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(import 'java.text.SimpleDateFormat)
(let [lock (Object.)
date-format (SimpleDateFormat. "HH:mm:ss")]
(defn log [& msgs]
(locking lock
(apply println (str (.format date-format (java.util.Date.))) "-" (.getName (Thread/currentThread)) "-" msgs))))
;; This is just for logging the connection number
(def connections-created (atom 0))
(defn create-new-hbase-connection []
;;some side effecting code that creates a new socket
(Thread/sleep 1000)
(let [new-connection-number (swap! connections-created inc)]
(log "Connection created!" new-connection-number)
new-connection-number))
;;
(def global-hbase-connection (atom (delay (create-new-hbase-connection))))
(defn refresh-connection! []
(swap! global-hbase-connection
(fn [old-connection]
;; should close old connection
(log "Closing" @old-connection)
(delay (create-new-hbase-connection)))))
(defn run-with-hbase [f]
(try
(f @@global-hbase-connection)
(catch Exception _
(refresh-connection!)
(log "Retrying")
;; this retry logic is again a simplification
(run-with-hbase f))))
(dotimes [_ 4]
(future (run-with-hbase
(let [errored (atom false)]
(fn [connection]
(if @errored
(log "Using" connection)
(do
(log "Not happy with" connection)
(reset! errored true)
(throw (RuntimeException.)))))))))
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