CaffeineCacheManager getCache method cause thread block

[huangxfchn]

• spring-context-support 5.3.18
• jdk version：17.0.4

here is my thread stack, block 193 threads

CaffeineCacheManager.java

public Cache getCache(String name) {
return this.cacheMap.computeIfAbsent(name, cacheName ->
		this.dynamic ? createCaffeineCache(cacheName) : null);
}

here is my code:

@CacheConfig(cacheNames = "branch")
public class BranchServiceImpl {
    @Cacheable(key = "#exp.id")
    public List<Branch> findById(Experiment exp) {
         // ……
    }
    
    @CachePut(key = "#exp.id")
    public List<Branch> updateCacheByExpId(Experiment exp, List<Branch> branches) {
         // ……
    }
}

[bclozel]

Could you provide a sample application that reproduces the problem? It should be a small and simple application, ideally created with https://start.spring.io. You can share it here as a zip or a git repository. Thanks!

[huangxfchn]

Could you provide a sample application that reproduces the problem? It should be a small and simple application, ideally created with https://start.spring.io. You can share it here as a zip or a git repository. Thanks!

Ok, wait a moment.

[huangxfchn]

• git repository：https://github.com/huangxfchn/spring-cache-block-demo
• run CacheTest

Then, use the jstack command to view the thread status. You can see that there are a lot of block threads. Here's one of the thread stacks

"pool-1-thread-52" #71 prio=5 os_prio=0 cpu=328.13ms elapsed=14.74s tid=0x000001994a54f540 nid=0x785c waiting for monitor entry  [0x0000007e704ff000]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(java.base@17.0.4/ConcurrentHashMap.java:1726)
        - waiting to lock <0x0000000683cfdb58> (a java.util.concurrent.ConcurrentHashMap$Node)
        at org.springframework.cache.caffeine.CaffeineCacheManager.getCache(CaffeineCacheManager.java:191)
        at com.example.demo.CacheTest.lambda$test$0(CacheTest.java:30)
        at com.example.demo.CacheTest$$Lambda$663/0x0000000800ef9238.call(Unknown Source)
        at java.util.concurrent.FutureTask.run(java.base@17.0.4/FutureTask.java:264)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(java.base@17.0.4/ThreadPoolExecutor.java:1136)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(java.base@17.0.4/ThreadPoolExecutor.java:635)
        at java.lang.Thread.run(java.base@17.0.4/Thread.java:833)

And, I found this problem in both jdk1.8 and jdk17.

I think, the CaffeineCacheManager#getCache() method can be optimized like this:

public Cache getCache(String name) {
	Cache cache = this.cacheMap.get(name);
	if (cache != null) {
		return cache;
	}
	return (Cache)this.cacheMap.computeIfAbsent(name, (cacheName) -> {
		return this.dynamic ? this.createCaffeineCache(cacheName) : null;
	});
}

[huangxfchn]

The java.util.concurrent.ConcurrentHashMap#computeIfAbsent method has lock contention, especially if concurrency is very high

[huangxfchn]

This problem leads to a lot of block threads in our online environment.