-
Notifications
You must be signed in to change notification settings - Fork 2.3k
/
LogTailScanner.java
339 lines (308 loc) · 14.5 KB
/
LogTailScanner.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
/*
* Copyright (c) 2002-2017 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.kernel.recovery;
import java.io.IOException;
import org.neo4j.helpers.Exceptions;
import org.neo4j.io.fs.FileSystemAbstraction;
import org.neo4j.kernel.impl.store.UnderlyingStorageException;
import org.neo4j.kernel.impl.transaction.log.LogEntryCursor;
import org.neo4j.kernel.impl.transaction.log.LogPosition;
import org.neo4j.kernel.impl.transaction.log.LogVersionedStoreChannel;
import org.neo4j.kernel.impl.transaction.log.PhysicalLogFile;
import org.neo4j.kernel.impl.transaction.log.PhysicalLogFiles;
import org.neo4j.kernel.impl.transaction.log.ReadAheadLogChannel;
import org.neo4j.kernel.impl.transaction.log.ReadableClosablePositionAwareChannel;
import org.neo4j.kernel.impl.transaction.log.ReadableLogChannel;
import org.neo4j.kernel.impl.transaction.log.entry.CheckPoint;
import org.neo4j.kernel.impl.transaction.log.entry.LogEntry;
import org.neo4j.kernel.impl.transaction.log.entry.LogEntryCommit;
import org.neo4j.kernel.impl.transaction.log.entry.LogEntryReader;
import org.neo4j.kernel.impl.transaction.log.entry.LogEntryStart;
import org.neo4j.kernel.impl.transaction.log.entry.LogEntryVersion;
import org.neo4j.kernel.impl.transaction.log.entry.UnsupportedLogVersionException;
import org.neo4j.kernel.monitoring.Monitors;
import org.neo4j.unsafe.impl.internal.dragons.FeatureToggles;
import static java.lang.String.format;
import static org.neo4j.kernel.impl.transaction.log.LogVersionRepository.INITIAL_LOG_VERSION;
/**
* This class collects information about the latest entries in the transaction log. Since the only way we have to collect
* said information is to scan the transaction log from beginning to end, which is costly, we do this once and save the
* result for others to consume.
* <p>
* Due to the nature of transaction logs and log rotation, a single transaction log file has to be scanned forward, and
* if the required data is not found we search backwards through log file versions.
*/
public class LogTailScanner
{
static long NO_TRANSACTION_ID = -1;
private final PhysicalLogFiles logFiles;
private final FileSystemAbstraction fileSystem;
private final LogEntryReader<ReadableClosablePositionAwareChannel> logEntryReader;
private LogTailInformation logTailInformation;
private final LogTailScannerMonitor monitor;
public LogTailScanner( PhysicalLogFiles logFiles, FileSystemAbstraction fileSystem,
LogEntryReader<ReadableClosablePositionAwareChannel> logEntryReader, Monitors monitors )
{
this.logFiles = logFiles;
this.fileSystem = fileSystem;
this.logEntryReader = logEntryReader;
this.monitor = monitors.newMonitor( LogTailScannerMonitor.class );
}
private LogTailInformation findLogTail() throws IOException
{
final long highestLogVersion = logFiles.getHighestLogVersion();
long version = highestLogVersion;
long versionToSearchForCommits = highestLogVersion;
LogEntryStart latestStartEntry = null;
long oldestStartEntryTransaction = -1;
long oldestVersionFound = -1;
LogEntryVersion latestLogEntryVersion = null;
boolean startRecordAfterCheckpoint = false;
boolean corruptedTransactionLogs = false;
while ( version >= INITIAL_LOG_VERSION )
{
LogVersionedStoreChannel channel =
PhysicalLogFile.tryOpenForVersion( logFiles, fileSystem, version, false );
if ( channel == null )
{
break;
}
oldestVersionFound = version;
CheckPoint latestCheckPoint = null;
ReadableLogChannel recoveredDataChannel = new ReadAheadLogChannel( channel );
