Java tutorial
/* * Copyright 2015-2016 Cask Data, Inc. * * Licensed 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 co.cask.tephra.hbase10.coprocessor; import co.cask.tephra.Transaction; import co.cask.tephra.TransactionCodec; import co.cask.tephra.TxConstants; import co.cask.tephra.coprocessor.TransactionStateCache; import co.cask.tephra.coprocessor.TransactionStateCacheSupplier; import co.cask.tephra.persist.TransactionVisibilityState; import co.cask.tephra.util.TxUtils; import com.google.common.base.Supplier; import com.google.common.collect.Maps; import com.google.common.collect.Sets; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.hbase.Cell; import org.apache.hadoop.hbase.CellUtil; import org.apache.hadoop.hbase.CoprocessorEnvironment; import org.apache.hadoop.hbase.HColumnDescriptor; import org.apache.hadoop.hbase.HConstants; import org.apache.hadoop.hbase.HTableDescriptor; import org.apache.hadoop.hbase.client.Delete; import org.apache.hadoop.hbase.client.Durability; import org.apache.hadoop.hbase.client.Get; import org.apache.hadoop.hbase.client.OperationWithAttributes; import org.apache.hadoop.hbase.client.Put; import org.apache.hadoop.hbase.client.Scan; import org.apache.hadoop.hbase.coprocessor.BaseRegionObserver; import org.apache.hadoop.hbase.coprocessor.ObserverContext; import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment; import org.apache.hadoop.hbase.filter.Filter; import org.apache.hadoop.hbase.filter.FilterBase; import org.apache.hadoop.hbase.regionserver.InternalScanner; import org.apache.hadoop.hbase.regionserver.KeyValueScanner; import org.apache.hadoop.hbase.regionserver.RegionScanner; import org.apache.hadoop.hbase.regionserver.ScanType; import org.apache.hadoop.hbase.regionserver.Store; import org.apache.hadoop.hbase.regionserver.StoreScanner; import org.apache.hadoop.hbase.regionserver.compactions.CompactionRequest; import org.apache.hadoop.hbase.regionserver.wal.WALEdit; import org.apache.hadoop.hbase.util.Bytes; import java.io.IOException; import java.util.Collection; import java.util.Collections; import java.util.List; import java.util.Map; import java.util.NavigableSet; import java.util.Set; /** * {@code org.apache.hadoop.hbase.coprocessor.RegionObserver} coprocessor that handles server-side processing * for transactions: * <ul> * <li>applies filtering to exclude data from invalid and in-progress transactions</li> * <li>overrides the scanner returned for flush and compaction to drop data written by invalidated transactions, * or expired due to TTL.</li> * </ul> * * <p>In order to use this coprocessor for transactions, configure the class on any table involved in transactions, * or on all user tables by adding the following to hbase-site.xml: * {@code * <property> * <name>hbase.coprocessor.region.classes</name> * <value>co.cask.tephra.hbase10.coprocessor.TransactionProcessor</value> * </property> * } * </p> * * <p>HBase {@code Get} and {@code Scan} operations should have the current transaction serialized on to the operation * as an attribute: * {@code * Transaction t = ...; * Get get = new Get(...); * TransactionCodec codec = new TransactionCodec(); * codec.addToOperation(get, t); * } * </p> */ public class TransactionProcessor extends BaseRegionObserver { private static final Log LOG = LogFactory.getLog(TransactionProcessor.class); private TransactionStateCache cache; private final TransactionCodec txCodec; protected Map<byte[], Long> ttlByFamily = Maps.newTreeMap(Bytes.BYTES_COMPARATOR); protected boolean allowEmptyValues = TxConstants.ALLOW_EMPTY_VALUES_DEFAULT; protected boolean readNonTxnData = TxConstants.DEFAULT_READ_NON_TX_DATA; public TransactionProcessor() { this.txCodec = new TransactionCodec(); } /* RegionObserver implementation */ @Override public void start(CoprocessorEnvironment e) throws IOException { if (e instanceof RegionCoprocessorEnvironment) { RegionCoprocessorEnvironment env = (RegionCoprocessorEnvironment) e; Supplier<TransactionStateCache> cacheSupplier = getTransactionStateCacheSupplier(env); this.cache = cacheSupplier.get(); HTableDescriptor tableDesc = env.getRegion().getTableDesc(); for (HColumnDescriptor columnDesc : tableDesc.getFamilies()) { String