Paul Ferraro created ISPN-3847:
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Summary: Improve resilience of ModuleLifecycle loading
Key: ISPN-3847
URL:
https://issues.jboss.org/browse/ISPN-3847
Project: Infinispan
Issue Type: Enhancement
Components: Core API
Affects Versions: 6.0.0.Final
Reporter: Paul Ferraro
Assignee: Mircea Markus
Currently, org.infinispan.util.ModuleProperties.resolveModuleLifecycles(...) uses a
ServiceLoader to directly load ModuleLifecycle instances. However, if a jar exists on the
classpath containing a META-INF/services/org.infinispan.lifecycle.ModuleLifecycle file,
but the class name contained within cannot be loaded, due to, for example, a dependency
jar being missing, then the whole resolveModuleLifecycles(...) method chokes due to a
ServiceConfigurationError. For example, if infinispan-query is on the classpath, but
hibernate-search is not, Infinispan is unusable.
I can see 2 ways to fix this:
1. Use the iterator directly instead of the enhanced for-loop, and catch and handle the
SCE:
e.g.
{code:java}
Iterator<ModuleLifecycle> lifecycles = ServiceLoader.load(ModuleLifecycle.class,
classLoader);
while (lifecycles.hasNext()) {
try {
ModuleLifecycle lifecycle = lifecycles.next(); // This can throw SCE
result.add(lifecycle);
} catch (ServiceConfigurationError e) {
// Log error
}
}
{code}
2. Introduce a ModuleLifecycleProvider abstraction - that won't throw an SCE. The
ServiceLoader spec actually recommends this:
"The provider class is typically not the entire provider itself but rather a proxy
which contains enough information to decide whether the provider is able to satisfy a
particular request together with code that can create the actual provider on
demand."
In the end, this would look something like:
{code:java}
for (ModuleLifecycleFactory factory: ServiceLoader.load(ModuleLifecycleFactory.class,
classLoader)) {
if (factory.isEnabled()) { // returns true if create method will not throw SCE
ModuleLifecycle lifecycle = factory.createModuleLifecycle();
result.add(lifecycle);
}
}
{code}
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