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* 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
*
* 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 org.apache.hcatalog.common;
import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.RemovalListener;
import com.google.common.cache.RemovalNotification;
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.hadoop.hive.conf.HiveConf;
import org.apache.hadoop.hive.metastore.HiveMetaStoreClient;
import org.apache.hadoop.hive.metastore.api.MetaException;
import org.apache.hadoop.hive.shims.ShimLoader;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.thrift.TException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.security.auth.login.LoginException;
import java.io.IOException;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
/**
* A thread safe time expired cache for HiveMetaStoreClient
* @deprecated Use/modify {@link org.apache.hive.hcatalog.common.HiveClientCache} instead
*/
class HiveClientCache {
final private Cache hiveCache;
private static final Logger LOG = LoggerFactory.getLogger(HiveClientCache.class);
private final int timeout;
// This lock is used to make sure removalListener won't close a client that is being contemplated for returning by get()
private final Object CACHE_TEARDOWN_LOCK = new Object();
private static final AtomicInteger nextId = new AtomicInteger(0);
// Since HiveMetaStoreClient is not threadsafe, hive clients are not shared across threads.
// Thread local variable containing each thread's unique ID, is used as one of the keys for the cache
// causing each thread to get a different client even if the hiveConf is same.
private static final ThreadLocal threadId =
new ThreadLocal() {
@Override
protected Integer initialValue() {
return nextId.getAndIncrement();
}
};
private int getThreadId() {
return threadId.get();
}
/**
* @param timeout the length of time in seconds after a client is created that it should be automatically removed
*/
public HiveClientCache(final int timeout) {
this.timeout = timeout;
RemovalListener removalListener =
new RemovalListener() {
public void onRemoval(RemovalNotification notification) {
CacheableHiveMetaStoreClient hiveMetaStoreClient = notification.getValue();
if (hiveMetaStoreClient != null) {
synchronized (CACHE_TEARDOWN_LOCK) {
hiveMetaStoreClient.setExpiredFromCache();
hiveMetaStoreClient.tearDownIfUnused();
}
}
}
};
hiveCache = CacheBuilder.newBuilder()
.expireAfterWrite(timeout, TimeUnit.SECONDS)
.removalListener(removalListener)
.build();
// Add a shutdown hook for cleanup, if there are elements remaining in the cache which were not cleaned up.
// This is the best effort approach. Ignore any error while doing so. Notice that most of the clients
// would get cleaned up via either the removalListener or the close() call, only the active clients
// that are in the cache or expired but being used in other threads wont get cleaned. The following code will only
// clean the active cache ones. The ones expired from cache but being hold by other threads are in the mercy
// of finalize() being called.
Thread cleanupHiveClientShutdownThread = new Thread() {
@Override
public void run() {
LOG.debug("Cleaning up hive client cache in ShutDown hook");
closeAllClientsQuietly();
}
};
Runtime.getRuntime().addShutdownHook(cleanupHiveClientShutdownThread);
}
/**
* Note: This doesn't check if they are being used or not, meant only to be called during shutdown etc.
*/
void closeAllClientsQuietly() {
try {
ConcurrentMap elements = hiveCache.asMap();
for (CacheableHiveMetaStoreClient cacheableHiveMetaStoreClient : elements.values()) {
cacheableHiveMetaStoreClient.tearDown();
}
} catch (Exception e) {
LOG.warn("Clean up of hive clients in the cache failed. Ignored", e);
}
}
public void cleanup() {
hiveCache.cleanUp();
}
/**
* Returns a cached client if exists or else creates one, caches and returns it. It also checks that the client is
* healthy and can be reused
* @param hiveConf
* @return the hive client
* @throws MetaException
* @throws IOException
* @throws LoginException
*/
public HiveMetaStoreClient get(final HiveConf hiveConf) throws MetaException, IOException, LoginException {
final HiveClientCacheKey cacheKey = HiveClientCacheKey.fromHiveConf(hiveConf, getThreadId());
CacheableHiveMetaStoreClient hiveMetaStoreClient = null;
// the hmsc is not shared across threads. So the only way it could get closed while we are doing healthcheck
// is if removalListener closes it. The synchronization takes care that removalListener won't do it
synchronized (CACHE_TEARDOWN_LOCK) {
hiveMetaStoreClient = getOrCreate(cacheKey);
hiveMetaStoreClient.acquire();
}
if (!hiveMetaStoreClient.isOpen()) {
synchronized (CACHE_TEARDOWN_LOCK) {
hiveCache.invalidate(cacheKey);
hiveMetaStoreClient.close();
hiveMetaStoreClient = getOrCreate(cacheKey);
hiveMetaStoreClient.acquire();
}
}
return hiveMetaStoreClient;
}
/**
* Return from cache if exists else create/cache and return
* @param cacheKey
* @return
* @throws IOException
* @throws MetaException
* @throws LoginException
*/
private CacheableHiveMetaStoreClient getOrCreate(final HiveClientCacheKey cacheKey) throws IOException, MetaException, LoginException {
try {
return hiveCache.get(cacheKey, new Callable() {
@Override
public CacheableHiveMetaStoreClient call() throws MetaException {
return new CacheableHiveMetaStoreClient(cacheKey.getHiveConf(), timeout);
}
});
} catch (ExecutionException e) {
Throwable t = e.getCause();
if (t instanceof IOException) {
throw (IOException) t;
} else if (t instanceof MetaException) {
throw (MetaException) t;
} else if (t instanceof LoginException) {
throw (LoginException) t;
} else {
throw new IOException("Error creating hiveMetaStoreClient", t);
}
}
}
/**
* A class to wrap HiveConf and expose equality based only on UserGroupInformation and the metaStoreURIs.
