| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.store.raw.log.FlushedScan |
| 4 | |
| 5 | Copyright 1997, 2004 The Apache Software Foundation or its licensors, as applicable. |
| 6 | |
| 7 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 8 | you may not use this file except in compliance with the License. |
| 9 | You may obtain a copy of the License at |
| 10 | |
| 11 | http://www.apache.org/licenses/LICENSE-2.0 |
| 12 | |
| 13 | Unless required by applicable law or agreed to in writing, software |
| 14 | distributed under the License is distributed on an "AS IS" BASIS, |
| 15 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 16 | See the License for the specific language governing permissions and |
| 17 | limitations under the License. |
| 18 | |
| 19 | */ |
| 20 | |
| 21 | package org.apache.derby.impl.store.raw.log; |
| 22 | |
| 23 | import org.apache.derby.iapi.reference.SQLState; |
| 24 | import org.apache.derby.iapi.reference.MessageId; |
| 25 | |
| 26 | import org.apache.derby.impl.store.raw.log.LogCounter; |
| 27 | import org.apache.derby.impl.store.raw.log.LogRecord; |
| 28 | import org.apache.derby.impl.store.raw.log.StreamLogScan; |
| 29 | |
| 30 | import org.apache.derby.iapi.services.sanity.SanityManager; |
| 31 | import org.apache.derby.iapi.error.StandardException; |
| 32 | import org.apache.derby.iapi.services.i18n.MessageService; |
| 33 | import org.apache.derby.iapi.store.raw.log.LogInstant; |
| 34 | import org.apache.derby.iapi.store.raw.log.LogFactory; |
| 35 | import org.apache.derby.iapi.store.raw.xact.TransactionId; |
| 36 | import org.apache.derby.iapi.services.io.ArrayInputStream; |
| 37 | |
| 38 | import org.apache.derby.io.StorageRandomAccessFile; |
| 39 | |
| 40 | import java.io.IOException; |
| 41 | |
| 42 | /** |
| 43 | |
| 44 | Scan the the log which is implemented by a series of log files.n |
| 45 | This log scan knows how to move across log file if it is positioned at |
| 46 | the boundary of a log file and needs to getNextRecord. |
| 47 | |
| 48 | <PRE> |
| 49 | 4 bytes - length of user data, i.e. N |
| 50 | 8 bytes - long representing log instant |
| 51 | N bytes of supplied data |
| 52 | 4 bytes - length of user data, i.e. N |
| 53 | </PRE> |
| 54 | |
| 55 | */ |
| 56 | public class FlushedScan implements StreamLogScan { |
| 57 | |
| 58 | private StorageRandomAccessFile scan; // an output stream to the log file |
| 59 | LogToFile logFactory; // log factory knows how to to skip |
| 60 | // from log file to log file |
| 61 | |
| 62 | boolean open; // true if the scan is open |
| 63 | |
| 64 | long currentLogFileNumber; // the log file the scan is currently on |
| 65 | |
| 66 | long currentLogFileFirstUnflushedPosition; |
| 67 | // The length of the unflushed portion |
| 68 | // of the current log file. This is the |
| 69 | // length of the file for all but the |
| 70 | // last log file. |
| 71 | |
| 72 | long currentInstant; // the log instant the scan is |
| 73 | // currently on - only valid after a |
| 74 | // successful getNextRecord |
| 75 | |
| 76 | long firstUnflushed = -1; // scan until we reach the first |
| 77 | // unflushed byte in the log. |
| 78 | long firstUnflushedFileNumber; |
| 79 | long firstUnflushedFilePosition; |
| 80 | |
| 81 | //RESOLVE: This belongs in a shared place. |
| 82 | static final int LOG_REC_LEN_BYTE_LENGTH = 4; |
| 83 | |
| 84 | public FlushedScan(LogToFile logFactory, long startAt) |
| 85 | throws StandardException |
| 86 | { |
| 87 | if (SanityManager.DEBUG) |
| 88 | { |
