Redis call). It should be noted, as with the use of any Lua script on Redis, that caution should be taken as misuse can lead to long running scripts that will block other requests.

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

• Set elapsed expiration times for each resolution of a model (ie. keys of resolution days expire in 1 year, months expire in 2 years...etc).
• For large, multi-id aggregations, set batch size & do aggregations in serveral batches rather than all in one lua run to prevent long running lua scripts from blocking any other redis operations.
• Support for hourly resolutions