A deadlock occurs in my application while one thread performs a query on a mongo db, causing an application event to be fired, while another thread attempts to create a bean with an AutowireCapableBeanFactory
.
This happens in the constructor of a @Service and prevents the startup of the entire application as the service is created on startup.
Pseudocode:
@Service
public class MyService {
@Autowired
public MyService(AutowireCapableBeanFactory factory, TaskScheduler scheduler) {
MyFirstCommand command1 = factory.getBean(MyFirstCommand.class);
scheduler.schedule(command1, new Date());
MySecondCommand command2 = factory.getBean(MySecondCommand.class);
scheduler.schedule(command2, new Date());
}
}
public class MyFirstCommand extends Runnable {
@Autowired MongoOperations mongo;
@Override
public void run() {
mongo.findById("some-id", MyData.class);
}
}
Note that i have some AbstractMongoEventListener
s registered as @Component
s.
The deadlock occurs while one thread in MyFirstCommand.run()
performs mongo.findById()
. The other thread is in the constructor of MyService
performing factory.getBean(MySecondCommand.class):
Found one Java-level deadlock:
=============================
"pool-1-thread-1":
waiting to lock monitor 0x00007fd05d5bf5d8 (object 0x00000000816d0970, a java.util.concurrent.ConcurrentHashMap),
which is held by "main"
"main":
waiting for ownable synchronizer 0x0000000081ed8468, (a java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync),
which is held by "pool-1-thread-1"
Java stack information for the threads listed above:
===================================================
"pool-1-thread-1":
at org.springframework.context.event.AbstractApplicationEventMulticaster.getApplicationListeners(AbstractApplicationEventMulticaster.java:179)
- waiting to lock <0x00000000816d0970> (a java.util.concurrent.ConcurrentHashMap)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:381)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:335)
at org.springframework.data.mapping.context.AbstractMappingContext.addPersistentEntity(AbstractMappingContext.java:326)
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:179)
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:139)
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:66)
at org.springframework.data.mongodb.core.MongoTemplate.determineCollectionName(MongoTemplate.java:1976)
at org.springframework.data.mongodb.core.MongoTemplate.findById(MongoTemplate.java:607)
"main":
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x0000000081ed8468> (a java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireShared(AbstractQueuedSynchronizer.java:967)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireShared(AbstractQueuedSynchronizer.java:1283)
at java.util.concurrent.locks.ReentrantReadWriteLock$ReadLock.lock(ReentrantReadWriteLock.java:727)
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:160)
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:139)
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:66)
at org.springframework.data.mongodb.repository.support.MongoRepositoryFactory.getEntityInformation(MongoRepositoryFactory.java:118)
at org.springframework.data.mongodb.repository.support.MongoRepositoryFactory.getTargetRepository(MongoRepositoryFactory.java:92)
at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:185)
at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.initAndReturn(RepositoryFactoryBeanSupport.java:251)
at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet(RepositoryFactoryBeanSupport.java:237)
at org.springframework.data.mongodb.repository.support.MongoRepositoryFactoryBean.afterPropertiesSet(MongoRepositoryFactoryBean.java:108)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1637)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1574)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:545)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
How come Spring isn't thread safe here? What can i do to avoid this deadlock?
This deadlock occurs due to a bug in Spring. I have created an issue in their JIRA: DATACMNS-901.
As a workaround i am now creating all runnable beans before scheduling them:
@Autowired
public MyService(AutowireCapableBeanFactory factory, TaskScheduler scheduler) {
MyFirstCommand command1 = factory.getBean(MyFirstCommand.class);
MySecondCommand command2 = factory.getBean(MySecondCommand.class);
scheduler.schedule(command2, new Date());
scheduler.schedule(command1, new Date());
}
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