| 89 | SanityManager.ASSERT(startAt != LogCounter.INVALID_LOG_INSTANT, |
| 90 | "cannot start scan on an invalid log instant"); |
| 91 | } |
| 92 | |
| 93 | try |
| 94 | { |
| 95 | currentLogFileNumber = LogCounter.getLogFileNumber(startAt); |
| 96 | this.logFactory = logFactory; |
| 97 | scan = logFactory.getLogFileAtPosition(startAt); |
| 98 | setFirstUnflushed(); |
| 99 | open = true; |
| 100 | currentInstant = LogCounter.INVALID_LOG_INSTANT; // set at getNextRecord |
| 101 | } |
| 102 | |
| 103 | catch (IOException ioe) |
| 104 | { |
| 105 | throw logFactory.markCorrupt( |
| 106 | StandardException.newException(SQLState.LOG_IO_ERROR, ioe)); |
| 107 | } |
| 108 | } |
| 109 | |
| 110 | /* |
| 111 | ** Methods of LogScan |
| 112 | */ |
| 113 | |
| 114 | /** |
| 115 | Read a log record into the byte array provided. Resize the input |
| 116 | stream byte array if necessary. |
| 117 | |
| 118 | @return the length of the data written into data, or -1 if the end of the |
| 119 | scan has been reached. |
| 120 | |
| 121 | @exception StandardException Standard Cloudscape error policy |
| 122 | */ |
| 123 | public LogRecord getNextRecord(ArrayInputStream input, |
| 124 | TransactionId tranId, |
| 125 | int groupmask) |
| 126 | throws StandardException |
| 127 | { |
| 128 | try |
| 129 | { |
| 130 | boolean candidate; |
| 131 | int peekAmount = LogRecord.formatOverhead() + LogRecord.maxGroupStoredSize(); |
| 132 | if (tranId != null) |
| 133 | peekAmount += LogRecord.maxTransactionIdStoredSize(tranId); |
| 134 | int readAmount; // the number of bytes actually read |
| 135 | |
| 136 | LogRecord lr; |
| 137 | |
| 138 | do |
| 139 | { |
| 140 | if (!open || !positionToNextRecord()) |
| 141 | return null; |
| 142 | |
| 143 | int checkLength; |
| 144 | |
| 145 | // this log record is a candidate unless proven otherwise |
| 146 | lr = null; |
| 147 | candidate = true; |
| 148 | readAmount = -1; |
| 149 | |
| 150 | currentInstant = scan.readLong(); |
| 151 | byte[] data = input.getData(); |
| 152 | if (data.length < nextRecordLength) |
| 153 | { |
| 154 | // make a new array of sufficient size and reset the arrary |
| 155 | // in the input stream |
| 156 | data = new byte[nextRecordLength]; |
| 157 | input.setData(data); |
| 158 | } |
| 159 | |
| 160 | if (logFactory.databaseEncrypted()) |
| 161 | { |
| 162 | scan.readFully(data, 0, nextRecordLength); |
| 163 | int len = logFactory.decrypt(data, 0, nextRecordLength, data, 0); |
| 164 | if (SanityManager.DEBUG) |
| 165 | SanityManager.ASSERT(len == nextRecordLength); |
| 166 | input.setLimit(0, len); |
| 167 | |
| 168 | } |
| 169 | else // no need to decrypt, only get the group and tid if we filter |
| 170 | { |
| 171 | if (groupmask == 0 && tranId == null) |
| 172 | { |
| 173 | // no filter, get the whole thing |
| 174 | scan.readFully(data, 0, nextRecordLength); |
| 175 | input.setLimit(0, nextRecordLength); |
| 176 | } |
| 177 | else |
| 178 | { |
| 179 | // Read only enough so that group and the tran id is in |
| 180 | // the data buffer. Group is stored as compressed int |
| 181 | // and tran id is stored as who knows what. read min |
| 182 | // of peekAmount or nextRecordLength |
| 183 | readAmount = (nextRecordLength > peekAmount) ? |
| 184 | peekAmount : nextRecordLength; |
| 185 | |
| 186 | // in the data buffer, we now have enough to peek |
| 187 | scan.readFully(data, 0, readAmount); |
| 188 | input.setLimit(0, readAmount); |
| 189 | |
| 190 | } |
| 191 | } |
| 192 | |
| 193 | lr = (LogRecord) input.readObject(); |
| 194 | |
