keith-turner commented on a change in pull request #2324: URL: https://github.com/apache/accumulo/pull/2324#discussion_r741452081
########## File path: server/base/src/main/java/org/apache/accumulo/server/conf/store/impl/ZooPropStore.java ########## @@ -0,0 +1,397 @@ +/* + * 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.accumulo.server.conf.store.impl; + +import java.io.IOException; +import java.util.Collection; +import java.util.HashMap; +import java.util.Map; +import java.util.Objects; + +import org.apache.accumulo.core.conf.Property; +import org.apache.accumulo.fate.zookeeper.ZooReaderWriter; +import org.apache.accumulo.fate.zookeeper.ZooUtil; +import org.apache.accumulo.server.ServerContext; +import org.apache.accumulo.server.conf.codec.VersionedPropCodec; +import org.apache.accumulo.server.conf.codec.VersionedProperties; +import org.apache.accumulo.server.conf.store.PropCache; +import org.apache.accumulo.server.conf.store.PropCacheId; +import org.apache.accumulo.server.conf.store.PropChangeListener; +import org.apache.accumulo.server.conf.store.PropStore; +import org.apache.accumulo.server.conf.store.PropStoreException; +import org.apache.zookeeper.KeeperException; +import org.apache.zookeeper.data.Stat; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +public class ZooPropStore implements PropStore, PropChangeListener { + + private final static Logger log = LoggerFactory.getLogger(ZooPropStore.class); + + private final VersionedPropCodec propCodec; + + private final ReadyMonitor zkReadyMon; + + private final ServerContext context; + private final ZooReaderWriter zrw; + private final PropStoreWatcher propStoreWatcher; + private final PropCache cache; + private final PropStoreMetrics cacheMetrics = new PropStoreMetrics(); + + private Map<String,String> fixedProps = null; + + /** + * Create instance using ZooPropStore.Builder + * + * @param context + * the server context + * @param readyMonitor + * coordination utility for ZooKeeper connection status. + * @param propStoreWatcher + * an extended ZooKeeper watcher + */ + private ZooPropStore(final ServerContext context, final ReadyMonitor readyMonitor, + final PropStoreWatcher propStoreWatcher) { + + this.context = context; + this.zrw = context.getZooReaderWriter(); + this.zkReadyMon = readyMonitor; + this.propStoreWatcher = propStoreWatcher; + + this.propCodec = context.getVersionedPropertiesCodec(); + + ZooPropLoader propLoader = new ZooPropLoader(zrw, context.getVersionedPropertiesCodec(), + propStoreWatcher, cacheMetrics); + + cache = new CaffeineCache.Builder(propLoader, cacheMetrics).build(); + + try { + var path = ZooUtil.getRoot(context.getInstanceID()); + if (zrw.exists(path, propStoreWatcher)) { + log.debug("have a ZooKeeper connection"); + zkReadyMon.setReady(); + } else { + throw new IllegalStateException( + "Instance may not have been initialized, root node" + path + " does not exist"); + } + } catch (InterruptedException | KeeperException ex) { + throw new IllegalStateException("Failed to read root node from ZooKeeper", ex); + } + } + + /** + * Create initial system props for the instance. If the node already exists, no action is + * performed. + * + * @param context + * the server context. + * @param initProps + * map of k, v pairs of initial properties. + * @return true if props create, false if the node existed and initialization was skipped. + */ + public synchronized static boolean initSysProps(final ServerContext context, + final Map<String,String> initProps) { + PropCacheId sysPropsId = PropCacheId.forSystem(context.getInstanceID()); + return createInitialProps(context, sysPropsId, initProps); + } + + /** + * Create initial properties if they do not exist. If the node exists, initialization will be + * skipped. + * + * @param context + * the system context + * @param propCacheId + * a prop id + * @param props + * initial properties + * @return true if props create, false if the node existed and initialization was skipped. + */ + public static boolean createInitialProps(final ServerContext context, + final PropCacheId propCacheId, Map<String,String> props) { + + try { + ZooReaderWriter zrw = context.getZooReaderWriter(); + if (zrw.exists(propCacheId.getPath())) { + return false; + } + VersionedProperties vProps = new VersionedProperties(props); + return zrw.putPersistentData(propCacheId.getPath(), + context.getVersionedPropertiesCodec().toBytes(vProps), ZooUtil.NodeExistsPolicy.FAIL); + } catch (InterruptedException ex) { + Thread.currentThread().interrupt(); + throw new IllegalStateException("Interrupted creating node " + propCacheId, ex); + } catch (Exception ex) { + throw new IllegalStateException("Failed to create node " + propCacheId, ex); + } + } + + public PropStoreMetrics getMetrics() { + return cacheMetrics; + } + + // TODO - evaluate returning the props instead of boolean. + @Override + public boolean create(PropCacheId propCacheId, Map<String,String> props) + throws PropStoreException { + + VersionedProperties vProps = new VersionedProperties(props); + + try { + + var path = propCacheId.getPath(); + if (!zrw.putPersistentData(path, propCodec.toBytes(vProps), ZooUtil.NodeExistsPolicy.FAIL)) { + return false; + } + + Stat stat = zrw.getStatus(path, propStoreWatcher); + + if (stat.getVersion() != vProps.getNextVersion()) { + throw new PropStoreException( + "Invalid data version on create, received " + stat.getVersion(), + new IllegalStateException()); + } + + return true; + + } catch (IOException | KeeperException | InterruptedException ex) { + throw new PropStoreException("Failed to serialize properties for " + propCacheId, ex); + } + } + + @Override + public VersionedProperties get(final PropCacheId propCacheId) throws PropStoreException { + try { + + checkZkConnection(); // if ZK not connected, block, do not just return a cached value. + propStoreWatcher.registerListener(propCacheId, this); + return cache.get(propCacheId); + + } catch (Exception ex) { + throw new PropStoreException("read from prop store get() failed for: " + propCacheId, ex); + } + } + + @Override + public boolean putAll(final PropCacheId propCacheId, final Map<String,String> props) + throws PropStoreException { + + try { + Review comment: For the case of two thread setting the same thing concurrently we want to achieve the same result as them running serially in any order. For the concurrent case if one succeeds and the other fails and retries, then we should get the same result as them running serially. For example the following ``` Thread-1 reads the current props and stat from ZK Thread-2 reads the current props and stat from ZK Thread-1 modifies the props in memory to set A=x,B=z Thread-2 modified the props in memory to set A=y,C=q Thread-1 successfully writes the modified props to ZK Thread-2 fails to write the props to ZK because the version does not match what it read Thread-2 reads the current props and stat from ZK Thread-2 modifies the props to set A=y,C=q Thread-2 successfully writes the modified props to ZK ``` The above sequence of events should result in the props in ZK being `A=y,B=z,C=q` which is the same as what we would see if there was no concurrency in the following set of events. Neither one of these outcomes are surprising. ``` Thread-1 reads the current props and stat from ZK Thread-1 modifies the props in memory to set A=x,B=z Thread-1 successfully writes the modified props to ZK Thread-2 reads the current props and stat from ZK Thread-2 modifies the props in memory to set A=y,C=q Thread-2 successfully writes the modified props to ZK ``` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
