resharding- support force feature coverage for testing

Author: Sunjeet

hollow/src/main/java/com/netflix/hollow/api/producer/AbstractHollowProducer.java

@@ -95,9 +95,9 @@ abstract class AbstractHollowProducer {
     boolean isInitialized;
 
     private final long targetMaxTypeShardSize;
-    private final boolean allowTypeResharding;
     private final boolean focusHoleFillInFewestShards;
-
+    private final boolean allowTypeResharding;
+    private final boolean forceCoverageOfTypeResharding;   // exercise re-sharding often (for testing)
 
     @Deprecated
     public AbstractHollowProducer(
@@ -106,7 +106,7 @@ public AbstractHollowProducer(
         this(new HollowFilesystemBlobStager(), publisher, announcer,
                 Collections.emptyList(),
                 new VersionMinterWithCounter(), null, 0,
-                DEFAULT_TARGET_MAX_TYPE_SHARD_SIZE, false, false, null,
+                DEFAULT_TARGET_MAX_TYPE_SHARD_SIZE, false, false, false, null,
                 new DummyBlobStorageCleaner(), new BasicSingleProducerEnforcer(),
                 null, true);
     }
@@ -118,7 +118,8 @@ public AbstractHollowProducer(
         this(b.stager, b.publisher, b.announcer,
                 b.eventListeners,
                 b.versionMinter, b.snapshotPublishExecutor,
-                b.numStatesBetweenSnapshots, b.targetMaxTypeShardSize, b.focusHoleFillInFewestShards, b.allowTypeResharding,
+                b.numStatesBetweenSnapshots, b.targetMaxTypeShardSize, b.focusHoleFillInFewestShards,
+                b.allowTypeResharding, b.forceCoverageOfTypeResharding,
                 b.metricsCollector, b.blobStorageCleaner, b.singleProducerEnforcer,
                 b.hashCodeFinder, b.doIntegrityCheck);
     }
@@ -134,6 +135,7 @@ private AbstractHollowProducer(
             long targetMaxTypeShardSize,
             boolean focusHoleFillInFewestShards,
             boolean allowTypeResharding,
+            boolean forceCoverageOfTypeResharding,
             HollowMetricsCollector<HollowProducerMetrics> metricsCollector,
             HollowProducer.BlobStorageCleaner blobStorageCleaner,
             SingleProducerEnforcer singleProducerEnforcer,
@@ -150,6 +152,7 @@ private AbstractHollowProducer(
         this.doIntegrityCheck = doIntegrityCheck;
         this.targetMaxTypeShardSize = targetMaxTypeShardSize;
         this.allowTypeResharding = allowTypeResharding;
+        this.forceCoverageOfTypeResharding = forceCoverageOfTypeResharding;
         this.focusHoleFillInFewestShards = focusHoleFillInFewestShards;
 
         HollowWriteStateEngine writeEngine = hashCodeFinder == null
@@ -399,6 +402,12 @@ long runCycle(
                         !writeEngine.hasIdenticalSchemas(readStates.current().getStateEngine());
                 updateHeaderTags(writeEngine, toVersion, schemaChangedFromPriorVersion);
 
+                if (allowTypeResharding && forceCoverageOfTypeResharding) {
+                    int randomFactor = (int) Math.pow(2, (int) (Math.random() * 9) - 4); // random power of 2 in the range [-4, 4]
+                    long adjustedShardSize = targetMaxTypeShardSize * randomFactor;
+                    writeEngine.setTargetMaxTypeShardSize(adjustedShardSize);
+                }
+
                 // 3a. Publish, run checks & validation, then announce new state consumers
                 publish(listeners, toVersion, artifacts);
 

hollow/src/main/java/com/netflix/hollow/api/producer/HollowProducer.java

@@ -43,7 +43,6 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
-import java.util.Vector;
 import java.util.concurrent.Executor;
 
 /**
@@ -732,6 +731,7 @@ public static class Builder<B extends HollowProducer.Builder<B>> {
         int numStatesBetweenSnapshots = 0;
         boolean focusHoleFillInFewestShards = false;
         boolean allowTypeResharding = false;
+        boolean forceCoverageOfTypeResharding = false;
         long targetMaxTypeShardSize = DEFAULT_TARGET_MAX_TYPE_SHARD_SIZE;
         HollowMetricsCollector<HollowProducerMetrics> metricsCollector;
         BlobStorageCleaner blobStorageCleaner = new DummyBlobStorageCleaner();
@@ -883,7 +883,20 @@ public B withFocusHoleFillInFewestShards(boolean focusHoleFillInFewestShards) {
          * Also requires consumers of the delta chain to be on a recent Hollow library version that supports re-sharding at the time of delta application.
          */
         public B withTypeResharding(boolean allowTypeResharding) {
+            return (B) withTypeResharding(allowTypeResharding, false);
+        }
+
+        /**
+         * Experimental: Setting this will allow producer to adjust number of shards per type in the course of a delta chain.
+         *
+         * @param allowTypeResharding enable type resharding feature, see {@link #withTypeResharding(boolean)} for more details.
+         * @param forceCoverage a boolean indicating whether to attempt to induce resharding on every cycle. This a feature
+         *                                    for exercising resharding coverage frequently in test environments, and is not expected
+         *                                    to be set for production environments.
+         */
+        public B withTypeResharding(boolean allowTypeResharding, boolean forceCoverage) {
             this.allowTypeResharding = allowTypeResharding;
+            this.forceCoverageOfTypeResharding = forceCoverage;
             return (B) this;
         }