removalListener not getting invoked

[manishkrishan]

I am trying to get a removalListener as below but it is never being invoked. Below is sample code what I tried. Any suggestion ?

. . . 
import com.github.benmanes.caffeine.cache.Cache;
import com.github.benmanes.caffeine.cache.Caffeine;
import com.github.benmanes.caffeine.cache.RemovalCause;
import com.github.benmanes.caffeine.cache.RemovalListener;
. . . 

class Foo {
   private static Map<String, Timestamp> s_cacheMap;

   private static class TestListener implements RemovalListener<String, Timestamp> {
      @Override
      public void onRemoval(String sKey, Timestamp arg1, RemovalCause cause) {
         System.out.printf("Key %s was removed (%s)%n", sKey, cause);
      }
   }
   private static final TestListener sListener = new TestListener();
   static {
      Cache<String, Timestamp> cache = Caffeine.newBuilder()
                                               .initialCapacity(1)   
                                               .maximumSize(1) //kept low just to invoke Removal Listener
                                               .removalListener(sListener)
                                               .build();

      s_cacheMap = cache.asMap();
   }

   @Test
   public void testRemoval() {
      s_cacheMap.put("a", new Timestamp(1));
      s_cacheMap.put("b", new Timestamp(2));
      s_cacheMap.put("a1", new Timestamp(3));
      s_cacheMap.put("b2", new Timestamp(4));
   }
}

Using caffeine 2.9.2 with JAVA 8

[ben-manes]

By default the cache defers to an executor for non-critical path logic, like notifying the removal listener, since we don't know how expensive that work is and do not want to impact the caller if it would increase user-facing latencies. Most likely your test is completing before the ForkJoinPool.commonPool() executes the work. You can use Caffeine.executor(Runnable::run) to disable this behavior (as the cache's own logic is fast) or wait for the work to finish (e.g. using Awaitility).