columnTTL = columnDesc.getValue(TxConstants.PROPERTY_TTL); long ttl = 0; if (columnTTL != null) { try { ttl = Long.parseLong(columnTTL); LOG.info("Family " + columnDesc.getNameAsString() + " has TTL of " + columnTTL); } catch (NumberFormatException nfe) { LOG.warn("Invalid TTL value configured for column family " + columnDesc.getNameAsString() + ", value = " + columnTTL); } } ttlByFamily.put(columnDesc.getName(), ttl); } this.allowEmptyValues = env.getConfiguration().getBoolean(TxConstants.ALLOW_EMPTY_VALUES_KEY, TxConstants.ALLOW_EMPTY_VALUES_DEFAULT); this.readNonTxnData = Boolean.valueOf(tableDesc.getValue(TxConstants.READ_NON_TX_DATA)); if (readNonTxnData) { LOG.info("Reading pre-existing data enabled for table " + tableDesc.getNameAsString()); } } } protected Supplier<TransactionStateCache> getTransactionStateCacheSupplier(RegionCoprocessorEnvironment env) { return new TransactionStateCacheSupplier(env.getConfiguration()); } @Override public void stop(CoprocessorEnvironment e) throws IOException { // nothing to do } @Override public void preGetOp(ObserverContext<RegionCoprocessorEnvironment> e, Get get, List<Cell> results) throws IOException { Transaction tx = getFromOperation(get); if (tx != null) { projectFamilyDeletes(get); get.setMaxVersions(); get.setTimeRange(TxUtils.getOldestVisibleTimestamp(ttlByFamily, tx, readNonTxnData), TxUtils.getMaxVisibleTimestamp(tx)); Filter newFilter = getTransactionFilter(tx, ScanType.USER_SCAN, get.getFilter()); get.setFilter(newFilter); } } @Override public void preDelete(ObserverContext<RegionCoprocessorEnvironment> e, Delete delete, WALEdit edit, Durability durability) throws IOException { // Translate deletes into our own delete tombstones // Since HBase deletes cannot be undone, we need to translate deletes into special puts, which allows // us to rollback the changes (by a real delete) if the transaction fails // Deletes that are part of a transaction rollback do not need special handling. // They will never be rolled back, so are performed as normal HBase deletes. if (delete.getAttribute(TxConstants.TX_ROLLBACK_ATTRIBUTE_KEY) != null) { return; } // Other deletes are client-initiated and need to be translated into our own tombstones // TODO: this should delegate to the DeleteStrategy implementation. Put deleteMarkers = new Put(delete.getRow(), delete.getTimeStamp()); for (byte[] family : delete.getFamilyCellMap().keySet()) { List<Cell> familyCells = delete.getFamilyCellMap().get(family); if (isFamilyDelete(familyCells)) { deleteMarkers.add(family, TxConstants.FAMILY_DELETE_QUALIFIER, familyCells.get(0).getTimestamp(), HConstants.EMPTY_BYTE_ARRAY); } else { int cellSize = familyCells.size(); for (int i = 0; i < cellSize; i++) { Cell cell = familyCells.get(i); deleteMarkers.add(family, CellUtil.cloneQualifier(cell), cell.getTimestamp(), HConstants.EMPTY_BYTE_ARRAY); } } } for (Map.Entry<String, byte[]> entry : delete.getAttributesMap().entrySet()) { deleteMarkers.setAttribute(entry.getKey(), entry.getValue()); } e.getEnvironment().getRegion().put(deleteMarkers); // skip normal delete handling e.bypass(); } private boolean isFamilyDelete(List<Cell> familyCells) { return familyCells.size() == 1 && CellUtil.isDeleteFamily(familyCells.get(0)); } @Override public RegionScanner preScannerOpen(ObserverContext<RegionCoprocessorEnvironment> e, Scan scan, RegionScanner s) throws IOException { Transaction tx = getFromOperation(scan); if (tx != null) { projectFamilyDeletes(scan); scan.setMaxVersions(); scan.setTimeRange(TxUtils.getOldestVisibleTimestamp(ttlByFamily, tx, readNonTxnData), TxUtils.getMaxVisibleTimestamp(tx)); Filter newFilter = getTransactionFilter(tx, ScanType.USER_SCAN, scan.getFilter()); scan.setFilter(newFilter); } return s; } /** * Ensures that family delete markers are present in the columns requested for any scan operation. * @param scan The original scan request * @return The modified scan request with the family delete qualifiers represented */ private Scan projectFamilyDeletes(Scan scan) { for (Map.Entry<byte[], NavigableSet<byte[]>> entry : scan.getFamilyMap().entrySet()) { NavigableSet<byte[]> columns = entry.getValue(); // wildcard scans will automatically include the delete