paul-rogers commented on code in PR #12816:
URL: https://github.com/apache/druid/pull/12816#discussion_r935024082
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indexing-service/src/main/java/org/apache/druid/indexing/common/task/HadoopTask.java:
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@@ -48,13 +49,11 @@
public abstract class HadoopTask extends AbstractBatchIndexTask
{
private static final Logger log = new Logger(HadoopTask.class);
- private static final ExtensionsConfig EXTENSIONS_CONFIG;
-
- static final Injector INJECTOR = GuiceInjectors.makeStartupInjector();
- static {
- EXTENSIONS_CONFIG = INJECTOR.getInstance(ExtensionsConfig.class);
- }
+ // Note: static variables mean that this task cannot run in a shared JVM,
Review Comment:
The issue here is more basic: static variables. If task A and task B both
run in the Indexer, then they share a single copy of the static variable
(unless the Indexer loads them in isolated class loaders.) By contrast, the
`ExtensionsLoader` was converted from static variables to a Guice-injected
singleton to avoid this issue. For `ExtensionsLoader` the only time two
instances will appear in the same JVM is in tests, which used to have special
code to undo the static variables between tests.
The `HadoopTask` approach seems more like a bug than a feature. A good
enhancement would be to modify the `HadoopTask` to use Guice (and the
`ExtensionsLoader`, perhaps modified for the Hadoop dependencies) to avoid the
static variable issue.
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