Shared session usage in AEM 6.3 (oh no, not again!)
For our client we are developing a specific health check which analyses a page output traversing the tree of child pages.
I am aware that a shared session usage is a well known anti-pattern (https://cqdump.wordpress.com/2015/03/02/aem-scaling-patterns-avoid-shared-sessions/ and https://github.com/joerghoh/cqdump/blob/master/examples/bundle/src/main/java/de/joerghoh/cq5/examples/oak/services/impl/GoodConfigurationServiceImpl.java) in AEM and keeping this in mind I created this code:
Assuming that I have a list of nodes to check:
for (Node node : nodes) {
Future f = completionService.submit(testResultFunction(node.getPath()));
futures.add(f);
}
...
private Callable<String> testResultFunction(final String nodePath) {
return () -> Templates.serviceResourceResolverFunction(Constants.ServiceUsers.READ_SERVICE,
resourceResolverFactory, resourceResolver -> {
String result = requestService.doGet(checkedPageUrl, resourceResolver).getContent();
...
return result;
});
}
Templates.serviceResourceResolverFunction() looks like this:
public static <R> R serviceResourceResolverFunction(String serviceName, @Nonnull ResourceResolverFactory resourceResolverFactory,
@Nonnull Function<ResourceResolver, R> function) {
Map<String, Object> map = Collections.singletonMap(ResourceResolverFactory.SUBSERVICE, serviceName);
ResourceResolver resolver = null;
try {
resolver = resourceResolverFactory.getServiceResourceResolver(map);
return function.apply(resolver);
} catch (LoginException e) {
LOG.error("Access denied", e);
return null;
} finally {
if (resolver != null && resolver.isLive()) {
resolver.close();
}
}
}
I am receiving an output which forces me to scratch my head over and over again:
01.03.2018 15:51:00.880 *WARN* [ForkJoinPool-2-worker-1] org.apache.jackrabbit.oak.jcr.delegate.SessionDelegate Attempted to perform hasProperty while thread ForkJoinPool-2-worker-2 was concurrently writing to this session. Blocked until the other thread finished using this session. Please review your code to avoid concurrent use of a session. ...and so on...
In debugger i see that I receive a new resourceResolver per every request made, and I am not writing anything to the session (?!), so I can only wonder what's the problem here.
Any help will be much appreciated!
Edited 09.03.2018 by Evgeny Tugarev
