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https://issues.apache.org/jira/browse/HADOOP-10829?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15611587#comment-15611587
]
Larry McCay commented on HADOOP-10829:
--------------------------------------
[~rakeshr] - I am inclined to prefer the approach used in KeyProviderFactory
instead which avoids the lazy loading by iterating over the providers in a
static initialization block. This avoids the need for synchronization during
each call to getProviders for every client in a JVM.
{code}
public abstract KeyProvider createProvider(URI providerName,
Configuration conf
) throws IOException;
private static final ServiceLoader<KeyProviderFactory> serviceLoader =
ServiceLoader.load(KeyProviderFactory.class,
KeyProviderFactory.class.getClassLoader());
// Iterate through the serviceLoader to avoid lazy loading.
// Lazy loading would require synchronization in concurrent use cases.
static {
Iterator<KeyProviderFactory> iterServices = serviceLoader.iterator();
while (iterServices.hasNext()) {
iterServices.next();
}
}
public static List<KeyProvider> getProviders(Configuration conf
) throws IOException {
List<KeyProvider> result = new ArrayList<KeyProvider>();
for(String path: conf.getStringCollection(KEY_PROVIDER_PATH)) {
try {
URI uri = new URI(path);
KeyProvider kp = get(uri, conf);
if (kp != null) {
result.add(kp);
} else {
throw new IOException("No KeyProviderFactory for " + uri + " in " +
KEY_PROVIDER_PATH);
}
} catch (URISyntaxException error) {
throw new IOException("Bad configuration of " + KEY_PROVIDER_PATH +
" at " + path, error);
}
}
return result;
}
{code}
What do you think?
> Iteration on CredentialProviderFactory.serviceLoader is thread-unsafe
> ----------------------------------------------------------------------
>
> Key: HADOOP-10829
> URL: https://issues.apache.org/jira/browse/HADOOP-10829
> Project: Hadoop Common
> Issue Type: Bug
> Components: security
> Affects Versions: 2.6.0
> Reporter: Benoy Antony
> Assignee: Benoy Antony
> Labels: BB2015-05-TBR
> Attachments: HADOOP-10829.003.patch, HADOOP-10829.patch,
> HADOOP-10829.patch
>
>
> CredentialProviderFactory uses _ServiceLoader_ framework to load
> _CredentialProviderFactory_
> {code}
> private static final ServiceLoader<CredentialProviderFactory> serviceLoader
> =
> ServiceLoader.load(CredentialProviderFactory.class);
> {code}
> The _ServiceLoader_ framework does lazy initialization of services which
> makes it thread unsafe. If accessed from multiple threads, it is better to
> synchronize the access.
> Similar synchronization has been done while loading compression codec
> providers via HADOOP-8406.
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