Problem Statement
Our application was getting huge surge of orders in small duration and at certain periods of the day only. To quanity further we were getting around 5000-6000 orders in a span of 30-45 mins, around 3 times in a day. Remaining time order volume was 100-300 orders in an hour. To tackle this load, number of app servers were increased from 4 to 8.
Issue
However the concern here was that this costly infrastructure was idle for most part of the day. Going by above stats, the servers were idle (usage much below capacity) for approx 70-80% of the time.
Solution
To optimize this we were asked to explore the option of Throttling.
Throttling: In software terms throttling is a process responsible for regulating the rate at which application is processing.
Behaviour of application order processing before implementing throttling: Our application works by exposing a REST webservice. Client systems send order xml to this WS and its put on a JMS queue for processing.
Apache Camel Throttling PoC
I began by segregating above behaviour into two different components/routes.
One camel route listened to REST WS and put requests in a folder (say inbox). Another camel route listened to requests coming into this folder and put in on JMS queue but only after being throttled by Camel Throttling. Camel provides an option to define number of requests that need to be picked in a given time interval thereby making sure that even if order volumes surge, only pre defined amount of requests make it to processing stage. Rest stay in file system waiting to be picked up.
Sample code below:
<camel:route>
<!-- Reading from REST url -->
<camel:from uri="<REST WS url>" />
<to
uri="file:data/inbox?fileName=${header.OrderNumber}-${header.OrderVersion}.xml"
pattern="InOut" />
</camel:route>
<camel:route>
<!-- Route to put message from folder to main queue -->
<camel:from uri="file:data/inbox" />
<!-- Using camel provided throttling. Defined no of requests that can be processed in given time period -->
<throttle timePeriodMillis="60000">
<constant>1</constant>
<camel:log
message="Sucessfully processing service order ${headers.OrderNumber}-${headers.OrderVersion}.xml" />
<camel:to uri="file:data/outbox" />
</throttle>
</camel:route>
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