onyx-seq

Onyx plugin for reading from a seq. The seq will be read from in way that is approriate for use with lazy-seqs. Therefore, this plugin can be useful for use with datomic.api/datoms calls, slow lazy calculations, line-seq / buffered reading, etc.

Build Status

Installation

In your project file:

[onyx-seq "0.7.0.0"]

(:require [onyx.plugin.seq])

Functions

sample-entry

Catalog entry:

{:onyx/name :entry-name
 :onyx/plugin :onyx.plugin.seq-input/input
 :onyx/type :input
 :onyx/medium :seq
 :seq/elements-per-segment 2
 :seq/checkpoint? true
 :onyx/batch-size batch-size
 :onyx/max-peers 1
 :onyx/doc "Reads segments from seq"}

Lifecycle entry:

[{:lifecycle/task :in
  :lifecycle/calls :onyx.plugin.seq-input/reader-calls}]

Checkpointing

onyx-seq will checkpoint the state of the read results. In the case of a virtual peer crash, the new virtual peer will drop from the seq until it has reached the first non fully acked segment. In order for this process to work, the seq that is read from must be reproducible on restart. If it is not, please disable checkpointing via :seq/checkpoint?.

Example Use - Buffered Line Reader

(defn inject-in-reader [event lifecycle]
  (let [rdr (FileReader. (:buffered-reader/filename lifecycle))] 
    {:seq/rdr rdr
     :seq/seq (line-seq (BufferedReader. rdr))}))

(defn close-reader [event lifecycle]
  (.close (:seq/rdr event)))

(def in-calls
  {:lifecycle/before-task-start inject-in-reader
   :lifecycle/after-task-stop close-reader})

;; lifecycles

(def lifecycles
  [{:lifecycle/task :in
    :buffered-reader/filename "resources/lines.txt"
    :lifecycle/calls ::in-calls}
   {:lifecycle/task :in
    :lifecycle/calls :onyx.plugin.seq-input/reader-calls}])

Attributes

key	type	description
:seq/elements-per-segment	integer	The number of elements to compress into a single segment

Contributing

Pull requests into the master branch are welcomed.

License

Copyright © 2015 Distributed Masonry LLC

Distributed under the Eclipse Public License, the same as Clojure.