I'm using Zach Tellman's excellent Manifold library, though I admit I don't
fully understand it.
My code queries a MySQL database and then needs to do some processing on
each row retrieved. I copy-and-pasted some code from the documentation for
Manifold:
;; 2017-07-10 -- we want a thread pool. I'm arbitrarily choosing 200
threads.
;; query_database/start will pull data from the database and dump it onto a
;; stream below, at which point each row should be assigned to one of the
rows
;; on our thread pool.
(def executor (me/fixed-thread-executor 200))
(defn enqueue
[sequence-from-database]
(slingshot/try+
(println "the type of the object from the database: " (type
sequence-from-database))
(->> (ms/->source sequence-from-database)
(ms/onto executor)
(ms/map api/query))
(catch Object o
(println " message queue is not happy about the message we were given")
(errors/error o "" " we tried to put something on the message queue,
but we got an error "))))
The line where I print out the type assures that I'm dealing with a LazySeq.
The code prints out the type and the first row:
the type of the object from the database: clojure.lang.LazySeq
in query_api/query {:profile_id 2, :profile_name Mike Shaw Automotive
Group, :headquarters_addr1 90 Madison St., :headquarters_city Denver,
:headquarters_state_code CO, :headquarters_country_code US, :url
mikeshawauto.com}
and then it stops. I assume there must be an Exception or Error happening,
but I can't find it. I've added as many general Catch clauses as I could:
(defn query
[row & args]
(println " in query_api/query " row)
(let [config (if args
(first args))
]
;; 2017-03-30 -- the API is overwhelmed and all I get is Socket Timeout
errors
(Thread/sleep 300)
(slingshot/try+
(call-api row)
(catch Object o
(println " error : " o)
;;(errors/error o row " we tried to call-api, but we got this error
")
)
(catch Error e
(println " there Error: " e))
)))
So if I do:
java -jar scan-database-find-similar-items-standalone.jar
The code runs till it prints out the first row from the database, and then
it stops. Nothing else happens. There are no error messages.
What did I miss?
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