Freshet

CQL based Clojure DSL for Apache Samza.

Freshet is the first step towards a complete implementation of Kappa Architecture based on extension to SQL [1] to sup- port continuous queries. Freshet implements a subset(select, windowing, aggregates) of CQL on top of Apache Samza. Freshet implements RStream and IStream relation-to-stream operators, tuple and time based sliding windows to convert streams to relations and basic relation to relation operators for implementing business logic. Following CQL, Freshet uses insert/delete stream to model instantaneous relations.

Freshet Query DSL

Defining Streams

(defstream wikipedia-feed
    (stream-fields [:title :string
                    :user :string
                    :diff-bytes :integer
                    :is-talk :boolean
                    :is-new :boolean
                    :is-bot-edit :boolean
                    :timestamp :long])
    (ts :timestamp))

SELECT Queries

(select wikipedia-feed
  (modifiers :istream)
  (window (unbounded))
  (where (> :diff-bytes 200)))

Freshet Query Execution (Based on CQL Execution Semantics)

docs/freshet-query-execution.png

License

Freshet is licensed under the Apache License, version 2.0

[1] Arvind Arasu, Shivnath Babu, and Jennifer Widom. 2006. The CQL continuous query language: semantic foundations and query execution. The VLDB Journal 15, 2 (June 2006), 121-142. DOI=10.1007/s00778-004-0147-z http://dx.doi.org/10.1007/s00778-004-0147-z