Set min translated per partition size to 1 instead of 2

hazelcast/src/main/java/com/hazelcast/map/impl/eviction/EvictionChecker.java

@@ -53,7 +53,7 @@
 public class EvictionChecker {
 
     protected static final double ONE_HUNDRED_PERCENT = 100D;
-    private static final int MIN_SANE_PER_PARTITION_SIZE = 2;
+    private static final int MIN_TRANSLATED_PARTITION_SIZE = 1;
 
     protected final ILogger logger;
     protected final MapServiceContext mapServiceContext;
@@ -107,15 +107,15 @@ public boolean checkEvictable(RecordStore recordStore) {
     }
 
     protected boolean checkPerNodeEviction(RecordStore recordStore) {
-        double recordStoreSize = translatePerNodeSizeToRecordStoreSize(recordStore);
-        return recordStore.size() > recordStoreSize;
+        double maxAllowedStoreSize = translatePerNodeSizeToPartitionSize(recordStore);
+        return recordStore.size() > maxAllowedStoreSize;
     }
 
     /**
      * Calculates and returns the expected maximum size of an evicted record-store
      * when {@link com.hazelcast.config.MaxSizeConfig.MaxSizePolicy#PER_NODE PER_NODE} max-size-policy is used.
      */
-    public double translatePerNodeSizeToRecordStoreSize(RecordStore recordStore) {
+    public double translatePerNodeSizeToPartitionSize(RecordStore recordStore) {
         MapConfig mapConfig = recordStore.getMapContainer().getMapConfig();
         MaxSizeConfig maxSizeConfig = mapConfig.getMaxSizeConfig();
         NodeEngine nodeEngine = mapServiceContext.getNodeEngine();
@@ -124,19 +124,19 @@ public double translatePerNodeSizeToRecordStoreSize(RecordStore recordStore) {
         int memberCount = nodeEngine.getClusterService().getSize(DATA_MEMBER_SELECTOR);
         int partitionCount = nodeEngine.getPartitionService().getPartitionCount();
 
-        double perNodeMaxRecordStoreSize = (1D * configuredMaxSize * memberCount / partitionCount);
-        if (perNodeMaxRecordStoreSize < 1) {
-            perNodeMaxRecordStoreSize = MIN_SANE_PER_PARTITION_SIZE;
+        double translatedPartitionSize = (1D * configuredMaxSize * memberCount / partitionCount);
+        if (translatedPartitionSize < 1) {
+            translatedPartitionSize = MIN_TRANSLATED_PARTITION_SIZE;
             if (misconfiguredPerNodeMaxSizeWarningLogged.compareAndSet(false, true)) {
                 int minMaxSize = (int) Math.ceil((1D * partitionCount / memberCount));
-                int newSize = MIN_SANE_PER_PARTITION_SIZE * partitionCount / memberCount;
+                int newSize = MIN_TRANSLATED_PARTITION_SIZE * partitionCount / memberCount;
                 logger.warning(format("The max size configuration for map \"%s\" does not allow any data in the map. "
                                 + "Given the current cluster size of %d members with %d partitions, max size should be at "
                                 + "least %d. Map size is forced set to %d for backward compatibility", mapConfig.getName(),
                         memberCount, partitionCount, minMaxSize, newSize));
             }
         }
-        return perNodeMaxRecordStoreSize;
+        return translatedPartitionSize;
     }
 
     protected boolean checkPerPartitionEviction(String mapName, MaxSizeConfig maxSizeConfig, int partitionId) {

hazelcast/src/test/java/com/hazelcast/map/EvictionMaxSizePolicyTest.java

@@ -65,7 +65,6 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
-
 @RunWith(HazelcastParallelClassRunner.class)
 @Category({QuickTest.class, ParallelTest.class})
 public class EvictionMaxSizePolicyTest extends HazelcastTestSupport {
@@ -90,7 +89,7 @@ public void testPerNodePolicy_afterGracefulShutdown() {
         int perNodeMaxSize = 1000;
 
         // eviction takes place if a partitions size exceeds this number
-        // see EvictionChecker#translatePerNodeSizeToRecordStoreSize
+        // see EvictionChecker#translatePerNodeSizeToPartitionSize
         double maxPartitionSize = 1D * nodeCount * perNodeMaxSize / PARTITION_COUNT;
 
         String mapName = "testPerNodePolicy_afterGracefulShutdown";
@@ -113,15 +112,36 @@ public void testPerNodePolicy_afterGracefulShutdown() {
                 int mapSize = node.getMap(mapName).size();
                 String message = format("map size is %d and it should be smaller "
                                 + "than maxPartitionSize * PARTITION_COUNT which is %.0f",
-                        mapSize,  maxPartitionSize * PARTITION_COUNT);
-
-                System.err.println(message);
+                        mapSize, maxPartitionSize * PARTITION_COUNT);
 
                 assertTrue(message, mapSize <= maxPartitionSize * PARTITION_COUNT);
             }
         }
     }
 
+    /**
+     * Eviction starts if a partitions' size exceeds this number:
+     *
+     * double maxPartitionSize = 1D * nodeCount * perNodeMaxSize / PARTITION_COUNT;
+     *
+     * when calculated `maxPartitionSize` is under 1, we should forcibly set it
+     * to 1, otherwise all puts will immediately be removed by eviction.
+     */
+    @Test
+    public void testPerNodePolicy_does_not_cause_unexpected_eviction_when_translated_partition_size_under_one() {
+        String mapName = randomMapName();
+        int maxSize = PARTITION_COUNT / 2;
+        Config config = createConfig(PER_NODE, maxSize, mapName);
+        HazelcastInstance node = createHazelcastInstance(config);
+        IMap map = node.getMap(mapName);
+
+        for (int i = 0; i < PARTITION_COUNT; i++) {
+            String keyForPartition = generateKeyForPartition(node, i);
+            map.put(keyForPartition, i);
+            assertEquals(i, map.get(keyForPartition));
+        }
+    }
+
     @Test
     public void testOwnerAndBackupEntryCountsAreEqualAfterEviction_whenPerNodeMaxSizePolicyIsUsed() throws Exception {
         String mapName = randomMapName();