Package org.apache.bookkeeper.client

Class MetadataUpdateLoop

java.lang.Object

org.apache.bookkeeper.client.MetadataUpdateLoop

class MetadataUpdateLoop
extends Object

Mechanism to safely update the metadata of a ledger.

The loop takes the following steps: 1. Check if the metadata needs to be changed. 2. Make a copy of the metadata and modify it. 3. Write the modified copy to zookeeper. 3.1 If the write succeeds, go to 6. 3.2 If the write fails because of a failed compare and swap, go to 4. 4. Read the metadata back from the store 5. Update the local copy of the metadata with the metadata read in 4, go to 1. 6. Update the local copy of the metadata with the metadata which has just been written.

All mutating operations are compare and swap operation. If the compare fails, another iteration of the loop begins.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
(package private) static interface	MetadataUpdateLoop.LocalValueUpdater
(package private) static interface	MetadataUpdateLoop.MetadataTransform
(package private) static interface	MetadataUpdateLoop.NeedsUpdatePredicate

Field Summary

Fields

Modifier and Type	Field	Description
(package private) static final org.slf4j.Logger	LOG

Constructor Summary

Constructors

Constructor	Description
MetadataUpdateLoop(LedgerManager lm, long ledgerId, Supplier<Versioned<LedgerMetadata>> currentLocalValue, MetadataUpdateLoop.NeedsUpdatePredicate needsTransformation, MetadataUpdateLoop.MetadataTransform transform, MetadataUpdateLoop.LocalValueUpdater updateLocalValue)
MetadataUpdateLoop(LedgerManager lm, long ledgerId, Supplier<Versioned<LedgerMetadata>> currentLocalValue, MetadataUpdateLoop.NeedsUpdatePredicate needsTransformation, MetadataUpdateLoop.MetadataTransform transform, MetadataUpdateLoop.LocalValueUpdater updateLocalValue, com.google.common.util.concurrent.RateLimiter throttler)	Construct the loop.

Method Summary

Modifier and Type	Method	Description
(package private) CompletableFuture<Versioned<LedgerMetadata>>	run()

Methods inherited from class java.lang.Object

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

Field Details

LOG

static final org.slf4j.Logger LOG

Constructor Details

MetadataUpdateLoop

MetadataUpdateLoop(LedgerManager lm,
 long ledgerId,
 Supplier<Versioned<LedgerMetadata>> currentLocalValue,
 MetadataUpdateLoop.NeedsUpdatePredicate needsTransformation,
 MetadataUpdateLoop.MetadataTransform transform,
 MetadataUpdateLoop.LocalValueUpdater updateLocalValue)

MetadataUpdateLoop

MetadataUpdateLoop(LedgerManager lm,
 long ledgerId,
 Supplier<Versioned<LedgerMetadata>> currentLocalValue,
 MetadataUpdateLoop.NeedsUpdatePredicate needsTransformation,
 MetadataUpdateLoop.MetadataTransform transform,
 MetadataUpdateLoop.LocalValueUpdater updateLocalValue,
 com.google.common.util.concurrent.RateLimiter throttler)

Construct the loop. This takes a set of functions which may be called multiple times during the loop.

Parameters:

lm - the ledger manager used for reading and writing metadata

ledgerId - the id of the ledger we will be operating on

currentLocalValue - should return the current local value of the metadata

needsTransformation - should return true, if the metadata needs to be modified. should throw an exception, if this update doesn't make sense.

transform - takes a metadata objects, transforms, and returns it, without modifying the original

updateLocalValue - if the local value matches the first parameter, update it to the second parameter and return true, return false otherwise

Method Details

run

CompletableFuture<Versioned<LedgerMetadata>> run()