org.apache.cassandra.db.lifecycle

Class TransactionLog

java.lang.Object

org.apache.cassandra.utils.concurrent.Transactional.AbstractTransactional

org.apache.cassandra.db.lifecycle.TransactionLog

All Implemented Interfaces:

java.lang.AutoCloseable, Transactional

public class TransactionLog
extends Transactional.AbstractTransactional
implements Transactional

IMPORTANT: When this object is involved in a transactional graph, and is not encapsulated in a LifecycleTransaction, for correct behaviour its commit MUST occur before any others, since it may legitimately fail. This is consistent with the Transactional API, which permits one failing action to occur at the beginning of the commit phase, but also *requires* that the prepareToCommit() phase only take actions that can be rolled back. A class that tracks sstable files involved in a transaction across sstables: if the transaction succeeds the old files should be deleted and the new ones kept; vice-versa if it fails. The transaction log file contains new and old sstables as follows: add:[sstable-2][CRC] remove:[sstable-1,max_update_time,num files][CRC] where sstable-2 is a new sstable to be retained if the transaction succeeds and sstable-1 is an old sstable to be removed. CRC is an incremental CRC of the file content up to this point. For old sstable files we also log the last update time of all files for the sstable descriptor and a checksum of vital properties such as update times and file sizes. Upon commit we add a final line to the log file: commit:[commit_time][CRC] When the transaction log is cleaned-up by the TransactionTidier, which happens only after any old sstables have been osoleted, then any sstable files for old sstables are removed before deleting the transaction log if the transaction was committed, vice-versa if the transaction was aborted. On start-up we look for any transaction log files and repeat the cleanup process described above. See CASSANDRA-7066 for full details.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	TransactionLog.CorruptTransactionLogException If the format of the lines in the transaction log is wrong or the checksum does not match, then we throw this exception.
static class	TransactionLog.RecordType
static class	TransactionLog.SSTableTidier The SSTableReader tidier.

Nested classes/interfaces inherited from class org.apache.cassandra.utils.concurrent.Transactional.AbstractTransactional

Transactional.AbstractTransactional.State

Nested classes/interfaces inherited from interface org.apache.cassandra.utils.concurrent.Transactional

Transactional.AbstractTransactional

Method Summary

Modifier and Type	Method and Description
protected java.lang.Throwable	doAbort(java.lang.Throwable accumulate)
protected java.lang.Throwable	doCommit(java.lang.Throwable accumulate)
protected void	doPrepare() Do any preparatory work prior to commit.
static void	rescheduleFailedDeletions() Retry all deletions that failed the first time around (presumably b/c the sstable was still mmap'd.) Useful because there are times when we know GC has been invoked; also exposed as an mbean.
static void	waitForDeletions() Deletions run on the nonPeriodicTasks executor, (both failedDeletions or global tidiers in SSTableReader) so by scheduling a new empty task and waiting for it we ensure any prior deletion has completed.

Methods inherited from class org.apache.cassandra.utils.concurrent.Transactional.AbstractTransactional

abort, abort, close, commit, commit, doPostCleanup, doPreCleanup, finish, permitRedundantTransitions, prepareToCommit, state

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.cassandra.utils.concurrent.Transactional

abort, commit, prepareToCommit

Methods inherited from interface java.lang.AutoCloseable

close

Method Detail

rescheduleFailedDeletions

public static void rescheduleFailedDeletions()

Retry all deletions that failed the first time around (presumably b/c the sstable was still mmap'd.) Useful because there are times when we know GC has been invoked; also exposed as an mbean.

waitForDeletions

public static void waitForDeletions()

Deletions run on the nonPeriodicTasks executor, (both failedDeletions or global tidiers in SSTableReader) so by scheduling a new empty task and waiting for it we ensure any prior deletion has completed.

doCommit

protected java.lang.Throwable doCommit(java.lang.Throwable accumulate)

Specified by:

doCommit in class Transactional.AbstractTransactional

doAbort

protected java.lang.Throwable doAbort(java.lang.Throwable accumulate)

Specified by:

doAbort in class Transactional.AbstractTransactional

doPrepare

protected void doPrepare()

Description copied from class: Transactional.AbstractTransactional

Do any preparatory work prior to commit. This method should throw any exceptions that can be encountered during the finalization of the behaviour.

Specified by:

doPrepare in class Transactional.AbstractTransactional