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Lattice Cache - Caching Just Data Implementation #2619

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merged 6 commits into from
Sep 28, 2023
Merged

Lattice Cache - Caching Just Data Implementation #2619

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e017b05
Data cache implementation
Sep 19, 2023
0b47a24
Data cache
Sep 19, 2023
bfeca3b
Separate thread for event changes. Hasmap computeifabsent
Sep 21, 2023
276f3b1
Remove lazy caching. Prepopulate in the beginning, return null if dat…
Sep 24, 2023
7355b82
Addressed comments
Sep 26, 2023
d1f01df
Population of cache
Sep 27, 2023
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2 changes: 1 addition & 1 deletion meta-client/src/main/java/org/apache/helix/metaclient/api/MetaClientCacheInterface.java
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@ class TrieNode {

private final String _nodeKey;

TrieNode(String path, String nodeKey) {
public TrieNode(String path, String nodeKey) {
_path = path;
_nodeKey = nodeKey;
_children = new HashMap<>();
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5 changes: 0 additions & 5 deletions meta-client/src/main/java/org/apache/helix/metaclient/factories/MetaClientCacheConfig.java
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Expand Up @@ -25,13 +25,11 @@ public class MetaClientCacheConfig {
private final String _rootEntry;
private boolean _cacheData = false;
private boolean _cacheChildren = false;
private boolean _lazyCaching = true;

public MetaClientCacheConfig(String rootEntry, boolean cacheData, boolean cacheChildren, boolean lazyCaching) {
_rootEntry = rootEntry;
_cacheData = cacheData;
_cacheChildren = cacheChildren;
_lazyCaching = lazyCaching;
}

public String getRootEntry() {
Expand All @@ -46,7 +44,4 @@ public boolean getCacheChildren() {
return _cacheChildren;
}

public boolean getLazyCaching() {
return _lazyCaching;
}
}
25 changes: 11 additions & 14 deletions meta-client/src/main/java/org/apache/helix/metaclient/factories/MetaClientFactory.java
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Expand Up @@ -40,13 +40,7 @@ public MetaClientInterface getMetaClient(MetaClientConfig config) {
throw new IllegalArgumentException("MetaClientConfig cannot be null.");
}
if (MetaClientConfig.StoreType.ZOOKEEPER.equals(config.getStoreType())) {
ZkMetaClientConfig zkMetaClientConfig = new ZkMetaClientConfig.ZkMetaClientConfigBuilder().
setConnectionAddress(config.getConnectionAddress())
.setMetaClientReconnectPolicy(config.getMetaClientReconnectPolicy())
.setConnectionInitTimeoutInMillis(config.getConnectionInitTimeoutInMillis())
.setSessionTimeoutInMillis(config.getSessionTimeoutInMillis())
.build();
return new ZkMetaClientFactory().getMetaClient(zkMetaClientConfig);
return new ZkMetaClientFactory().getMetaClient(createZkMetaClientConfig(config));
}
return null;
}
Expand All @@ -56,14 +50,17 @@ public MetaClientCacheInterface getMetaClientCache(MetaClientConfig config, Meta
throw new IllegalArgumentException("MetaClientConfig cannot be null.");
}
if (MetaClientConfig.StoreType.ZOOKEEPER.equals(config.getStoreType())) {
ZkMetaClientConfig zkMetaClientConfig = new ZkMetaClientConfig.ZkMetaClientConfigBuilder().
setConnectionAddress(config.getConnectionAddress())
.setMetaClientReconnectPolicy(config.getMetaClientReconnectPolicy())
.setConnectionInitTimeoutInMillis(config.getConnectionInitTimeoutInMillis())
.setSessionTimeoutInMillis(config.getSessionTimeoutInMillis())
.build();
return new ZkMetaClientFactory().getMetaClientCache(zkMetaClientConfig, cacheConfig);
return new ZkMetaClientFactory().getMetaClientCache(createZkMetaClientConfig(config), cacheConfig);
}
return null;
}

private ZkMetaClientConfig createZkMetaClientConfig(MetaClientConfig config) {
return new ZkMetaClientConfig.ZkMetaClientConfigBuilder().
setConnectionAddress(config.getConnectionAddress())
.setMetaClientReconnectPolicy(config.getMetaClientReconnectPolicy())
.setConnectionInitTimeoutInMillis(config.getConnectionInitTimeoutInMillis())
.setSessionTimeoutInMillis(config.getSessionTimeoutInMillis())
.build();
}
}
124 changes: 106 additions & 18 deletions meta-client/src/main/java/org/apache/helix/metaclient/impl/zk/ZkMetaClientCache.java
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Expand Up @@ -21,31 +21,33 @@

