josh-mckenzie commented on a change in pull request #1213: URL: https://github.com/apache/cassandra/pull/1213#discussion_r722456676
########## File path: src/java/org/apache/cassandra/schema/PartitionDenylist.java ########## @@ -0,0 +1,462 @@ +/* + * 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.cassandra.schema; + +import java.nio.ByteBuffer; +import java.util.HashMap; +import java.util.HashSet; +import java.util.Map; +import java.util.NavigableSet; +import java.util.Set; +import java.util.TreeSet; +import java.util.concurrent.Callable; +import java.util.concurrent.ExecutionException; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.LinkedBlockingQueue; +import java.util.concurrent.ThreadPoolExecutor; +import java.util.concurrent.TimeUnit; + +import com.google.common.cache.CacheBuilder; +import com.google.common.cache.CacheLoader; +import com.google.common.cache.LoadingCache; +import com.google.common.collect.ImmutableSet; +import com.google.common.collect.ImmutableSortedSet; +import com.google.common.util.concurrent.ListenableFuture; +import com.google.common.util.concurrent.ListenableFutureTask; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import org.apache.cassandra.concurrent.ScheduledExecutors; +import org.apache.cassandra.config.DatabaseDescriptor; +import org.apache.cassandra.cql3.UntypedResultSet; +import org.apache.cassandra.db.PartitionPosition; +import org.apache.cassandra.dht.AbstractBounds; +import org.apache.cassandra.dht.Token; +import org.apache.cassandra.exceptions.RequestExecutionException; +import org.apache.cassandra.service.StorageService; +import org.apache.cassandra.service.reads.range.RangeCommands; +import org.apache.cassandra.utils.Hex; +import org.apache.cassandra.utils.Pair; + +import static org.apache.cassandra.cql3.QueryProcessor.process; + +/** + * PartitionDenylist uses the system_distributed.partition_denylist table to maintain a list of denylisted partition keys + * for each keyspace/table. + * + * Keys can be entered manually into the partition_denylist table or via the JMX operation StorageProxyMBean.denylistKey + * + * The denylist is stored as one CQL partition per table, and the denylisted keys are column names in that partition. The denylisted + * keys for each table are cached in memory, and reloaded from the partition_denylist table every 24 hours (default) or when the + * StorageProxyMBean.loadPartitionDenylist is called via JMX. + * + * Concurrency of the cache is provided by the concurrency semantics of the guava LoadingCache. All values (DenylistEntry) are + * immutable collections of keys/tokens which are replaced in whole when the cache refreshes from disk. + */ +public class PartitionDenylist +{ + private static final Logger logger = LoggerFactory.getLogger(PartitionDenylist.class); + public static final String PARTITION_DENYLIST_TABLE = "partition_denylist"; + + private final ExecutorService executor = new ThreadPoolExecutor(2, 2, Long.MAX_VALUE, TimeUnit.SECONDS, new LinkedBlockingQueue<>()); + + /** We effectively don't use our initial empty cache to denylist until the {@link #load()} call which will replace it */ + private volatile LoadingCache<TableId, DenylistEntry> denylist = buildEmptyCache(); + + /** + * Denylist entry is never mutated once constructed, only replaced with a new entry when the cache is refreshed + */ + private static class DenylistEntry + { + public final ImmutableSet<ByteBuffer> keys; + public final ImmutableSortedSet<Token> tokens; + + public DenylistEntry() + { + keys = ImmutableSet.of(); + tokens = ImmutableSortedSet.of(); + } + + public DenylistEntry(final ImmutableSet<ByteBuffer> keys, final ImmutableSortedSet<Token> tokens) + { + this.keys = keys; + this.tokens = tokens; + } + } + + // synchronized on this + private int loadAttempts = 0; + private int loadSuccesses = 0; + + public synchronized int getLoadAttempts() + { + return loadAttempts; + } + public synchronized int getLoadSuccesses() + { + return loadSuccesses; + } + + /** + * Performs initial load of the partition denylist. Should be called at startup and only loads if the operation + * is expected to succeed. If it is not possible to load at call time, a timer is set to retry. + */ + public void initialLoad() + { + if (!DatabaseDescriptor.enablePartitionDenylist()) + return; + + synchronized (this) + { + loadAttempts++; + } + + // Check if there are sufficient nodes to attempt reading all the denylist partitions before issuing the query. + // The pre-check prevents definite range-slice unavailables being marked and triggering an alert. Nodes may still change + // state between the check and the query, but it should significantly reduce the alert volume. + String retryReason = "Insufficient nodes"; + try + { + if (readAllHasSufficientNodes() && load()) + { + return; + } + } + catch (Throwable tr) + { + logger.error("Failed to load partition denylist", tr); + retryReason = "Exception"; + } + + // This path will also be taken on other failures other than UnavailableException, + // but seems like a good idea to retry anyway. + int retryInSeconds = DatabaseDescriptor.getDenylistInitialLoadRetrySeconds(); + logger.info(retryReason + " while loading partition denylist cache. Scheduled retry in {} seconds.", + retryInSeconds); + ScheduledExecutors.optionalTasks.schedule(this::initialLoad, retryInSeconds, TimeUnit.SECONDS); + } + + private