| 195 | if (groupmask != 0 || tranId != null) |
| 196 | { |
| 197 | if (groupmask != 0 && (groupmask & lr.group()) == 0) |
| 198 | candidate = false; // no match, throw this log record out |
| 199 | |
| 200 | if (candidate && tranId != null) |
| 201 | { |
| 202 | TransactionId tid = lr.getTransactionId(); |
| 203 | if (!tid.equals(tranId)) // nomatch |
| 204 | candidate = false; // throw this log record out |
| 205 | } |
| 206 | |
| 207 | // if this log record is not filtered out, we need to read |
| 208 | // in the rest of the log record to the input buffer. |
| 209 | // Except if it is an encrypted database, in which case the |
| 210 | // entire log record have already be read in for |
| 211 | // decryption. |
| 212 | |
| 213 | if (candidate && !logFactory.databaseEncrypted()) |
| 214 | { |
| 215 | // read the rest of the log into the buffer |
| 216 | if (SanityManager.DEBUG) |
| 217 | SanityManager.ASSERT(readAmount > 0); |
| 218 | |
| 219 | if (readAmount < nextRecordLength) |
| 220 | { |
| 221 | // Need to remember where we are because the log |
| 222 | // record may have read part of it off the input |
| 223 | // stream already and that position is lost when we |
| 224 | // set limit again. |
| 225 | int inputPosition = input.getPosition(); |
| 226 | |
| 227 | scan.readFully(data, readAmount, |
| 228 | nextRecordLength-readAmount); |
| 229 | |
| 230 | input.setLimit(0, nextRecordLength); |
| 231 | input.setPosition(inputPosition); |
| 232 | } |
| 233 | } |
| 234 | } |
| 235 | |
| 236 | if (candidate || logFactory.databaseEncrypted()) |
| 237 | { |
| 238 | checkLength = scan.readInt(); |
| 239 | |
| 240 | if (SanityManager.DEBUG) |
| 241 | { |
| 242 | SanityManager.ASSERT(checkLength == nextRecordLength, "log currupted"); |
| 243 | } |
| 244 | } |
| 245 | else // chances are, we haven't read all of the log record, skip it |
| 246 | { |
| 247 | // the starting record position is in the currentInstant, |
| 248 | // calculate the next record starting position using that |
| 249 | // and the nextRecordLength |
| 250 | long nextRecordStartPosition = |
| 251 | LogCounter.getLogFilePosition(currentInstant) + |
| 252 | nextRecordLength + LogToFile.LOG_RECORD_OVERHEAD; |
| 253 | |
| 254 | scan.seek(nextRecordStartPosition); |
| 255 | } |
| 256 | |
| 257 | } while (candidate == false); |
| 258 | |
| 259 | return lr; |
| 260 | } |
| 261 | catch (ClassNotFoundException cnfe) |
| 262 | { |
| 263 | throw logFactory.markCorrupt( |
| 264 | StandardException.newException(SQLState.LOG_CORRUPTED, cnfe)); |
| 265 | } |
| 266 | catch (IOException ioe) |
| 267 | { |
| 268 | throw logFactory.markCorrupt( |
| 269 | StandardException.newException(SQLState.LOG_IO_ERROR, ioe)); |
| 270 | } |
| 271 | } |
| 272 | |
| 273 | /** |
| 274 | Reset the scan to the given LogInstant. |
| 275 | |
| 276 | @param instant the position to reset to |
| 277 | @exception IOException scan cannot access the log at the new position. |
| 278 | */ |
| 279 | public void resetPosition(LogInstant instant) throws IOException |
| 280 | { |
| 281 | if (SanityManager.DEBUG) |
| 282 | { |
| 283 | SanityManager.THROWASSERT("Unsupported feature"); |
| 284 | } |
| 285 | } |
| 286 | |
| 287 | /** |
| 288 | Get the log instant that is right after the record just retrived |
| 289 | @return INVALID_LOG_INSTANT if this is not a FORWARD scan or, no |
| 290 | record have been returned yet or the scan has completed. |
| 291 | */ |
| 292 | public long getLogRecordEnd() |
| 293 | { |
| 294 | if (SanityManager.DEBUG) |
| 295 | { |
