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@eslick eslick/gist:840823
Created Feb 23, 2011

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clojure-hadoop shuffle component example
;; Pseudocode example for guards in flows
(def *guard-time* [:days 7])
(defmacro with-resource-time-guard
[[name timespec inhibit?] &body ]
`(let [resource# (get-resource name)]
(cond (and ~inhibit? (resource-value resource#))
(resource-value resource#)
(or (resource-expired? resource# ~timespec)
(nil? (resource-value resource#)))
(let [new-value# (do ~@body)]
(set-resource! resource# new-value#)
new-value))))
(defmacro with-output-file
[[var output-file] & body]
(assert (symbol? var))
`(let [~var ~output-file]
~@body
~var))
(define-flow guarded-file-preprocessor [table outputBase inhibit-guard?]
(with-resource-time-guard ["MyResource" *guard-time* inhibit-guard?]
(with-output-file [dir (make-output-dir outputBase)]
(do-step file-preprocessor table dir))))
(define-flow major-flow [table output]
(do-step kmeans (guarded-file-preprocessor table *output-base* nil) output))
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