findepi commented on code in PR #10691:
URL: https://github.com/apache/iceberg/pull/10691#discussion_r1677652693
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core/src/main/java/org/apache/iceberg/util/ParallelIterable.java:
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@@ -20,65 +20,69 @@
import java.io.Closeable;
import java.io.IOException;
+import java.util.ArrayDeque;
+import java.util.Deque;
import java.util.Iterator;
import java.util.NoSuchElementException;
+import java.util.Optional;
+import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
-import org.apache.iceberg.exceptions.RuntimeIOException;
+import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.iceberg.io.CloseableGroup;
import org.apache.iceberg.io.CloseableIterable;
import org.apache.iceberg.io.CloseableIterator;
import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
import org.apache.iceberg.relocated.com.google.common.collect.Iterables;
+import org.apache.iceberg.relocated.com.google.common.io.Closer;
public class ParallelIterable<T> extends CloseableGroup implements
CloseableIterable<T> {
+
+ private static final int DEFAULT_MAX_QUEUE_SIZE = 10_000;
+
private final Iterable<? extends Iterable<T>> iterables;
private final ExecutorService workerPool;
+ // Bound for number of items in the queue to limit memory consumption
+ // even in the case when input iterables are large.
+ private final int approximateMaxQueueSize;
+
public ParallelIterable(Iterable<? extends Iterable<T>> iterables,
ExecutorService workerPool) {
- this.iterables = iterables;
- this.workerPool = workerPool;
+ this(iterables, workerPool, DEFAULT_MAX_QUEUE_SIZE);
+ }
+
+ public ParallelIterable(
+ Iterable<? extends Iterable<T>> iterables,
+ ExecutorService workerPool,
+ int approximateMaxQueueSize) {
+ this.iterables = Preconditions.checkNotNull(iterables, "Input iterables
cannot be null");
+ this.workerPool = Preconditions.checkNotNull(workerPool, "Worker pool
cannot be null");
+ this.approximateMaxQueueSize = approximateMaxQueueSize;
}
@Override
public CloseableIterator<T> iterator() {
- ParallelIterator<T> iter = new ParallelIterator<>(iterables, workerPool);
+ ParallelIterator<T> iter =
+ new ParallelIterator<>(iterables, workerPool, approximateMaxQueueSize);
addCloseable(iter);
return iter;
}
private static class ParallelIterator<T> implements CloseableIterator<T> {
- private final Iterator<Runnable> tasks;
+ private final Iterator<Task<T>> tasks;
+ private final Deque<Task<T>> yieldedTasks = new ArrayDeque<>();
Review Comment:
`Iterator` cannot be reasonably consumed by multiple consumers, so the only
real concurrency is for filling the queue. however, ParallelItetator has the
safegurads - the next and hasNext are synchronized.
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