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https://issues.apache.org/jira/browse/GROOVY-7535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16011335#comment-16011335
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John Wagenleitner commented on GROOVY-7535:
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[~blackdrag] - as [~jkemnade] pointed out, there is a race condition between
threads when writing to the {{private static int categoriesInUse}} counter as
there is no guarantee that the values returned from calls to the Atomic will be
written in the same order. The scenario is:
1. T1 in {{endScope}} calls {{atomicCategoryUsageCounter.decrementAndGet()}}
and receives {{0}}
2. T2 in {{newScope}} calls {{atomicCategoryUsageCounter.incrementAndGet()}}
and receives {{1}}
3. T2 assigns {{categoriesInUse}} a value of {{1}}
4. T1 assigns {{categoriesInUse}} a value of {{0}}
5. Callsite called from T2 calls {{hasCategoryInCurrentThread}} and return is
{{false}}
The patch and PR both fix this by introducing ordering to the
{{atomicCategoryUsageCounter}} return value and the write to
{{categoriesInUse}}. Another way to fix without synchronizing would be to
remove the int counter and just use the AtomicInteger. However, my hunch is
that the int counter was retained because {{hasCategoryInCurrentThread}} is
probably called frequently so there might have been some performance concern
over requiring a method call and a volatile read that the AtomicInteger would
incur in order to implement the quick exit check for that method {{if
(categoriesInUse == 0) return false}}.
There is also a race between scopes in calls to
{{DefaultMetaClassInfo.setCategoryUsed}}, so I think it would also be good to
add those calls to the synchronized blocks if they are added.
> Groovy category throwing MissingMethodException and MissingPropertyException
> when using multiple threads
> --------------------------------------------------------------------------------------------------------
>
> Key: GROOVY-7535
> URL: https://issues.apache.org/jira/browse/GROOVY-7535
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 2.3.11, 2.4.4
> Environment: I have been able to reproduce this issue on a Cent O/S
> version 6.4 with Java 64 Bit JDK 1.8 and groovy 2.4.4.
> Reporter: James Oswald
> Assignee: Pascal Schumacher
> Fix For: 2.4.6
>
> Attachments:
> 0001-GROOVY-7535-fix-race-condition-between-the-modificat.patch,
> CategoryTest.groovy, exceptionForCategoryTest.txt,
> exceptionForTimeCategoryTest.txt, Test.groovy, TimeCategoryTest.groovy
>
>
> When using groovy use block, we randomly get
> groovy.lang.MissingPropertyException when trying to access a property off a
> category. (Attached is an example)
> {quote}
> index 76
> Exception in thread "Thread-77" groovy.lang.MissingPropertyException: No such
> property: millisecond for class: java.lang.Integer
> at
> org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:51)
> at
> org.codehaus.groovy.runtime.callsite.PojoMetaClassGetPropertySite.callGetProperty(PojoMetaClassGetPropertySite.java:43)
> at
> TimeCategoryTest$__spock_initializeFields_closure1$_closure4$_closure5.doCall(TimeCategoryTest.groovy:23)
> at
> TimeCategoryTest$__spock_initializeFields_closure1$_closure4$_closure5.doCall(TimeCategoryTest.groovy)
> at sun.reflect.GeneratedMethodAccessor12.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke(Method.java:497)
> at
> org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
> at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:324)
> at
> org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:292)
> at
> groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1016)
> at groovy.lang.Closure.call(Closure.java:423)
> at groovy.lang.Closure.call(Closure.java:417)
> at
> org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.use(GroovyCategorySupport.java:109)
> at
> org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.access$400(GroovyCategorySupport.java:65)
> at
> org.codehaus.groovy.runtime.GroovyCategorySupport.use(GroovyCategorySupport.java:249)
> at
> org.codehaus.groovy.runtime.DefaultGroovyMethods.use(DefaultGroovyMethods.java:403)
> {quote}
> or groovy.lang.MissingMethodException when trying to access a method from a
> category.
> {quote}
> index 82
> Exception in thread "Thread-207" groovy.lang.MissingMethodException: No
> signature of method: java.lang.String.test() is applicable for argument
> types: (java.lang.String) values: [ bar]
> Possible solutions: next(), toSet(), getAt(java.lang.String), wait(). trim(),
> toList()
> at
> org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:56)
> at
> org.codehaus.groovy.runtime.callsite.PojoMetaClassSite.call(PojoMetaClassSite.java:46)
> at
> org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:122)
> at
> CategoryTest$__spock_initializeFields_closure1$_closure5.doCall(CategoryTest.groovy:24)
> at
> CategoryTest$__spock_initializeFields_closure1$_closure5.doCall(CategoryTest.groovy)
> at sun.reflect.GeneratedMethodAccessor12.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke(Method.java:497)
> at
> org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
> at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:324)
> at
> org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:292)
> at
> groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1016)
> at groovy.lang.Closure.call(Closure.java:423)
> at groovy.lang.Closure.call(Closure.java:417)
> at
> org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.use(GroovyCategorySupport.java:109)
> at
> org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.access$400(GroovyCategorySupport.java:65)
> at
> org.codehaus.groovy.runtime.GroovyCategorySupport.use(GroovyCategorySupport.java:249)
> at
> org.codehaus.groovy.runtime.DefaultGroovyMethods.use(DefaultGroovyMethods.java:403)
> {quote}
> On the server, either one of these exceptions to appear every few days or
> weeks.
> I found a similar issue GROOVY-2105 which contains a test that reproduces
> this problem on Linux. Looking back the fix that was implemented for this
> ticket was to add synchronized to 3 methods. These changes were late removed
> in a refactor of GroovyCategorySupport.
> I have attached 3 test cases that reproduce the threading issue.
> NOTE: problem does not happen 100% of the time as it is a threading and
> timing issue, so you may have to play with the number of threads to generate
> the exception. What I have attached generates the exception on my linux box
> most of the time.
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