feat(java): remove soft/weak ref values from thread safe fury

[chaokunyang]

What does this PR do?

remove soft/weak ref values from thread safe fury

Related issues

Closes #1632

Does this PR introduce any user-facing change?

• Does this PR introduce any public API change?
• Does this PR introduce any binary protocol compatibility change?

Benchmark

[chaokunyang]

Hi @MrChang0 , could you help review this PR. I plan to make a new release for fury when this got merged. We have some minor bugs in fury 0.5.0 release

[MrChang0]

great, I thinking about that we can add classLoaderFuryPooledCache.cleanup() in getFury(), make cache clean more timely.

[chaokunyang]

cleanup

@MrChang0 Could you elaborate more details? If we cleanup classloader in getFury, Fury will be created every time when getFury is called

[MrChang0]

we call cleanup() to clean data which is expired or drain key/value reference. because cache will hold on data much more time even data is needed to be clean. so if the cache does't operate frequently enough, we can use cleanup(). maybe it can solve class leak question.

[chaokunyang]

we call cleanup() to clean data which is expired or drain key/value reference. because cache will hold on data much more time even data is needed to be clean. so if the cache does't operate frequently enough, we can use cleanup(). maybe it can solve class leak question.

I still don't get it. We cleanup the classloader and associated map in:

  public void clearClassLoader(ClassLoader loader) {
    classLoaderFuryPooledCache.invalidate(loader);
    classLoaderLocal.remove();
  }

Could you share some code?

[MrChang0]

just like

  @Test
    public void testCache() throws InterruptedException {
      Cache<String, String> cache = CacheBuilder.newBuilder().expireAfterAccess(Duration.ofSeconds(1)).build();
      cache.put("1", "1");
      cache.put("2", "2");
      Assert.assertEquals(cache.size(), 2);
      Thread.sleep(800);
      cache.getIfPresent("1");
      cache.cleanUp();
      Assert.assertEquals(cache.size(), 2);
      Thread.sleep(800);
      cache.getIfPresent("1");
      Assert.assertEquals(cache.size(), 2);
      Thread.sleep(800);
      cache.getIfPresent("1");
      Assert.assertEquals(cache.size(), 2);
      cache.cleanUp();
      Assert.assertEquals(cache.size(), 1);
  }

[chaokunyang]

just like

  @Test
    public void testCache() throws InterruptedException {
      Cache<String, String> cache = CacheBuilder.newBuilder().expireAfterAccess(Duration.ofSeconds(1)).build();
      cache.put("1", "1");
      cache.put("2", "2");
      Assert.assertEquals(cache.size(), 2);
      Thread.sleep(800);
      cache.getIfPresent("1");
      cache.cleanUp();
      Assert.assertEquals(cache.size(), 2);
      Thread.sleep(800);
      cache.getIfPresent("1");
      Assert.assertEquals(cache.size(), 2);
      Thread.sleep(800);
      cache.getIfPresent("1");
      Assert.assertEquals(cache.size(), 2);
      cache.cleanUp();
      Assert.assertEquals(cache.size(), 1);
  }

Clean it up every time will create Fury everytime, which is very expensive. Fury needs be cached.

[MrChang0]

I explain it.

  @Test
    public void testCache() throws InterruptedException {
      Cache<String, String> cache = CacheBuilder.newBuilder().expireAfterAccess(Duration.ofSeconds(1)).build();
      cache.put("1", "1");
      cache.put("2", "2");
      Assert.assertEquals(cache.size(), 2);
      Thread.sleep(800);
      cache.getIfPresent("1");
      // clean up do nothing, because key1, key2 both alive.
      cache.cleanUp();
      Assert.assertEquals(cache.size(), 2);
      Thread.sleep(800);
      cache.getIfPresent("1");
      Assert.assertEquals(cache.size(), 2);
      Thread.sleep(800);
      cache.getIfPresent("1");
     // key2 is expired, but won't be cleared from cache. may be case memory leak. now cache size is 2.
      Assert.assertEquals(cache.size(), 2);
      cache.cleanUp();
     // clean up clear key2, because key2 is expired. so size of cache becomes 1.
      Assert.assertEquals(cache.size(), 1);
  }

I mean that when cache have expireAfterAccess option. it may save data which should expired too much time.
so we cleanup timely won't create Fury everytime, it just clear data which is expired.

[chaokunyang]

I see, thanks. Clean up it every time is not cheap for small objects.

Fury will replace guava cache with a fury implemented one, see more on #1113 . We can support clean up cache timely when access expired

[MrChang0]

fine, if we want remove guava dependency, we can try caffeine, maybe can shaded in fury.

[chaokunyang]

Yep, this is a smaller dependency. Fury is a low-level library, we want to make a zero-dependency in the long time. The cache usage in Fury is very simple. Maybe we can implement it manually too.