Github user hnfgns commented on a diff in the pull request:
https://github.com/apache/drill/pull/374#discussion_r52954081
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/coord/zk/ZkEphemeralStore.java
---
@@ -0,0 +1,145 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * 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 org.apache.drill.exec.coord.zk;
+
+import java.io.IOException;
+import java.util.Iterator;
+import java.util.Map;
+
+import javax.annotation.Nullable;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Function;
+import com.google.common.collect.Iterators;
+import com.google.common.collect.Lists;
+import org.apache.curator.framework.CuratorFramework;
+import
org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
+import org.apache.drill.common.collections.ImmutableEntry;
+import org.apache.drill.common.exceptions.DrillRuntimeException;
+import org.apache.drill.exec.coord.store.BaseTransientStore;
+import org.apache.drill.exec.coord.store.TransientStoreConfig;
+import org.apache.drill.exec.coord.store.TransientStoreEvent;
+import org.apache.drill.exec.serialization.InstanceSerializer;
+import org.apache.zookeeper.CreateMode;
+
+public class ZkEphemeralStore<V> extends BaseTransientStore<V> {
+
+ @VisibleForTesting
+ protected final PathChildrenCacheListener dispatcher = new
EventDispatcher<>(this);
+ private final ZookeeperClient client;
+
+ public ZkEphemeralStore(final TransientStoreConfig<V> config, final
CuratorFramework curator) {
+ super(config);
+ this.client = new ZookeeperClient(curator, PathUtils.join("/",
config.getName()), CreateMode.EPHEMERAL);
+ }
+
+ public void start() throws Exception {
+ getClient().getCache().getListenable().addListener(dispatcher);
+ getClient().start();
+ }
+
+ protected ZookeeperClient getClient() {
+ return client;
+ }
+
+ @Override
+ public V get(final String key) {
+ final byte[] bytes = getClient().get(key);
+ if (bytes == null) {
+ return null;
+ }
+ try {
+ return config.getSerializer().deserialize(bytes);
+ } catch (final IOException e) {
+ throw new DrillRuntimeException(String.format("unable to deserialize
value at %s", key), e);
+ }
+ }
+
+ @Override
+ public V put(final String key, final V value) {
+ final InstanceSerializer<V> serializer = config.getSerializer();
+ try {
+ final byte[] old = getClient().get(key);
+ final byte[] bytes = serializer.serialize(value);
+ getClient().put(key, bytes);
+ if (old == null) {
+ return null;
+ }
+ return serializer.deserialize(old);
+ } catch (final IOException e) {
+ throw new DrillRuntimeException(String.format("unable to
de/serialize value of type %s", value.getClass()), e);
+ }
+ }
+
+ @Override
+ public V putIfAbsent(final String key, final V value) {
+ final V old = get(key);
+ if (old == null) {
+ try {
+ final byte[] bytes = config.getSerializer().serialize(value);
+ getClient().put(key, bytes);
+ } catch (final IOException e) {
+ throw new DrillRuntimeException(String.format("unable to serialize
value of type %s", value.getClass()), e);
+ }
+ }
+ return old;
+ }
+
+ @Override
+ public V remove(final String key) {
+ final V existing = get(key);
+ if (existing != null) {
+ getClient().delete(key);
+ }
+ return existing;
+ }
+
+ @Override
+ public Iterator<Map.Entry<String, V>> entries() {
+ return Iterators.transform(getClient().entries(), new
Function<Map.Entry<String, byte[]>, Map.Entry<String, V>>() {
+ @Nullable
+ @Override
+ public Map.Entry<String, V> apply(@Nullable Map.Entry<String,
byte[]> input) {
+ try {
+ final V value =
config.getSerializer().deserialize(input.getValue());
+ return new ImmutableEntry<>(input.getKey(), value);
+ } catch (final IOException e) {
+ throw new DrillRuntimeException(String.format("unable to
deserialize value at key %s", input.getKey()), e);
+ }
+ }
+ });
+ }
+
+ @Override
+ public int size() {
+ return Lists.newArrayList(entries()).size();
--- End diff --
yep. made it so that it avoids extraneous deserialization step.
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