| 296 | SanityManager.THROWASSERT("Unsupported feature"); |
| 297 | } |
| 298 | return LogCounter.INVALID_LOG_INSTANT; |
| 299 | } |
| 300 | |
| 301 | |
| 302 | /** |
| 303 | returns true if there is partially writen log records before the crash |
| 304 | in the last log file. Partiall wrires are identified during forward |
| 305 | scans for log recovery. |
| 306 | */ |
| 307 | public boolean isLogEndFuzzy() |
| 308 | { |
| 309 | if (SanityManager.DEBUG) |
| 310 | { |
| 311 | SanityManager.THROWASSERT("Unsupported feature"); |
| 312 | } |
| 313 | return false; |
| 314 | } |
| 315 | |
| 316 | /** |
| 317 | Return the log instant (as an integer) the scan is currently on - this is the log |
| 318 | instant of the log record that was returned by getNextRecord. |
| 319 | */ |
| 320 | public long getInstant() |
| 321 | { |
| 322 | return currentInstant; |
| 323 | } |
| 324 | |
| 325 | /** |
| 326 | Return the log instant the scan is currently on - this is the log |
| 327 | instant of the log record that was returned by getNextRecord. |
| 328 | */ |
| 329 | public LogInstant getLogInstant() |
| 330 | { |
| 331 | if (currentInstant == LogCounter.INVALID_LOG_INSTANT) |
| 332 | return null; |
| 333 | else |
| 334 | return new LogCounter(currentInstant); |
| 335 | } |
| 336 | |
| 337 | /** |
| 338 | Close the scan. |
| 339 | */ |
| 340 | public void close() |
| 341 | { |
| 342 | if (scan != null) |
| 343 | { |
| 344 | try |
| 345 | { |
| 346 | scan.close(); |
| 347 | } |
| 348 | catch (IOException ioe) |
| 349 | {} |
| 350 | |
| 351 | scan = null; |
| 352 | } |
| 353 | currentInstant = LogCounter.INVALID_LOG_INSTANT; |
| 354 | open = false; |
| 355 | } |
| 356 | |
| 357 | /* |
| 358 | Private methods. |
| 359 | */ |
| 360 | private void setFirstUnflushed() |
| 361 | throws StandardException, IOException |
| 362 | { |
| 363 | LogInstant firstUnflushedInstant = |
| 364 | logFactory.getFirstUnflushedInstant(); |
| 365 | firstUnflushed = ((LogCounter)firstUnflushedInstant).getValueAsLong(); |
| 366 | firstUnflushedFileNumber = LogCounter.getLogFileNumber(firstUnflushed); |
| 367 | firstUnflushedFilePosition = LogCounter.getLogFilePosition(firstUnflushed); |
| 368 | |
| 369 | setCurrentLogFileFirstUnflushedPosition(); |
| 370 | } |
| 371 | |
| 372 | private void setCurrentLogFileFirstUnflushedPosition() |
| 373 | throws IOException |
| 374 | { |
| 375 | /* |
| 376 | Note we get the currentLogFileLength without synchronization. |
| 377 | This is safe because one of the following cases apply: |
| 378 | |
| 379 | <OL> |
| 380 | <LI> The end of the flushed section of the log is in another file. |
| 381 | In this case the end of the current file will not change. |
| 382 | <LI> The end of the log is in this file. In this case we |
| 383 | end our scan at the firstUnflushedInstant and do not use |
| 384 | currentLogFileLength. |
| 385 | </OL> |
| 386 | */ |
| 387 | if (currentLogFileNumber == firstUnflushedFileNumber) |
| 388 | currentLogFileFirstUnflushedPosition = firstUnflushedFilePosition; |
| 389 | else if (currentLogFileNumber < firstUnflushedFileNumber) |
| 390 | currentLogFileFirstUnflushedPosition = scan.length(); |
| 391 | else |
| 392 | { |
| 393 | // RESOLVE |
| 394 | throw new IOException( |
| 395 | MessageService.getTextMessage(MessageId.LOG_BAD_START_INSTANT)); |
| 396 | } |
| 397 | } |
| 398 | |
| 399 | private void switchLogFile() |
| 400 | throws StandardException |
| 401 | { |
| 402 | try |
| 403 | { |
| 404 | readNextRecordLength = false; |
| 405 | scan.close(); |
