[infinispan-issues] [JBoss JIRA] (ISPN-3847) Improve resilience of ModuleLifecycle loading

[Tristan Tarrant (JIRA)]

     [ https://issues.jboss.org/browse/ISPN-3847?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tristan Tarrant reassigned ISPN-3847:
-------------------------------------

    Assignee:     (was: Mircea Markus)


> Improve resilience of ModuleLifecycle loading
> ---------------------------------------------
>
>                 Key: ISPN-3847
>                 URL: https://issues.jboss.org/browse/ISPN-3847
>             Project: Infinispan
>          Issue Type: Enhancement
>          Components: Core
>    Affects Versions: 6.0.1.Final
>            Reporter: Paul Ferraro
>
> 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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