boolean readAllHasSufficientNodes() + { + return RangeCommands.sufficientLiveNodesForSelectStar(SystemDistributedKeyspace.PartitionDenylistTable, + DatabaseDescriptor.getDenylistConsistencyLevel()); + } + + /** Helper method as we need to both build cache on initial init but also on reload of cache contents and params */ + private LoadingCache<TableId, DenylistEntry> buildEmptyCache() + { + return CacheBuilder.newBuilder() + .refreshAfterWrite(DatabaseDescriptor.getDenylistRefreshSeconds(), TimeUnit.SECONDS) + .build(new CacheLoader<TableId, DenylistEntry>() + { + @Override + public DenylistEntry load(final TableId tid) throws Exception + { + return getDenylistForTable(tid); + } + + @Override + public ListenableFuture<DenylistEntry> reload(final TableId tid, final DenylistEntry oldValue) + { + ListenableFutureTask<DenylistEntry> task = ListenableFutureTask.create(new Callable<DenylistEntry>() + { + @Override + public DenylistEntry call() + { + final DenylistEntry newEntry = getDenylistForTable(tid); + if (newEntry != null) + return newEntry; + if (oldValue != null) + return oldValue; + return new DenylistEntry(); + } + }); + executor.execute(task); + return task; + } + }); + } + + /** + * We need to fully rebuild a new cache to accommodate deleting items from the denylist and potentially shrinking + * the max allowable size in the list. We do not serve queries out of this denylist until it is populated + * so as not to introduce a window of having a partially filled cache allow denylisted entries. + */ + public boolean load() + { + final long start = System.currentTimeMillis(); + + final Map<TableId, DenylistEntry> allDenylists = getDenylistForAllTables(); + if (allDenylists == null) + return false; + + // On initial load we have the slight overhead of GC'ing our initial empty cache + LoadingCache<TableId, DenylistEntry> newDenylist = buildEmptyCache(); + newDenylist.putAll(allDenylists); + + synchronized (this) + { + loadSuccesses++; + } + denylist = newDenylist; + logger.info("Loaded partition denylist cache in {}ms", System.currentTimeMillis() - start); + return true; + } + + /** + * We expect the caller to confirm that we are working with a valid keyspace and table. Further, we expect the usage + * pattern of this to be one-off key by key, not in a bulk process, so we relead the entire table's deny list entry + * on an addition or removal. + */ + public boolean addKeyToDenylist(final String keyspace, final String table, final ByteBuffer key) + { + if (!isPermitted(keyspace)) + return false; + + final byte[] keyBytes = new byte[key.remaining()]; + key.slice().get(keyBytes); + + final String insert = String.format("INSERT INTO system_distributed.partition_denylist (ks_name, cf_name, key) VALUES ('%s', '%s', 0x%s)", + keyspace, table, Hex.bytesToHex(keyBytes)); + + try + { + process(insert, DatabaseDescriptor.getDenylistConsistencyLevel()); + + // On insert, we refresh the entire table's deny list data. + TableId denyTableId = getTableId(keyspace, table); + denylist.put(denyTableId, getDenylistForTable(getTableId(keyspace, table))); Review comment: So the scenario causing the concern is: 1. A denylist entry is added for PK N. Node A and B receive it, C does not due to unavailability. Quorum is achieved on the denylist change. 2. A query comes in for PK N to Node B 3. ??? This would depend on the CL of the query on PK N right? If you ask for CL.ONE, you're definitely at risk of getting data that's not deny listed correctly for sure. If you query at any other CL, you should get rejection from Node A and C as they received the denylist update and properly reject the query. Our options to tighten this up would be to force CL.ALL for denylist modifications (which we effectively do right now in our codepaths for initialLoad relying on sufficientLiveNodes()...) which introduces availability issues to using the feature, or to for a higher CL for mutations to Keyspaces that have deny-listed keys which isn't really an option. Not updating the data in memory once the denylist CQL mutation succeeds broadens the window of time between the initial expression of intent of an operator (deny access to this key!) data being in CQL and data loading in your denylist cache. While we get the "RF-wide atomicity" property of calling `sufficientLiveNodesForSelectStar` on the cache reload JMX call, it's at the cost of forcing the operator to take another step when they denylist a key as well as not allowing cache refresh unless all nodes in the replica set for the cache are available. Hm... _I think we do have a problem though_. There's no mechanism for refreshing the in-memory cache based on post-hoc adjustments to the underlying system_distributed table (streaming, repair, hints). While we could hook into `Keyspaces.applyInternal `similarly to how we handle view mutations w/`requiresViewUpdate` and then push denylist changes through the PartitionDenylist mechanisms... I'm not sure we should. This puts us squarely in the "denylist cache refresh requires all nodes to be up in order for you to update the denied keys in memory" no matter how we slice it, so maybe the initial implementation of just having it be a two step process for operators (1. adjust CQL/JMX, 2. reload your cache) is the right way after all. Let me think on this a bit more. Interesting problem. -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
