1. Runtime compilation and
code execution in groovy

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S o f t w a r e E n g i n e e r a t E P A M
R a m a n M a s k a l e n k a

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Disclaimer

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Problem statement

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Problem statement

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When can we use it
A S A P R OX Y S E R V I C E W I T H T R A N S F O R M E R

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When can we use it
A S A C O M P L E X DY N A M I C A L LY C A LC U L AT E D C O N F I G U R AT I O N

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How can we solve it?

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AWS Step Function

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AWS Step Function
Pros
• AWS is popular
• Different languages support
• Version control
• Source editor
• Lambdas be integrated with Amazon
Xray for tracing
Cons
• Lambdas can be costly if we have a
lot of scripts and high request load
• Appeared only in 2018

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How can we solve it?
JSR 199 (mvn-classloadr, jianimo)
Write your own compiler
JSR 223
Oracle Nashorn engine (Till Java 11)
JSR 223
ScriptEngineManager().getEngineByExt
ension("kts")

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How can we solve it?
GroovyClassLoader

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How does it work?
H I G H L E V E L F LO W

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How does it work?
S I M P L EST C O D E E X A M P L E

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How does it work?
S I M P L EST C O D E E X A M P L E

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How does it work?
DY N A M I C S C R I P T P R O P E R T I ES
• Script state clears between runs (For example script “def v; v = v ? v+1 : 1” will
return the same result during multiple executions)
• Binding variables are mutable and can be used to store/pass state (For example if
we have binding variable “v” and script “v = v+1” binding will be changed during
execution)
• Binding doesn’t create a copy of the passed map so it will be changed aswell
• Script code behaves the same as any other groovy code – you can use “import”
statements in it
• GroovyClassLoader will use your current thread class loader as parent by default,
but you can provide desired parent on your own

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Errors and stack trace
D E FAU LT

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Errors and stack trace
SA N I T I Z E D A P P R O AC H

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Servlet example

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Constant class loading?
Jmeter: 50 requests per second, 300 seconds
CATALINA_OPTS=-XX:MaxMetaspaceSize=100m

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Constant class loading issue
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Constant class loading issue

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Performance
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Software
• Jmeter script
• 50 requests per second
• Spf4j to record execution
• Win 10 x64
• Java 8 (1.8.0_151)
• Tomcat 8.5.24
Hardware
• Intel core i5-8600k
• 16 Gb OZU

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Performance Jmeter request
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Performance step 1 parse class max
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Performance step 1 parse class avg min
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Performance step 2 create script
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Performance step 3 run script max
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Performance step 3 run script avg-min
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Performance cleanup classes max
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Performance cleanup classes avg-min
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Performance jmeter endpoint summary
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Label # Samples
Avera
ge
Media
n
90%
Line
95%
Line
99%
Line Min Max Error %
Throughp
ut
Receiv
ed
KB/se
c
Sent
KB/se
c
RandomScript 29955 28 17 36 45 99 10 30790,000% 49.92/s8,40 81,86

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Pros and cons
Pros
• Reconfiguration on flight
• Works great as transaction
transformer
• Interactive development in runtime
• Almost zero time for deployment
Cons
• Reinventing Source control
• Hard to review
• High Security risks
• Self implemented testing
• Harder to monitor
• High risks of get fired in case of
production error caused by your
change
• More often Major GC
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