Java tutorial
/* * 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.service; import java.net.InetAddress; import java.nio.ByteBuffer; import java.util.ArrayList; import java.util.Collections; import java.util.List; import java.util.concurrent.TimeUnit; import com.google.common.collect.Iterables; import org.apache.cassandra.db.*; import org.apache.cassandra.db.columniterator.IdentityQueryFilter; import org.apache.cassandra.db.filter.IDiskAtomFilter; import org.apache.cassandra.db.filter.QueryFilter; import org.apache.cassandra.net.*; import org.apache.cassandra.tracing.Tracing; import org.apache.cassandra.utils.CloseableIterator; import org.apache.cassandra.utils.FBUtilities; public class RowDataResolver extends AbstractRowResolver { private int maxLiveCount = 0; public List<AsyncOneResponse> repairResults = Collections.emptyList(); private final IDiskAtomFilter filter; private final long timestamp; public RowDataResolver(String keyspaceName, ByteBuffer key, IDiskAtomFilter qFilter, long timestamp, int maxResponseCount) { super(key, keyspaceName, maxResponseCount); this.filter = qFilter; this.timestamp = timestamp; } /* * This method handles the following scenario: * * there was a mismatch on the initial read, so we redid the digest requests * as full data reads. In this case we need to compute the most recent version * of each column, and send diffs to out-of-date replicas. */ public Row resolve() throws DigestMismatchException { int replyCount = replies.size(); if (logger.isTraceEnabled()) logger.trace("resolving {} responses", replyCount); long start = System.nanoTime(); ColumnFamily resolved; if (replyCount > 1) { List<ColumnFamily> versions = new ArrayList<>(replyCount); List<InetAddress> endpoints = new ArrayList<>(replyCount); for (MessageIn<ReadResponse> message : replies) { ReadResponse response = message.payload; ColumnFamily cf = response.row().cf; assert !response.isDigestQuery() : "Received digest response to repair read from " + message.from; versions.add(cf); endpoints.add(message.from); // compute maxLiveCount to prevent short reads -- see https://issues.apache.org/jira/browse/CASSANDRA-2643 int liveCount = cf == null ? 0 : filter.getLiveCount(cf, timestamp); if (liveCount > maxLiveCount) maxLiveCount = liveCount; } resolved = resolveSuperset(versions, timestamp); if (logger.isTraceEnabled()) logger.trace("versions merged"); // send updates to any replica that was missing part of the full row // (resolved can be null even if versions doesn't have all nulls because of the call to removeDeleted in resolveSuperSet) if (resolved != null) repairResults = scheduleRepairs(resolved, keyspaceName, key, versions, endpoints); } else { resolved = replies.get(0).payload.row().cf; } if (logger.isTraceEnabled()) logger.trace("resolve: {} ms.", TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start)); return new Row(key, resolved); } /** * For each row version, compare with resolved (the superset of all row versions); * if it is missing anything, send a mutation to the endpoint it come from. */ public static List<AsyncOneResponse> scheduleRepairs(ColumnFamily resolved, String keyspaceName, DecoratedKey key, List<ColumnFamily> versions, List<InetAddress> endpoints) { List<AsyncOneResponse> results = new ArrayList<AsyncOneResponse>(versions.size()); for (int i = 0; i < versions.size(); i++) { ColumnFamily diffCf = ColumnFamily.diff(versions.get(i), resolved); if (diffCf == null) // no repair needs to happen continue; // create and send the mutation message based on the diff Mutation mutation = new Mutation(keyspaceName, key.getKey(), diffCf); // use a separate verb here because we don't want these to be get the white glove hint- // on-timeout behavior that a "real" mutation gets Tracing.trace("Sending read-repair-mutation to {}", endpoints.get(i)); results.add(MessagingService.instance() .sendRR(mutation.createMessage(MessagingService.Verb.READ_REPAIR), endpoints.get(i))); } return results; } static ColumnFamily resolveSuperset(Iterable<ColumnFamily> versions, long now) { assert Iterables.size(versions) > 0; ColumnFamily resolved = null; for (ColumnFamily cf : versions) { if (cf == null) continue; if (resolved == null) resolved = cf.cloneMeShallow(); else resolved.delete(cf); } if (resolved == null) return null; // mimic the collectCollatedColumn + removeDeleted path that getColumnFamily takes. // this will handle removing columns and subcolumns that are suppressed by a row or // supercolumn tombstone. QueryFilter filter = new QueryFilter(null, resolved.metadata().cfName, new IdentityQueryFilter(), now); List<CloseableIterator<Cell>> iters = new ArrayList<>(Iterables.size(versions)); for (ColumnFamily version : versions) if (version != null) iters.add(FBUtilities.closeableIterator(version.iterator())); filter.collateColumns(resolved, iters, Integer.MIN_VALUE); return ColumnFamilyStore.removeDeleted(resolved, Integer.MIN_VALUE); } public Row getData() { assert !replies.isEmpty(); return replies.get(0).payload.row(); } public boolean isDataPresent() { return !replies.isEmpty(); } public int getMaxLiveCount() { return maxLiveCount; } }