* This becomes the key for the cache and this way the same HiveMetaStoreClient would be returned if
* UserGroupInformation and metaStoreURIs are same. This function can evolve to express
* the cases when HiveConf is different but the same hiveMetaStoreClient can be used
*/
public static class HiveClientCacheKey {
final private String metaStoreURIs;
final private UserGroupInformation ugi;
final private HiveConf hiveConf;
final private int threadId;
private HiveClientCacheKey(HiveConf hiveConf, final int threadId) throws IOException, LoginException {
this.metaStoreURIs = hiveConf.getVar(HiveConf.ConfVars.METASTOREURIS);
ugi = ShimLoader.getHadoopShims().getUGIForConf(hiveConf);
this.hiveConf = hiveConf;
this.threadId = threadId;
}
public static HiveClientCacheKey fromHiveConf(HiveConf hiveConf, final int threadId) throws IOException, LoginException {
return new HiveClientCacheKey(hiveConf, threadId);
}
public HiveConf getHiveConf() {
return hiveConf;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
HiveClientCacheKey that = (HiveClientCacheKey) o;
return new EqualsBuilder().
append(this.metaStoreURIs,
that.metaStoreURIs).
append(this.ugi, that.ugi).
append(this.threadId, that.threadId).isEquals();
}
@Override
public int hashCode() {
return new HashCodeBuilder().
append(metaStoreURIs).
append(ugi).
append(threadId).toHashCode();
}
}
/**
* Add # of current users on HiveMetaStoreClient, so that the client can be cleaned when no one is using it.
*/
public static class CacheableHiveMetaStoreClient extends HiveMetaStoreClient {
private AtomicInteger users = new AtomicInteger(0);
private volatile boolean expiredFromCache = false;
private boolean isClosed = false;
private final long expiryTime;
private static final int EXPIRY_TIME_EXTENSION_IN_MILLIS = 60 * 1000;
public CacheableHiveMetaStoreClient(final HiveConf conf, final int timeout) throws MetaException {
super(conf);
// Extend the expiry time with some extra time on top of guava expiry time to make sure
// that items closed() are for sure expired and would never be returned by guava.
this.expiryTime = System.currentTimeMillis() + timeout * 1000 + EXPIRY_TIME_EXTENSION_IN_MILLIS;
}
private void acquire() {
users.incrementAndGet();
}
private void release() {
users.decrementAndGet();
}
public void setExpiredFromCache() {
expiredFromCache = true;
}
public boolean isClosed() {
return isClosed;
}
/**
* Make a call to hive meta store and see if the client is still usable. Some calls where the user provides
* invalid data renders the client unusable for future use (example: create a table with very long table name)
* @return
*/
protected boolean isOpen() {
try {
// Look for an unlikely database name and see if either MetaException or TException is thrown
this.getDatabases("NonExistentDatabaseUsedForHealthCheck");
} catch (TException e) {
return false;
}
return true;
}
/**
* Decrement the user count and piggyback this to set expiry flag as well, then teardown(), if conditions are met.
* This *MUST* be called by anyone who uses this client.
*/
@Override
public void close() {
release();
if (System.currentTimeMillis() >= expiryTime)
setExpiredFromCache();
tearDownIfUnused();
}
/**
* Tear down only if
* 1. There are no active user
* 2. It has expired from the cache
*/
private void tearDownIfUnused() {
if (users.get() == 0 && expiredFromCache) {
this.tearDown();
}
}
/**
* Close if not closed already
*/
protected synchronized void tearDown() {
try {
if (!isClosed) {
super.close();
}
isClosed = true;
} catch (Exception e) {
LOG.warn("Error closing hive metastore client. Ignored.", e);
}
}
/**
* Last effort to clean up, may not even get called.
* @throws Throwable
*/
@Override
protected void finalize() throws Throwable {
try {
this.tearDown();
} finally {
super.finalize();
}
}
}
}
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