marker, so only need to add it when we have // explicit columns listed if (columns != null && !columns.isEmpty()) { scan.addColumn(entry.getKey(), TxConstants.FAMILY_DELETE_QUALIFIER); } } return scan; } /** * Ensures that family delete markers are present in the columns requested for any get operation. * @param get The original get request * @return The modified get request with the family delete qualifiers represented */ private Get projectFamilyDeletes(Get get) { for (Map.Entry<byte[], NavigableSet<byte[]>> entry : get.getFamilyMap().entrySet()) { NavigableSet<byte[]> columns = entry.getValue(); // wildcard scans will automatically include the delete marker, so only need to add it when we have // explicit columns listed if (columns != null && !columns.isEmpty()) { get.addColumn(entry.getKey(), TxConstants.FAMILY_DELETE_QUALIFIER); } } return get; } @Override public InternalScanner preFlushScannerOpen(ObserverContext<RegionCoprocessorEnvironment> c, Store store, KeyValueScanner memstoreScanner, InternalScanner scanner) throws IOException { return createStoreScanner(c.getEnvironment(), "flush", cache.getLatestState(), store, Collections.singletonList(memstoreScanner), ScanType.COMPACT_RETAIN_DELETES, HConstants.OLDEST_TIMESTAMP); } @Override public InternalScanner preCompactScannerOpen(ObserverContext<RegionCoprocessorEnvironment> c, Store store, List<? extends KeyValueScanner> scanners, ScanType scanType, long earliestPutTs, InternalScanner s, CompactionRequest request) throws IOException { return createStoreScanner(c.getEnvironment(), "compaction", cache.getLatestState(), store, scanners, scanType, earliestPutTs); } protected InternalScanner createStoreScanner(RegionCoprocessorEnvironment env, String action, TransactionVisibilityState snapshot, Store store, List<? extends KeyValueScanner> scanners, ScanType type, long earliestPutTs) throws IOException { if (snapshot == null) { if (LOG.isDebugEnabled()) { LOG.debug("Region " + env.getRegion().getRegionNameAsString() + ", no current transaction state found, defaulting to normal " + action + " scanner"); } return null; } // construct a dummy transaction from the latest snapshot Transaction dummyTx = TxUtils.createDummyTransaction(snapshot); Scan scan = new Scan(); // need to see all versions, since we filter out excludes and applications may rely on multiple versions scan.setMaxVersions(); scan.setFilter(new IncludeInProgressFilter(dummyTx.getVisibilityUpperBound(), snapshot.getInvalid(), getTransactionFilter(dummyTx, type, null))); return new StoreScanner(store, store.getScanInfo(), scan, scanners, type, store.getSmallestReadPoint(), earliestPutTs); } private Transaction getFromOperation(OperationWithAttributes op) throws IOException { byte[] encoded = op.getAttribute(TxConstants.TX_OPERATION_ATTRIBUTE_KEY); if (encoded != null) { return txCodec.decode(encoded); } return null; } /** * Derived classes can override this method to customize the filter used to return data visible for the current * transaction. * * @param tx the current transaction to apply * @param type the type of scan being performed */ protected Filter getTransactionFilter(Transaction tx, ScanType type, Filter filter) { return TransactionFilters.getVisibilityFilter(tx, ttlByFamily, allowEmptyValues, type, filter); } /** * Filter used to include cells visible to in-progress transactions on flush and commit. */ static class IncludeInProgressFilter extends FilterBase { private final long visibilityUpperBound; private final Set<Long> invalidIds; private final Filter txFilter; public IncludeInProgressFilter(long upperBound, Collection<Long> invalids, Filter transactionFilter) { this.visibilityUpperBound = upperBound; this.invalidIds = Sets.newHashSet(invalids); this.txFilter = transactionFilter; } @Override public ReturnCode filterKeyValue(Cell cell) throws IOException { // include all cells visible to in-progress transactions, except for those already marked as invalid long ts = cell.getTimestamp(); if (ts > visibilityUpperBound) { // include everything that could still be in-progress except invalids if (invalidIds.contains(ts)) { return ReturnCode.SKIP; } return ReturnCode.INCLUDE; } return txFilter.filterKeyValue(cell); } } }