| 406 | scan = null; |
| 407 | scan = logFactory.getLogFileAtBeginning(++currentLogFileNumber); |
| 408 | setCurrentLogFileFirstUnflushedPosition(); |
| 409 | } |
| 410 | |
| 411 | catch (IOException ioe) |
| 412 | { |
| 413 | throw logFactory.markCorrupt( |
| 414 | StandardException.newException(SQLState.LOG_IO_ERROR, ioe)); |
| 415 | } |
| 416 | } |
| 417 | |
| 418 | /** |
| 419 | The length of the next record. Read from scan and set by |
| 420 | currentLogFileHasUnflushedRecord. This is used to retain the length of a |
| 421 | log record in the case currentLogFileHasUnflushedRecord reads the length |
| 422 | and determines that some bytes in the log record are not yet flushed. |
| 423 | */ |
| 424 | int nextRecordLength; |
| 425 | |
| 426 | /** |
| 427 | Flag to indicate that the length of the next log record has been read by |
| 428 | currentLogFileHasUnflushedRecord. |
| 429 | |
| 430 | This flag gets reset in two ways: |
| 431 | |
| 432 | <OL> |
| 433 | <LI> currentLogFileHasUnflushedRecord determines that the entire log |
| 434 | record is flushed and returns true. In this case getNextRecord reads and |
| 435 | returns the log record. |
| 436 | <LI> we switch log files --due to a partial log record at the end of an |
| 437 | old log file. |
| 438 | </OL> |
| 439 | */ |
| 440 | boolean readNextRecordLength; |
| 441 | |
| 442 | private boolean currentLogFileHasUnflushedRecord() |
| 443 | throws IOException |
| 444 | { |
| 445 | if (SanityManager.DEBUG) |
| 446 | SanityManager.ASSERT(scan != null, "scan is null"); |
| 447 | long curPos = scan.getFilePointer(); |
| 448 | |
| 449 | if (!readNextRecordLength) |
| 450 | { |
| 451 | if (curPos + LOG_REC_LEN_BYTE_LENGTH > |
| 452 | currentLogFileFirstUnflushedPosition) |
| 453 | return false; |
| 454 | |
| 455 | nextRecordLength = scan.readInt(); |
| 456 | curPos+=4; |
| 457 | readNextRecordLength = true; |
| 458 | } |
| 459 | |
| 460 | if (nextRecordLength==0) return false; |
| 461 | |
| 462 | int bytesNeeded = |
| 463 | nextRecordLength + LOG_REC_LEN_BYTE_LENGTH; |
| 464 | |
| 465 | if (curPos + bytesNeeded > currentLogFileFirstUnflushedPosition) |
| 466 | { |
| 467 | return false; |
| 468 | } |
| 469 | else |
| 470 | { |
| 471 | readNextRecordLength = false; |
| 472 | return true; |
| 473 | } |
| 474 | } |
| 475 | |
| 476 | private boolean positionToNextRecord() |
| 477 | throws StandardException, IOException |
| 478 | { |
| 479 | //If the flushed section of the current log file contains our record we |
| 480 | //simply return. |
| 481 | if (currentLogFileHasUnflushedRecord()) return true; |
| 482 | |
| 483 | //Update our cached copy of the first unflushed instant. |
| 484 | setFirstUnflushed(); |
| 485 | |
| 486 | //In the call to setFirstUnflushed, we may have noticed that the current |
| 487 | //log file really does contain our record. If so we simply return. |
| 488 | if (currentLogFileHasUnflushedRecord()) return true; |
| 489 | |
| 490 | //Our final chance of finding a record is if we are not scanning the log |
| 491 | //file with the last flushed instant we can switch logfiles. Note that |
| 492 | //we do this in a loop to cope with empty log files. |
| 493 | while(currentLogFileNumber < firstUnflushedFileNumber) |
| 494 | { |
| 495 | switchLogFile(); |
| 496 | if (currentLogFileHasUnflushedRecord()) return true; |
| 497 | } |
| 498 | |
| 499 | //The log contains no more flushed log records so we return false. |
| 500 | currentInstant = LogCounter.INVALID_LOG_INSTANT; |
| 501 | return false; |
| 502 | } |
| 503 | } |