BSA for integration test (#2256)

Supports the full blocklist download cycle (download, diffing, diff-apply, and order-status reporting) and the refreshing of unblockable domains.

Submitted due to tight deadline. We will conduct post-submit review and refactoring.

common/src/main/java/google/registry/util/BatchedStreams.java

@@ -0,0 +1,43 @@
+// Copyright 2023 The Nomulus Authors. 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.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.util;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.collect.Iterators.partition;
+import static com.google.common.collect.Iterators.transform;
+import static com.google.common.collect.Streams.stream;
+import static java.lang.Math.min;
+
+import com.google.common.collect.ImmutableList;
+import java.util.stream.Stream;
+
+/** Utilities for breaking up a {@link Stream} into batches. */
+public final class BatchedStreams {
+
+  static final int MAX_BATCH = 1024 * 1024;
+
+  private BatchedStreams() {}
+
+  /**
+   * Transform a flat {@link Stream} into a {@code Stream} of batches.
+   *
+   * <p>Closing the returned stream does not close the original stream.
+   */
+  public static <T> Stream<ImmutableList<T>> toBatches(Stream<T> stream, int batchSize) {
+    checkArgument(batchSize > 0, "batchSize must be a positive integer.");
+    return stream(
+        transform(partition(stream.iterator(), min(MAX_BATCH, batchSize)), ImmutableList::copyOf));
+  }
+}

common/src/test/java/google/registry/util/BatchedStreamsTest.java

@@ -0,0 +1,65 @@
+// Copyright 2023 The Nomulus Authors. 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.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.util;
+
+import static com.google.common.truth.Truth.assertThat;
+import static google.registry.util.BatchedStreams.toBatches;
+import static java.util.stream.Collectors.counting;
+import static java.util.stream.Collectors.groupingBy;
+import static org.junit.Assert.assertThrows;
+
+import com.google.common.collect.ImmutableList;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.Test;
+
+/** Unit tests for {@link BatchedStreams}. */
+public class BatchedStreamsTest {
+
+  @Test
+  void invalidBatchSize() {
+    assertThat(assertThrows(IllegalArgumentException.class, () -> toBatches(Stream.of(), 0)))
+        .hasMessageThat()
+        .contains("must be a positive integer");
+  }
+
+  @Test
+  void batch_success() {
+    // 900_002 elements -> 900 1K-batches + 1 2-element-batch
+    Stream<Integer> data = IntStream.rangeClosed(0, 900_001).boxed();
+    assertThat(
+            toBatches(data, 1000).map(ImmutableList::size).collect(groupingBy(x -> x, counting())))
+        .containsExactly(1000, 900L, 2, 1L);
+  }
+
+  @Test
+  void batch_partialBatch() {
+    Stream<Integer> data = Stream.of(1, 2, 3);
+    assertThat(
+            toBatches(data, 1000).map(ImmutableList::size).collect(groupingBy(x -> x, counting())))
+        .containsExactly(3, 1L);
+  }
+
+  @Test
+  void batch_truncateBatchSize() {
+    // 2M elements -> 2 1M-batches despite the user-specified 2M batch size.
+    Stream<Integer> data = IntStream.range(0, 1024 * 2048).boxed();
+    assertThat(
+            toBatches(data, 2_000_000)
+                .map(ImmutableList::size)
+                .collect(groupingBy(x -> x, counting())))
+        .containsExactly(1024 * 1024, 2L);
+  }
+}