Update license header, short circuiting and streaming

Author: Alexander Patrikalakis

src/main/java/com/amazon/janusgraph/diskstorage/dynamodb/AbstractDynamoDbStore.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2014-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License").
  * You may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@
 import java.util.List;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
 
 import com.amazonaws.services.dynamodbv2.model.CreateTableRequest;
 import com.amazonaws.services.dynamodbv2.model.DeleteItemRequest;
@@ -186,21 +187,18 @@ String encodeKeyForLog(final StaticBuffer key) {
     }
 
     String encodeForLog(final List<?> columns) {
-        final StringBuilder result = new StringBuilder("[");
-        for (int i = 0; i < columns.size(); i++) {
-            final Object obj = columns.get(i);
-            StaticBuffer column = null;
-            if (obj instanceof StaticBuffer) {
-                column = (StaticBuffer) obj;
-            } else if (obj instanceof Entry) {
-                column = ((Entry) obj).getColumn();
-            }
-            result.append(encodeKeyForLog(column));
-            if (i < columns.size() - 1) {
-                result.append(",");
-            }
-        }
-        return result.append("]").toString();
+        return columns.stream()
+                .map(obj -> {
+                    if (obj instanceof StaticBuffer) {
+                        return (StaticBuffer) obj;
+                    } else if (obj instanceof Entry) {
+                        return ((Entry) obj).getColumn();
+                    } else {
+                        return null;
+                    }
+                })
+                .map(this::encodeKeyForLog)
+                .collect(Collectors.joining(",", "[", "]"));
     }
 
     @Override

src/main/java/com/amazon/janusgraph/diskstorage/dynamodb/BackendRuntimeException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2014-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License").
  * You may not use this file except in compliance with the License.
@@ -35,9 +35,8 @@ public BackendException getBackendException() {
         final Throwable throwable = super.getCause();
         if (throwable instanceof BackendException) {
             return (BackendException) throwable;
-        } else {
-            return null;
         }
+        return null;
     }
 
     private static final long serialVersionUID = 6184087040805925812L;

src/main/java/com/amazon/janusgraph/diskstorage/dynamodb/Client.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2014-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  * Portions copyright Titan: Distributed Graph Database - Copyright 2012 and onwards Aurelius.
  *
  * Licensed under the Apache License, Version 2.0 (the "License").
@@ -127,9 +127,10 @@ public Client(final Configuration config) {
             Constants.DYNAMODB_INITIAL_RETRY_MILLIS.getName() + " must be at least 1");
 
         final double controlPlaneRate = config.get(Constants.DYNAMODB_CONTROL_PLANE_RATE);
-        Preconditions.checkArgument(controlPlaneRate >= 0,
+        Preconditions.checkArgument(controlPlaneRate > 0,
             "must have a positive control plane rate");
-        final RateLimiter controlPlaneRateLimiter = RateLimiter.create(controlPlaneRate);
+        final RateLimiter controlPlaneRateLimiter = RateLimiterCreator.createBurstingLimiter(controlPlaneRate,
+                DEFAULT_BURST_BUCKET_SIZE_IN_SECONDS);
 
         final Map<String, RateLimiter> readRateLimit = new HashMap<>();
         final Map<String, RateLimiter> writeRateLimit = new HashMap<>();

src/main/java/com/amazon/janusgraph/diskstorage/dynamodb/Constants.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2014-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  * Portions copyright Titan: Distributed Graph Database - Copyright 2012 and onwards Aurelius.
  *
  * Licensed under the Apache License, Version 2.0 (the "License").
@@ -37,8 +37,7 @@
  *
  */
 public final class Constants {
-    private Constants() {
-    }
+    private Constants() { }
 //begin adaptation of
 //https://github.com/buka/titan/blob/master/src/main/java/com/thinkaurelius/titan/diskstorage/dynamodb/DynamoDBClient.java#L26
     public static final String JANUSGRAPH_VALUE = "v";
@@ -49,7 +48,7 @@ private Constants() {
     public static final String HEX_PREFIX = "0x";
     public static final String JANUSGRAPH_USER_AGENT = "dynamodb-janusgraph010-storage-backend_1.0.0";
 