try ( LogEntryCursor cursor = new LogEntryCursor( logEntryReader, recoveredDataChannel ) )
{
LogEntry entry;
while ( cursor.next() )
{
entry = cursor.get();
// Collect data about latest checkpoint
if ( entry instanceof CheckPoint )
{
latestCheckPoint = entry.as();
}
else if ( entry instanceof LogEntryCommit )
{
if ( oldestStartEntryTransaction == NO_TRANSACTION_ID )
{
oldestStartEntryTransaction = ((LogEntryCommit) entry).getTxId();
}
}
else if ( entry instanceof LogEntryStart )
{
LogEntryStart startEntry = entry.as();
if ( version == versionToSearchForCommits )
{
latestStartEntry = startEntry;
}
startRecordAfterCheckpoint = true;
}
// Collect data about latest entry version, only in first log file
if ( version == versionToSearchForCommits || latestLogEntryVersion == null )
{
latestLogEntryVersion = entry.getVersion();
}
}
}
catch ( Throwable t )
{
if ( Exceptions.contains( t, UnsupportedLogVersionException.class ) )
{
if ( FeatureToggles.flag( LogTailScanner.class, "force", false ) )
{
monitor.forced( t );
}
else
{
throw new RuntimeException( format( "Unsupported transaction log version found. " +
"To force transactional processing anyway and trip non recognised transactions please " +
"use %s. By using this flag you can lose part of your transactions log. This operation is irretrievable." +
" ", FeatureToggles.toggle( LogTailScanner.class, "force", true ) ), t );
}
}
corruptedTransactionLogs = true;
monitor.corruptedLogFile( version, t );
}
if ( latestCheckPoint != null )
{
return checkpointTailInformation( highestLogVersion, latestStartEntry, oldestVersionFound,
latestLogEntryVersion, latestCheckPoint, corruptedTransactionLogs );
}
version--;
// if we have found no commits in the latest log, keep searching in the next one
if ( latestStartEntry == null )
{
versionToSearchForCommits--;
}
}
return new LogTailInformation( corruptedTransactionLogs || startRecordAfterCheckpoint,
oldestStartEntryTransaction, oldestVersionFound, highestLogVersion, latestLogEntryVersion );
}
protected LogTailInformation checkpointTailInformation( long highestLogVersion, LogEntryStart latestStartEntry,
long oldestVersionFound, LogEntryVersion latestLogEntryVersion, CheckPoint latestCheckPoint,
boolean corruptedTransactionLogs ) throws IOException
{
LogPosition checkPointLogPosition = latestCheckPoint.getLogPosition();
ExtractedTransactionRecord transactionRecord = extractFirstTxIdAfterPosition( checkPointLogPosition, highestLogVersion );
long firstTxIdAfterPosition = transactionRecord.getId();
boolean startRecordAfterCheckpoint = (firstTxIdAfterPosition != NO_TRANSACTION_ID) ||
((latestStartEntry != null) &&
(latestStartEntry.getStartPosition().compareTo( latestCheckPoint.getLogPosition() ) >= 0));
boolean corruptedLogs = transactionRecord.isFailure() || corruptedTransactionLogs;
return new LogTailInformation( latestCheckPoint, corruptedLogs || startRecordAfterCheckpoint,
firstTxIdAfterPosition, oldestVersionFound, highestLogVersion, latestLogEntryVersion );
}
/**
* Extracts txId from first commit entry, when starting reading at the given {@code position}.
* If no commit entry found in the version, the reader will continue into next version(s) up till
* {@code maxLogVersion} until finding one.
*
* @param initialPosition {@link LogPosition} to start scan from.
* @param maxLogVersion max log version to scan.
* @return value object that contains first transaction id of closes commit entry to {@code initialPosition},
* or {@link LogTailInformation#NO_TRANSACTION_ID} if not found. And failure flag that will be set to true if
* there was some exception during transaction log processing.
* @throws IOException on channel close I/O error.
