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https://issues.apache.org/jira/browse/GROOVY-7407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15924058#comment-15924058
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Jex Jexler commented on GROOVY-7407:
------------------------------------
I tried to see if locking "per artifact" (group:module:version) could be a
solution, using the following code in GrapeIvy to lock on grab() and resolve():
{code:java}
private Map<String,Object> lockMap = new HashMap<>()
private Object getLock(Map... dependencies) {
String group
String module
String version
for (Map dep : dependencies) {
if (dep.group != null) {
group = dep.group
}
if (dep.module != null) {
module = dep.module
}
if (dep.version != null) {
version = dep.version
}
}
String key = "$group:$module:$version"
synchronized (lockMap) {
Object obj = lockMap.get(key)
if (obj == null) {
obj = new Object()
lockMap.put(key, obj)
}
return obj
}
}
{code}
{code:java}
public grab(Map args, Map... dependencies) {
synchronized (getLock(dependencies)) {
{code}
but this did not help with a modified version of GroovyCompileConcurrencyTest
in which one in 10 compilation units used guava versions 10,11,12, ...19.
So whatever the issue is, locking on the GrapeEngine interface level per
artifact would apparently not to be a viable approach.
> Compilation not thread safe if Grape / Ivy is used in Groovy scripts
> --------------------------------------------------------------------
>
> Key: GROOVY-7407
> URL: https://issues.apache.org/jira/browse/GROOVY-7407
> Project: Groovy
> Issue Type: Bug
> Components: Compiler, Grape
> Affects Versions: 2.4.3
> Environment: Essentially independent of the environment, as long as
> Groovy scripts use Grape; also this bug seems to be present since at least
> Groovy 1.7.5.
> Reporter: Jex Jexler
> Priority: Minor
> Labels: Compile, Grape, Groovy, Ivy
> Attachments: GrapeAndGroovyShellConcurrencyTest.java,
> GroovyCompileConcurrencyTest.java,
> stacktrace-GrapeAndGroovyShellConcurrencyTest-1.txt,
> stacktrace-GrapeAndGroovyShellConcurrencyTest-2.txt,
> stacktrace-GroovyCompileConcurrencyTest-1.txt,
> stacktrace-GroovyCompileConcurrencyTest-2.txt,
> WorkaroundGroovy7407WrappingGrapeEngine.java
>
>
> If Groovy scripts that import the same libraries via Grape are compiled in
> separate threads, compilation may fail due to race conditions.
> This does not happen if several threads use the *same* instance of
> GroovyClassLoader (GCL), because parseClass() uses synchronization.
> But as soon as different GCLs are used in separate threads or if the compiler
> is used directly (CompilationUnit.compile()), the issue occurs and
> compilation can fail.
> Two Java unit tests have be attached, which reproduce the issue, although
> this cannot be guaranteed with 100% certainty, because there is a race
> condition.
> Two different stacktraces have been observed for each unit test (with origins
> in Grape and in Ivy), which have also been attached (plus in a different
> environment (Tomcat webapp CentOS) once a an exception down in Ivy had been
> observed that seemed to be related to unzipping a JAR file, but no precise
> record of that exists any more).
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