Package tech.ydb.yoj.repository.db.cache

Class DbValueUpdater<V>

java.lang.Object

tech.ydb.yoj.repository.db.cache.DbValueUpdater<V>

public abstract class DbValueUpdater<V>
extends Object

Abstract base class for caching rarely updated values, e.g. feature flags.

Each active updater runs a periodic task which retrieves the value and caches it.

Clients should call readCached() to retrieve value cached by an active updater; implementors should override doReadValue() and choose which super constructor to call.

Lifecycle of ValueUpdater instances should be preferably managed by some external framework, e.g., Spring lifecycle. We recommend that you call start() at application start/component test start and shutdown() at graceful shutdown/component test shutdown.

See Also:

• start()
• shutdown()
• readCached()
• doReadValue()

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	DbValueUpdater.ThreadFactoryCreator

Field Summary

Fields

Modifier and Type	Field	Description
protected static final Duration	DEFAULT_CACHE_TIMEOUT
protected static final Duration	DEFAULT_MAX_LAG
protected static final Duration	DEFAULT_MAX_READ_DURATION
protected static final Duration	DEFAULT_SHUTDOWN_TIMEOUT
protected static final DbValueUpdater.ThreadFactoryCreator	DEFAULT_THREAD_FACTORY_CREATOR
protected static final org.slf4j.Logger	log
protected final Duration	maxAge
protected final Duration	maxReadDuration
protected final String	name
protected final Duration	pollInterval
protected final Duration	shutdownTimeout
protected final ThreadFactory	threadFactory

Constructor Summary

Constructors

Constructor	Description
DbValueUpdater()
DbValueUpdater(@NonNull String name, @NonNull Duration pollInterval, @NonNull Duration shutdownTimeout, @NonNull Duration maxAge, @NonNull Duration maxReadDuration)
DbValueUpdater(@NonNull String name, @NonNull Duration pollInterval, @NonNull Duration shutdownTimeout, @NonNull Duration maxAge, @NonNull Duration maxReadDuration, @NonNull DbValueUpdater.ThreadFactoryCreator threadFactorySupplier)
DbValueUpdater(@NonNull Duration pollInterval, @NonNull Duration shutdownTimeout, @NonNull Duration maxAge, @NonNull Duration maxReadDuration)
DbValueUpdater(@NonNull Duration pollInterval, @NonNull Duration shutdownTimeout, @NonNull Duration maxAge, @NonNull Duration maxReadDuration, @NonNull Function<DbValueUpdater<V>,String> nameSupplier, @NonNull DbValueUpdater.ThreadFactoryCreator threadFactoryCreator)
DbValueUpdater(@NonNull Duration pollInterval, @NonNull Duration shutdownTimeout, @NonNull Duration maxAge, @NonNull Duration maxReadDuration, @NonNull DbValueUpdater.ThreadFactoryCreator threadFactorySupplier)
DbValueUpdater(@NonNull ThreadFactory threadFactory)
DbValueUpdater(@NonNull DbValueUpdater.ThreadFactoryCreator threadFactorySupplier)

Method Summary

Modifier and Type	Method	Description
protected abstract V	doReadValue()
void	forceUpdate()	Forces an immediate value update.
boolean	isUpdaterActive()	Checks if updater is active
V	readCached()
void	shutdown()
void	start()
String	toString()
protected V	tryReadValue()

Methods inherited from class java.lang.Object

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

Field Details

log

protected static final org.slf4j.Logger log

DEFAULT_THREAD_FACTORY_CREATOR

protected static final DbValueUpdater.ThreadFactoryCreator DEFAULT_THREAD_FACTORY_CREATOR

DEFAULT_CACHE_TIMEOUT

protected static final Duration DEFAULT_CACHE_TIMEOUT

DEFAULT_SHUTDOWN_TIMEOUT

protected static final Duration DEFAULT_SHUTDOWN_TIMEOUT

DEFAULT_MAX_LAG

protected static final Duration DEFAULT_MAX_LAG

DEFAULT_MAX_READ_DURATION

protected static final Duration DEFAULT_MAX_READ_DURATION

pollInterval

protected final Duration pollInterval

shutdownTimeout

protected final Duration shutdownTimeout

maxAge

protected final Duration maxAge

maxReadDuration

protected final Duration maxReadDuration

threadFactory

protected final ThreadFactory threadFactory

name

protected final String name

Constructor Details

DbValueUpdater

public DbValueUpdater()

DbValueUpdater

public DbValueUpdater(@NonNull
 @NonNull ThreadFactory threadFactory)

DbValueUpdater

public DbValueUpdater(@NonNull
 @NonNull Duration pollInterval,
 @NonNull
 @NonNull Duration shutdownTimeout,
 @NonNull
 @NonNull Duration maxAge,
 @NonNull
 @NonNull Duration maxReadDuration)

DbValueUpdater

public DbValueUpdater(@NonNull
 @NonNull String name,
 @NonNull
 @NonNull Duration pollInterval,
 @NonNull
 @NonNull Duration shutdownTimeout,
 @NonNull
 @NonNull Duration maxAge,
 @NonNull
 @NonNull Duration maxReadDuration)

DbValueUpdater

public DbValueUpdater(@NonNull
 @NonNull DbValueUpdater.ThreadFactoryCreator threadFactorySupplier)

DbValueUpdater

public DbValueUpdater(@NonNull
 @NonNull Duration pollInterval,
 @NonNull
 @NonNull Duration shutdownTimeout,
 @NonNull
 @NonNull Duration maxAge,
 @NonNull
 @NonNull Duration maxReadDuration,
 @NonNull
 @NonNull DbValueUpdater.ThreadFactoryCreator threadFactorySupplier)

DbValueUpdater

public DbValueUpdater(@NonNull
 @NonNull String name,
 @NonNull
 @NonNull Duration pollInterval,
 @NonNull
 @NonNull Duration shutdownTimeout,
 @NonNull
 @NonNull Duration maxAge,
 @NonNull
 @NonNull Duration maxReadDuration,
 @NonNull
 @NonNull DbValueUpdater.ThreadFactoryCreator threadFactorySupplier)

DbValueUpdater

public DbValueUpdater(@NonNull
 @NonNull Duration pollInterval,
 @NonNull
 @NonNull Duration shutdownTimeout,
 @NonNull
 @NonNull Duration maxAge,
 @NonNull
 @NonNull Duration maxReadDuration,
 @NonNull
 @NonNull Function<DbValueUpdater<V>,String> nameSupplier,
 @NonNull
 @NonNull DbValueUpdater.ThreadFactoryCreator threadFactoryCreator)

Method Details

doReadValue

@NonNull
protected abstract V doReadValue()

Returns:

value to cache; must not be null

start

public void start()

shutdown

public void shutdown()

isUpdaterActive

public boolean isUpdaterActive()

Checks if updater is active

Returns:

true if updater is active (cachedValue not null), else false

readCached

@NonNull
public V readCached()

Returns:

cached value

Throws:

IllegalStateException - if value updater is not active

forceUpdate

public void forceUpdate()

Forces an immediate value update. Will throw if the value cannot be updated.
This method should ONLY be used in tests.

toString

public String toString()

Overrides:

toString in class Object

tryReadValue

@Nullable
protected V tryReadValue()