Package io.deephaven.persistence

Class PersistencePolicy

java.lang.Object

io.deephaven.persistence.PersistencePolicy

public class PersistencePolicy
extends Object

Persistence policy for persistent storage implementations. This indicates how often checkpoints should be committed. It assumes nothing about the implementation that uses the policy.

Constructor Summary

Constructors

Constructor	Description
PersistencePolicy(int maxUpdateCount)	Create a persistence policy that is based on the number of updates since the last checkpoint commit.
PersistencePolicy(int idleSinceCommitSeconds, int idleSinceUpdateSeconds, int forcedCommitTimeoutSeconds)	Create a PersistencePolicy using timeout mode.

Method Summary

Modifier and Type	Method	Description
void	committedNow()	Indicate that a checkpoint commit has been performed.
int	getCheckpointBufferSize()	Return the specified checkpoint buffer size.
boolean	needToCommit()	Indicates whether or not the policy indicates that a checkpoint commit is required.
boolean	shouldWriteUpdates()	Indicate whether or not all updates should be persisted.
void	updatedNow()	Indicate that an uncommitted update has been performed.

Methods inherited from class java.lang.Object

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

Constructor Details

PersistencePolicy

public PersistencePolicy(int idleSinceCommitSeconds,
 int idleSinceUpdateSeconds,
 int forcedCommitTimeoutSeconds)

Create a PersistencePolicy using timeout mode. The timeout mode is based on three timeout parameters. For example:
new PersistencePolicy(20, 5, 120)

This commits every 20 seconds if you've been idle for 5 seconds, commit every 120 seconds even if you haven't been idle.

Parameters:

idleSinceCommitSeconds - the required idle time (in seconds) since the last commit before a checkpoint commit must be made

idleSinceUpdateSeconds - the required idle time (in seconds) since the last update before a checkpoint commit must be made

forcedCommitTimeoutSeconds - the time (in seconds) after which a checkpoint commit must be made if any updates have been done

PersistencePolicy

public PersistencePolicy(int maxUpdateCount)

Create a persistence policy that is based on the number of updates since the last checkpoint commit. If maxUpdateCount is exceeded, a checkpoint commit is required.

Parameters:

maxUpdateCount - the number of updates required before a checkpoint commit is required

Method Details

committedNow

public void committedNow()

Indicate that a checkpoint commit has been performed. This should be called by the implementation whenever a checkpoint commit is performed, to reset the policy's counts and timings.

updatedNow

public void updatedNow()

Indicate that an uncommitted update has been performed. This should be called every time an operation is performed that needs to be persisted.

needToCommit

public boolean needToCommit()

Indicates whether or not the policy indicates that a checkpoint commit is required. In all cases, if no updates have been made, then no checkpoint commit is required. The logic is based on the mode.

• Update count mode - return true if the number of updates exceeds the maximum update count.
• Timeout mode - return true if at least one update has been made, and either:
  • The time since the last commit exceeds the specified force commit timeout
  • The idle time since the last update exceeds the previously-specified idleSinceUpdateSeconds, and the idle time since the last commit exceeds the required idleSinceCommitSeconds

Returns:

true if a checkpoint commit is required, false otherwise

shouldWriteUpdates

public boolean shouldWriteUpdates()

Indicate whether or not all updates should be persisted. If this is not true, then some updates may be lost.

Returns:

true if all updates should be tracked, false if it is acceptable to lose updates

getCheckpointBufferSize

public int getCheckpointBufferSize()

Return the specified checkpoint buffer size.

Returns:

the checkpoint buffer size in bytes