import org.apache.helix.metaclient.api.ChildChangeListener;
import org.apache.helix.metaclient.api.MetaClientCacheInterface;
import org.apache.helix.metaclient.datamodel.DataRecord;
import org.apache.helix.metaclient.exception.MetaClientException;
import org.apache.helix.metaclient.factories.MetaClientCacheConfig;
import org.apache.helix.metaclient.factories.MetaClientConfig;
import org.apache.helix.metaclient.impl.zk.adapter.ChildListenerAdapter;
import org.apache.helix.metaclient.impl.zk.factory.ZkMetaClientConfig;
import org.apache.helix.metaclient.impl.zk.factory.ZkMetaClientFactory;
import org.apache.helix.metaclient.recipes.lock.LockInfoSerializer;
import org.apache.helix.zookeeper.zkclient.ZkClient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ZkMetaClientCache<T> extends ZkMetaClient<T> implements MetaClientCacheInterface<T> {

private Map<String, DataRecord> _dataCacheMap;
private ConcurrentHashMap<String, T> _dataCacheMap;
private final String _rootEntry;
private TrieNode _childrenCacheTree;
private ChildChangeListener _eventListener;
private boolean _cacheData;
private boolean _cacheChildren;
private boolean _lazyCaching;
private static final Logger LOG = LoggerFactory.getLogger(ZkMetaClientCache.class);
private ZkClient _cacheClient;
private ExecutorService executor;
private final CountDownLatch latch = new CountDownLatch(1);
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/**
* Constructor for ZkMetaClientCache.
Expand All @@ -56,19 +58,39 @@ public ZkMetaClientCache(ZkMetaClientConfig config, MetaClientCacheConfig cacheC
super(config);
_cacheClient = getZkClient();
_rootEntry = cacheConfig.getRootEntry();
_lazyCaching = cacheConfig.getLazyCaching();
_cacheData = cacheConfig.getCacheData();
_cacheChildren = cacheConfig.getCacheChildren();

if (_cacheData) {
_dataCacheMap = new ConcurrentHashMap<>();
}
if (_cacheChildren) {
_childrenCacheTree = new TrieNode(_rootEntry, null);
}
}

/**
* Get data for a given key.
* If datacache is enabled, will fetch for cache. If it doesn't exist
* returns null (for when initial populating cache is in progress).
* @param key key to identify the entry
* @return data for the key
*/
@Override
public Stat exists(String key) {
throw new MetaClientException("Not implemented yet.");
public T get(final String key) {
if (_cacheData) {
return getDataCacheMap().get(key);
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shall we differentiate if key is not in ZK, or it is in ZK but not populated to cache yet?

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I am not too sure how to do this without pinging zookeeper. If it's not populated yet how do we know if it doesn't actually exist in zookeeper or it's being populated without checking zk?

}
return _cacheClient.readData(key, true);
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}

@Override
public T get(final String key) {
throw new MetaClientException("Not implemented yet.");
public List<T> get(List<String> keys) {
List<T> dataList = new ArrayList<>();
for (String key : keys) {
dataList.add(get(key));
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same as above.

}
return dataList;
}

@Override
Expand All @@ -81,14 +103,80 @@ public int countDirectChildren(final String key) {
throw new MetaClientException("Not implemented yet.");
}

@Override
public List<T> get(List<String> keys) {
throw new MetaClientException("Not implemented yet.");
private void populateAllCache() {
if (_cacheData) {
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try {
List<String> children = _cacheClient.getChildren(_rootEntry);
for (String child : children) {
String childPath = _rootEntry + "/" + child;
T dataRecord = _cacheClient.readData(childPath, true);
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getDataCacheMap().put(childPath, dataRecord);
}
} catch (Exception e) {
// Ignore
}
}
}

@Override
public List<Stat> exists(List<String> keys) {
throw new MetaClientException("Not implemented yet.");
private void handleCacheUpdate(String path, ChildChangeListener.ChangeType changeType) {
waitForPopulateAllCache();
switch (changeType) {
case ENTRY_CREATED:
// Not implemented yet.
modifyDataInCache(path, false);
break;
case ENTRY_DELETED:
// Not implemented yet.
modifyDataInCache(path, true);
break;
case ENTRY_DATA_CHANGE:
modifyDataInCache(path, false);
break;
default:
LOG.error("Unknown change type: " + changeType);
}
}

private void waitForPopulateAllCache() {
try {
latch.await();
} catch (InterruptedException e) {
throw new MetaClientException("Interrupted while waiting for cache to populate.", e);
}
}

private void modifyDataInCache(String path, Boolean isDelete) {
if (_cacheData) {
if (isDelete) {
getDataCacheMap().remove(path);
} else {
T dataRecord = _cacheClient.readData(path, true);
getDataCacheMap().put(path, dataRecord);
}
}
}

