Package org.apache.sling.discovery.commons.providers.spi.base

Class SyncTokenService

java.lang.Object

org.apache.sling.discovery.commons.providers.spi.base.AbstractServiceWithBackgroundCheck

org.apache.sling.discovery.commons.providers.spi.base.SyncTokenService

All Implemented Interfaces:

ClusterSyncService

public class SyncTokenService
extends AbstractServiceWithBackgroundCheck
implements ClusterSyncService

Implements the syncToken idea: each instance stores a key-value pair with key=stringId and value=discoveryLiteSequenceNumber under /var/discovery/oak/syncTokens - and then waits until it sees the same token from all other instances in the cluster. This way, once the syncToken is received the local instance knows that all instances in the cluster are now in TOPOLOGY_CHANGING state (thus all topology-dependent activity is now stalled and waiting) and are aware of the new discoveryLite view.

Field Summary

Fields

Modifier and Type	Field	Description
protected ClusterSyncHistory	clusterSyncHistory
protected DiscoveryLiteConfig	commonsConfig
protected ResourceResolverFactory	resourceResolverFactory
protected SlingSettingsService	settingsService

Fields inherited from class org.apache.sling.discovery.commons.providers.spi.base.AbstractServiceWithBackgroundCheck

backgroundCheckRunnable, logger, slingId

Constructor Summary

Constructors

Constructor	Description
SyncTokenService()

Method Summary

Modifier and Type	Method	Description
protected void	activate()
void	cancelSync()
ClusterSyncHistory	getClusterSyncHistory()
protected ResourceResolver	getResourceResolver()	Get or create a ResourceResolver
void	setConsistencyHistory(ClusterSyncHistory consistencyHistory)
void	sync(BaseTopologyView view, Runnable callback)	Starts the synchronization process and calls the provided callback upon completion.
protected void	syncToken(BaseTopologyView view, Runnable callback)
static SyncTokenService	testConstructor(DiscoveryLiteConfig commonsConfig, ResourceResolverFactory resourceResolverFactory, SlingSettingsService settingsService)
static SyncTokenService	testConstructorAndActivate(DiscoveryLiteConfig commonsConfig, ResourceResolverFactory resourceResolverFactory, SlingSettingsService settingsService)

Methods inherited from class org.apache.sling.discovery.commons.providers.spi.base.AbstractServiceWithBackgroundCheck

cancelPreviousBackgroundCheck, startBackgroundCheck, triggerBackgroundCheck

Methods inherited from class java.lang.Object

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

Field Details

commonsConfig

protected DiscoveryLiteConfig commonsConfig

resourceResolverFactory

protected ResourceResolverFactory resourceResolverFactory

settingsService

protected SlingSettingsService settingsService

clusterSyncHistory

protected ClusterSyncHistory clusterSyncHistory

Constructor Details

SyncTokenService

public SyncTokenService()

Method Details

testConstructorAndActivate

public static SyncTokenService testConstructorAndActivate(DiscoveryLiteConfig commonsConfig,
 ResourceResolverFactory resourceResolverFactory,
 SlingSettingsService settingsService)

testConstructor

public static SyncTokenService testConstructor(DiscoveryLiteConfig commonsConfig,
 ResourceResolverFactory resourceResolverFactory,
 SlingSettingsService settingsService)

activate

protected void activate()

setConsistencyHistory

public void setConsistencyHistory(ClusterSyncHistory consistencyHistory)

getClusterSyncHistory

public ClusterSyncHistory getClusterSyncHistory()

getResourceResolver

protected ResourceResolver getResourceResolver()
                                        throws LoginException

Get or create a ResourceResolver

Throws:

LoginException

cancelSync

public void cancelSync()

Specified by:

cancelSync in interface ClusterSyncService

sync

public void sync(BaseTopologyView view,
 Runnable callback)

Description copied from interface: ClusterSyncService

Starts the synchronization process and calls the provided callback upon completion.

sync() is not thread-safe and should not be invoked concurrently.

If sync() gets called before a previous invocation finished, that previous invocation will be discarded, ie the callback of the previous invocation will no longer be called.

The synchronization process consists of making sure that the repository has processed any potential backlog of instances that are no longer part of the provided, new view. Plus it writes a 'sync-token' to a well-defined location, with all peers doing the same, and upon seeing all other sync-tokens declares successful completion - at which point it calls the callback.run().

Specified by:

sync in interface ClusterSyncService

Parameters:

view - the view which all instances in the local cluster should agree on having seen

callback - the runnable which should be called after successful syncing

syncToken

protected void syncToken(BaseTopologyView view,
 Runnable callback)