-    public static final List<String> REQUIRED_BACKEND_STORES = ImmutableList.of(Backend.EDGESTORE_NAME, //
+    public static final List<String> REQUIRED_BACKEND_STORES = ImmutableList.of(Backend.EDGESTORE_NAME,
         Backend.INDEXSTORE_NAME,
         Backend.SYSTEM_TX_LOG_NAME,
         Backend.SYSTEM_MGMT_LOG_NAME,

src/main/java/com/amazon/janusgraph/diskstorage/dynamodb/DynamoDBStoreManager.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2014-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License").
  * You may not use this file except in compliance with the License.
@@ -222,9 +222,8 @@ public List<KeyRange> getLocalKeyPartition() throws BackendException {
     public Deployment getDeployment() {
         if (client.getDelegate().isEmbedded()) {
             return Deployment.EMBEDDED;
-        } else {
-            return Deployment.REMOTE;
         }
+        return Deployment.REMOTE;
     }
 
     @Override

src/main/java/com/amazon/janusgraph/diskstorage/dynamodb/DynamoDbDelegate.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2014-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License").
  * You may not use this file except in compliance with the License.
@@ -927,9 +927,8 @@ void updatePagesHistogram(final String apiName, final String tableName, final in
     final String getMeterName(final String apiName, final String tableName) {
         if (tableName == null) {
             return String.format("%s.%s", metricsPrefix, apiName);
-        } else {
-            return String.format("%s.%s.%s", metricsPrefix, apiName, tableName);
         }
+        return String.format("%s.%s.%s", metricsPrefix, apiName, tableName);
     }
     final int getMaxConcurrentUsers() {
         return this.maxConcurrentUsers;

src/main/java/com/amazon/janusgraph/diskstorage/dynamodb/DynamoDbStore.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2014-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License").
  * You may not use this file except in compliance with the License.
@@ -159,10 +159,9 @@ private QueryRequest createQueryRequest(final StaticBuffer hashKey, final SliceQ
                 .rangeKey(rangeQuery.getSliceStart(), rangeQuery.getSliceEnd())
                 .build();
 
-        final QueryRequest request = super.createQueryRequest()
+        return super.createQueryRequest()
                .withKeyConditionExpression(keyConditionExpression.getConditionExpression())
                .withExpressionAttributeValues(keyConditionExpression.getAttributeValues());
-        return request;
     }
 
     @Override

src/main/java/com/amazon/janusgraph/diskstorage/dynamodb/ListTablesWorker.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2014-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License").
  * You may not use this file except in compliance with the License.
@@ -25,6 +25,8 @@
 import lombok.Getter;
 
 /**
+ * This class merges multiple pages of table names into one ListTablesResult.
+ *
  * @author Alexander Patrikalakis
  */
 public class ListTablesWorker extends PaginatingTask<ListTablesResult> {

src/main/java/com/amazon/janusgraph/diskstorage/dynamodb/QueryResultWrapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2014-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License").
  * You may not use this file except in compliance with the License.
@@ -23,6 +23,9 @@
 import lombok.RequiredArgsConstructor;
 
 /**
+ * The QueryResultWrapper class associates the JanusGraph key that was used to create the QueryRequest
+ * resulting in the enclosed QueryResult.
+ *
  * @author Alexander Patrikalakis
  */
 @RequiredArgsConstructor

src/main/java/com/amazon/janusgraph/diskstorage/dynamodb/builder/EntryBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * Copyright 2014-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License").
  * You may not use this file except in compliance with the License.
@@ -65,7 +65,7 @@ public List<Entry> buildAll() {
             sliceStartEntry = null;
             sliceEndEntry = null;
         }
-        //TODO(alexp) Arrays.parallelSort(filteredEntries) in JDK 8? Can you switch to java 8?
+        //TODO(amcp) Arrays.parallelSort(filteredEntries)?
         //https://github.com/awslabs/dynamodb-titan-storage-backend/issues/159
         return item.entrySet().stream()
             .map(entry -> {