Vihang Karajgaonkar created HADOOP-14195:
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Summary: CredentialProviderFactory is not thread-safe
Key: HADOOP-14195
URL: https://issues.apache.org/jira/browse/HADOOP-14195
Project: Hadoop Common
Issue Type: Bug
Reporter: Vihang Karajgaonkar
Multi-threaded access to CredentialProviderFactory is not thread-safe because
{{java.util.ServiceLoader}} is not thread-safe (as noted in its Java doc).
Thanks to [~jzhuge] I was able to reproduce this issue but creating a simple
multi-threaded application which executes the following code in parallel.
{code:java}
for (int i = 0; i < ITEMS; i++) {
futures.add(executor.submit(new Callable<Void>() {
@Override
public Void call() throws Exception {
boolean found = false;
for (CredentialProviderFactory factory : serviceLoader) {
CredentialProvider kp = factory.createProvider(uri,
conf);
if (kp != null) {
result.add(kp);
found = true;
break;
}
}
if (!found) {
throw new IOException(Thread.currentThread() + "No
CredentialProviderFactory for " + uri);
} else {
System.out.println(Thread.currentThread().getName() + "
found credentialProvider for " + path);
}
return null;
}
}));
}
{code}
I see the following exception trace when I execute the above code.
{code:java}
java.util.concurrent.ExecutionException: java.util.NoSuchElementException
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:192)
at TestCredentialProvider.main(TestCredentialProvider.java:58)
Caused by: java.util.NoSuchElementException
at java.net.URLClassLoader$3.nextElement(URLClassLoader.java:615)
at java.net.URLClassLoader$3.nextElement(URLClassLoader.java:590)
at sun.misc.CompoundEnumeration.nextElement(CompoundEnumeration.java:61)
at
java.util.ServiceLoader$LazyIterator.hasNextService(ServiceLoader.java:357)
at java.util.ServiceLoader$LazyIterator.hasNext(ServiceLoader.java:393)
at java.util.ServiceLoader$1.hasNext(ServiceLoader.java:474)
at TestCredentialProvider$1.call(TestCredentialProvider.java:38)
at TestCredentialProvider$1.call(TestCredentialProvider.java:1)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
{code}
I also see a NPE sometimes
{code:java}
java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:192)
at TestCredentialProvider.main(TestCredentialProvider.java:58)
Caused by: java.lang.NullPointerException
at java.util.ServiceLoader.parse(ServiceLoader.java:304)
at java.util.ServiceLoader.access$200(ServiceLoader.java:185)
at
java.util.ServiceLoader$LazyIterator.hasNextService(ServiceLoader.java:357)
at java.util.ServiceLoader$LazyIterator.hasNext(ServiceLoader.java:393)
at java.util.ServiceLoader$1.hasNext(ServiceLoader.java:474)
at TestCredentialProvider$1.call(TestCredentialProvider.java:38)
at TestCredentialProvider$1.call(TestCredentialProvider.java:1)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
{code}
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