com.sleepycat.je.dbi

Class BackupManager

java.lang.Object

com.sleepycat.je.dbi.BackupManager

public class BackupManager
extends Object

Manages automatic backups.

Automatic backups can scheduled by setting the appropriate environment variables:

• EnvironmentConfig.ENV_RUN_BACKUP
• EnvironmentConfig.BACKUP_SCHEDULE
• EnvironmentConfig.BACKUP_COPY_CLASS
• EnvironmentConfig.BACKUP_COPY_CONFIG
• EnvironmentConfig.BACKUP_LOCATION_CLASS
• EnvironmentConfig.BACKUP_LOCATION_CONFIG

The backups are performed using the DbBackup class. Each backup creates a snapshot with hard links to log files from DbBackup.

The files are then copied to an archive location. Only new (or newly modified) files are copied for each snapshot. The copy mechanism maintains a manifest for each snapshot that documents its contents and is used to determine which files have already been copied. After a log file is copied, the associated hard link is removed so that the file can be deleted from disk as needed. When a local snapshot is no longer needed, it is deleted.

The backup is performed by two separate threads. SnapshotThread creates JE snapshots on the configured schedule. It runs as its own thread so that backups are performed as close as possible to the scheduled time, to allow backups for different environments to be coordinated. When a snapshot has been created, the snapshot thread wakes up CopyThread, which copies the snapshot to archive storage. If the copy thread is still running when the snapshot thread creates a new snapshot, the snapshot thread interrupts the copy thread so that it will abandon its work on that snapshot and start work on the new one.

Field Summary

Fields

Modifier and Type	Field and Description
static String	SNAPSHOT_MANIFEST The name of the manifest file created in a snapshot directory to represent the copy status of files in the snapshot.
static long	timeMultiplier If non-zero, a multiplier to speed the passage of time by the specified factor, for testing only.

Constructor Summary

Constructors

Constructor and Description
BackupManager(EnvironmentImpl envImpl) Creates an instance of this class for the specified environment.

Method Summary

Modifier and Type	Method and Description
static String	checksumToHex(byte[] checksum) Converts a checksum to hex format.
static CronScheduleParser	createSnapshotScheduleParser(String cronSchedule) Processes information in the specified crontab formatted schedule.
static long	currentTimeMs() Returns the current time in absolute milliseconds, adjusted as needed for timeMultiplier.
static void	forceFile(Path path) Force any pending changes to disk for the file with the specified pathname.
static <C> Constructor<? extends C>	getImplementationClassConstructor(Class<? extends C> type, String className) Returns a public no-arguments constructor for a non-abstract class that implements the specified interface.
static <C> C	getImplementationInstance(Class<C> type, String className) Returns an object that implements an interface by creating an instance of the specified non-abstract class that implements the specified interface.
static void	sleepMs(long timeMs) Sleeps for the specified number of milliseconds, adjusted as needed for timeMultiplier.

Methods inherited from class java.lang.Object

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

Field Detail

timeMultiplier

public static volatile long timeMultiplier

If non-zero, a multiplier to speed the passage of time by the specified factor, for testing only. Some possible settings:

• One hour takes a second: 60*60 = 3600
• One day takes a second: 60*60*24 = 86400
• One week takes a second: 60*60*24*7 = 604800

Note that the resulting time value needs to be less than Long.MAX_VALUE. With the current time of around 1528719052059 and a max value of 9223372036854775807, that makes the maximum multiplier approximately 6 million. The one week to a second transformation should continue to work as long as we could possibly care about -- until 2453!

Waiting for an amount of time that, because of the multiplier, is less than 1 millisecond will result in a 1 millisecond wait. Tests need to account for the fact that seemingly short operations may take a long time in the dilated time scale.

Code in this file (and in tests) that needs the current time should call currentTimeMs(), call waitMs(java.lang.Object, long) to wait, and call sleepMs(long) to sleep. These three methods apply the time multiplier if specified.

SNAPSHOT_MANIFEST

public static final String SNAPSHOT_MANIFEST

The name of the manifest file created in a snapshot directory to represent the copy status of files in the snapshot.

See Also:

Constant Field Values

Constructor Detail

BackupManager

public BackupManager(EnvironmentImpl envImpl)

Creates an instance of this class for the specified environment.

Parameters:

envImpl - the environment

Throws:

IllegalArgumentException - if there is a problem with a configuration property

Method Detail

createSnapshotScheduleParser

public static CronScheduleParser createSnapshotScheduleParser(String cronSchedule)

Processes information in the specified crontab formatted schedule.

Parameters:

cronSchedule - the schedule

Returns:

information about the schedule

Throws:

IllegalArgumentException - if the schedule is illegal

forceFile

public static void forceFile(Path path)
                      throws IOException

Force any pending changes to disk for the file with the specified pathname. Use this on the directory path to force directory changes for renames or deletes.

Parameters:

path - the file path

Throws:

IOException - if an I/O failure occurs TODO: Move this method to some je utility package where it would be available for more general use.

getImplementationClassConstructor

public static <C> Constructor<? extends C> getImplementationClassConstructor(Class<? extends C> type,
                                                                             String className)

Returns a public no-arguments constructor for a non-abstract class that implements the specified interface.

Type Parameters:

C - the interface type

Parameters:

type - the interface that the class must implement

className - the fully qualified class name

Returns:

the constructor

Throws:

IllegalStateException - if type is not an interface, the specified class is not found, does not implement the specified interface, is abstract, or does not have a public no-arguments constructor

getImplementationInstance

public static <C> C getImplementationInstance(Class<C> type,
                                              String className)

Returns an object that implements an interface by creating an instance of the specified non-abstract class that implements the specified interface.

Type Parameters:

C - the interface type

Parameters:

type - the interface that the class must implement

className - the fully qualified class name

Returns:

an instance of the class

Throws:

IllegalStateException - if type is not an interface, the specified class is not found, does not implement the specified interface, is abstract, does not have a public no-arguments constructor, or the call to the constructor throws an exception

currentTimeMs

public static long currentTimeMs()

Returns the current time in absolute milliseconds, adjusted as needed for timeMultiplier.

Returns:

the current adjusted absolute time

sleepMs

public static void sleepMs(long timeMs)
                    throws InterruptedException

Sleeps for the specified number of milliseconds, adjusted as needed for timeMultiplier.

Parameters:

timeMs - the number of milliseconds to sleep

Throws:

IllegalArgumentException - if timeMs is less than 1

InterruptedException - if the operation is interrupted

checksumToHex

public static String checksumToHex(byte[] checksum)

Converts a checksum to hex format.

Parameters:

checksum - the checksum as a byte array

Returns:

the checksum as a string in hex format