public ConcurrentHashMap<String, T> getDataCacheMap() {
return _dataCacheMap;
}

public TrieNode getChildrenCacheTree() {
return _childrenCacheTree;
}

/**
* Connect to the underlying ZkClient.
*/
@Override
public void connect() {
super.connect();
_eventListener = this::handleCacheUpdate;
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executor = Executors.newSingleThreadExecutor();
executor.execute(() -> {
_cacheClient.subscribePersistRecursiveListener(_rootEntry, new ChildListenerAdapter(_eventListener));
});
populateAllCache();
// Notify the latch that cache is populated.
latch.countDown();
}
}
85 changes: 73 additions & 12 deletions meta-client/src/test/java/org/apache/helix/metaclient/impl/zk/TestZkMetaClientCache.java
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Expand Up @@ -19,39 +19,100 @@
* under the License.
*/


import org.apache.helix.metaclient.factories.MetaClientCacheConfig;
import org.apache.helix.metaclient.impl.zk.factory.ZkMetaClientConfig;
import org.testng.Assert;
import org.testng.annotations.Test;

import java.util.ArrayList;
import java.util.List;

public class TestZkMetaClientCache extends ZkMetaClientTestBase {
private static final String PATH = "/Cache";
private static final String DATA_PATH = "/data";
private static final String DATA_VALUE = "testData";

@Test
public void testCreateClient() {
final String key = "/TestZkMetaClientCache_testCreate";
try (ZkMetaClient<String> zkMetaClientCache = createZkMetaClientCache()) {
final String key = "/testCreate";
try (ZkMetaClientCache<String> zkMetaClientCache = createZkMetaClientCacheLazyCaching(key)) {
zkMetaClientCache.connect();
// Perform some random non-read operation
zkMetaClientCache.create(key, ENTRY_STRING_VALUE);
}
}

@Test
public void testCacheDataUpdates() {
final String key = "/testCacheDataUpdates";
try (ZkMetaClientCache<String> zkMetaClientCache = createZkMetaClientCacheLazyCaching(key)) {
zkMetaClientCache.connect();
zkMetaClientCache.create(key, "test");
zkMetaClientCache.create(key + DATA_PATH, DATA_VALUE);

// Get data for DATA_PATH and cache it
String data = zkMetaClientCache.get(key + DATA_PATH);
Assert.assertEquals(data, zkMetaClientCache.getDataCacheMap().get(key + DATA_PATH));

// Update data for DATA_PATH
String newData = zkMetaClientCache.update(key + DATA_PATH, currentData -> currentData + "1");

// Verify that cached data is updated. Might take some time
for (int i = 0; i < 10; i++) {
if (zkMetaClientCache.getDataCacheMap().get(key + DATA_PATH).equals(newData)) {
break;
}
Thread.sleep(1000);
}
Assert.assertEquals(newData, zkMetaClientCache.getDataCacheMap().get(key + DATA_PATH));

zkMetaClientCache.delete(key + DATA_PATH);
// Verify that cached data is updated. Might take some time
for (int i = 0; i < 10; i++) {
if (zkMetaClientCache.getDataCacheMap().get(key + DATA_PATH) == null) {
break;
}
Thread.sleep(1000);
}
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}

@Test
public void testBatchGet() {
final String key = "/testBatchGet";
try (ZkMetaClientCache<String> zkMetaClientCache = createZkMetaClientCacheLazyCaching(key)) {
zkMetaClientCache.connect();
zkMetaClientCache.create(key, "test");
zkMetaClientCache.create(key + DATA_PATH, DATA_VALUE);

ArrayList<String> keys = new ArrayList<>();
keys.add(key);
keys.add(key + DATA_PATH);

ArrayList<String> values = new ArrayList<>();
values.add("test");
values.add(DATA_VALUE);

try {
//Perform some read operation - should fail.
// TODO: Remove this once implemented.
zkMetaClientCache.get(key);
Assert.fail("Should have failed with non implemented yet.");
} catch (Exception ignored) {
for (int i = 0; i < 10; i++) {
// Get data for DATA_PATH and cache it
List<String> data = zkMetaClientCache.get(keys);
if (data.equals(values)) {
break;
}
Thread.sleep(1000);
}
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}

protected static ZkMetaClientCache<String> createZkMetaClientCache() {
protected static ZkMetaClientCache<String> createZkMetaClientCacheLazyCaching(String rootPath) {
ZkMetaClientConfig config =
new ZkMetaClientConfig.ZkMetaClientConfigBuilder().setConnectionAddress(ZK_ADDR)
//.setZkSerializer(new TestStringSerializer())
.build();
MetaClientCacheConfig cacheConfig = new MetaClientCacheConfig(PATH, true, true, true);
MetaClientCacheConfig cacheConfig = new MetaClientCacheConfig(rootPath, true, true, true);
return new ZkMetaClientCache<>(config, cacheConfig);
}
}