LudoTheHUN / datasplash

Clojure API for a more dynamic Google Dataflow

Datasplash

Clojure API for a more dynamic Google Cloud Dataflow.

Usage

For now, you can consult the API docs.

You can also see ports of the official Dataflow examples in the datasplash.examples namespace.

Here is the classic word count:

(ns datasplash.examples
  (:require [clojure.string :as str]
            [datasplash.api :as ds])
  (:gen-class))

(defn tokenize
  [l]
  (remove empty? (.split (str/trim l) "[^a-zA-Z']+")))

(ds/defoptions WordCountOptions
  {:input {:type String
           :default "gs://dataflow-samples/shakespeare/kinglear.txt"
           :description "Path of the file to read from"}
   :output {:type String
            :default "kinglear-freqs.txt"
            :description "Path of the file to write to"}
   :numShards {:type Long
               :description "Number of output shards (0 if the system should choose automatically)"
               :default 0}})
               
(def format-count (fn [[k v]] (format "%s: %d" k v)))

(defn -main
  [str-args]
  (let [p (ds/make-pipeline 'WordCountOptions str-args)
        {:keys [input output numShards]} (ds/get-pipeline-configuration p)]
    (->> p
         (ds/read-text-file input {:name "King-Lear"})
         (ds/mapcat tokenize {:name :tokenize})
         (ds/frequencies)
         (ds/map format-count {:name :format-count})
         (ds/write-text-file output {:num-shards numShards})
         (ds/run-pipeline))))
         
;; example call:
;; (-main (into-array ["--input=./in.txt" "--output=./out.txt"]))

Run it locally with:

lein run word-count --input=in.txt --output=out.txt

Run in on Google Cloud (if you have done a gcloud init on this machine):

lein run word-count --input=gs://dataflow-samples/shakespeare/kinglear.txt --output=gs://my-project-tmp/results.txt  --runner=BlockingDataflowPipelineRunner --project=my-project --stagingLocation=gs://my-project-staging

Check all options with:

lein run --help=BlockingDataflowPipelineOptions

Caveats

• Due to the way the code is loaded when running in distributed mode, you may get some exceptions about unbound vars, especially when using instances with a high number of cpu. They will not however cause the job to fail and are of no consequences. They are caused by the need to prep the Clojure runtime when loading the class files in remote instances and some tricky business with locks and require.
• If you have to write your own low-level ParDo objects (you shouldn't), wrap all your code in the safe-exec macro to avoid issues with unbound vars. Any good idea about finding a better way to do this would be greatly appreciated!
• If some of the UserCodeException as seen in the cloud UI are mangled and missing the relevant part of the Clojure source code, this is due to a bug with the way the sdk mangles stacktraces in Clojure. In this case look for ClojureRuntimeException in the logs to find the original unaltered stacktrace.

License

Copyright © 2015, 2016 Oscaro.com

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.