*/
protected ExtractedTransactionRecord extractFirstTxIdAfterPosition( LogPosition initialPosition, long maxLogVersion ) throws IOException
{
LogPosition currentPosition = initialPosition;
ExtractedTransactionRecord transactionRecord = new ExtractedTransactionRecord();
while ( currentPosition.getLogVersion() <= maxLogVersion )
{
LogVersionedStoreChannel storeChannel = PhysicalLogFile.tryOpenForVersion( logFiles, fileSystem,
currentPosition.getLogVersion(), false );
if ( storeChannel != null )
{
try
{
storeChannel.position( currentPosition.getByteOffset() );
try ( ReadAheadLogChannel logChannel = new ReadAheadLogChannel( storeChannel );
LogEntryCursor cursor = new LogEntryCursor( logEntryReader, logChannel ) )
{
while ( cursor.next() )
{
LogEntry entry = cursor.get();
if ( entry instanceof LogEntryCommit )
{
transactionRecord.setId( ((LogEntryCommit) entry).getTxId() );
return transactionRecord;
}
}
}
}
catch ( Throwable t )
{
monitor.corruptedLogFile( currentPosition.getLogVersion(), t );
transactionRecord.setFailure( true );
return transactionRecord;
}
finally
{
storeChannel.close();
}
}
currentPosition = LogPosition.start( currentPosition.getLogVersion() + 1 );
}
return transactionRecord;
}
/**
* Collects information about the tail of the transaction log, i.e. last checkpoint, last entry etc.
* Since this is an expensive task we do it once and reuse the result. This method is thus lazy and the first one
* calling it will take the hit.
* <p>
* This is only intended to be used during startup. If you need to track the state of the tail, that can be done more
* efficiently at runtime, and this method should then only be used to restore said state.
*
* @return snapshot of the state of the transaction logs tail at startup.
* @throws UnderlyingStorageException if any errors occurs while parsing the transaction logs
*/
public LogTailInformation getTailInformation() throws UnderlyingStorageException
{
if ( logTailInformation == null )
{
try
{
logTailInformation = findLogTail();
}
catch ( IOException e )
{
throw new UnderlyingStorageException( "Error encountered while parsing transaction logs", e );
}
}
return logTailInformation;
}
static class ExtractedTransactionRecord
{
private long id;
private boolean failure;
ExtractedTransactionRecord()
{
id = NO_TRANSACTION_ID;
failure = false;
}
public long getId()
{
return id;
}
public void setId( long id )
{
this.id = id;
}
public boolean isFailure()
{
return failure;
}
public void setFailure( boolean failure )
{
this.failure = failure;
}
}
public static class LogTailInformation
{
public final CheckPoint lastCheckPoint;
public final long firstTxIdAfterLastCheckPoint;
public final long oldestLogVersionFound;
public final long currentLogVersion;
public final LogEntryVersion latestLogEntryVersion;
private final boolean recordAfterCheckpoint;
public LogTailInformation( boolean recordAfterCheckpoint, long firstTxIdAfterLastCheckPoint,
long oldestLogVersionFound, long currentLogVersion,
LogEntryVersion latestLogEntryVersion )
{
this( null, recordAfterCheckpoint, firstTxIdAfterLastCheckPoint, oldestLogVersionFound, currentLogVersion,
latestLogEntryVersion );
}
LogTailInformation( CheckPoint lastCheckPoint, boolean recordAfterCheckpoint, long firstTxIdAfterLastCheckPoint,
long oldestLogVersionFound, long currentLogVersion, LogEntryVersion latestLogEntryVersion )
{
this.lastCheckPoint = lastCheckPoint;
this.firstTxIdAfterLastCheckPoint = firstTxIdAfterLastCheckPoint;
this.oldestLogVersionFound = oldestLogVersionFound;
this.currentLogVersion = currentLogVersion;
this.latestLogEntryVersion = latestLogEntryVersion;
this.recordAfterCheckpoint = recordAfterCheckpoint;
}
public boolean commitsAfterLastCheckpoint()
{
return recordAfterCheckpoint;
}
}
}