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Merge pull request #11 from dacamo76/readme-long-polling-example

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Update README with long-polling usage example
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Chas Emerick 2014-09-13 07:30:15 -04:00
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@ -108,6 +108,28 @@ That's cleaner than having to interop directly with the Java SDK, but it's all
pretty pedestrian stuff. You can do more interesting things with some pretty pedestrian stuff. You can do more interesting things with some
simple higher-order functions and other nifty Clojure facilities. simple higher-order functions and other nifty Clojure facilities.
### Enabling SQS Long Polling
[Long polling](http://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-long-polling.html) reduces the number of empty responses by allowing Amazon SQS service to wait until a message is available in the queue before sending a response. You can enable long polling on an individual receive request by supplying the optional kwarg `:wait-time-seconds`:
:wait-time-seconds - time in seconds (bewteen 0 and 20) for SQS to wait if there are no messages in the queue. A value of 0 indicates no long polling.
```clojure
; ensure our queue is empty to start
#> (get (sqs/queue-attrs client q) "ApproximateNumberOfMessages")
"0"
#> (let [no-polling (future (sqs/receive client q))
long-polling (future (sqs/receive client q :wait-time-seconds 20))]
(Thread/sleep 10000) ;; Sleep 10s before sending message
(sqs/send client q "my message body")
(println (count @no-polling))
(println (count @long-polling)))
0
1
nil
```
### Sending and receiving Clojure values ### Sending and receiving Clojure values
SQS' message bodies are strings, so you can stuff anything in them that you can SQS' message bodies are strings, so you can stuff anything in them that you can