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Repository OSGi Configuration

Oak comes with a simple mechanism for constructing content repositories for use in embedded deployments and test cases. Details regarding that are provided as part of Repository Construction. When used in OSGi environment then various Oak components can be configured using OSGi Configuration Support.

Depending on component the configuration can be modified at runtime or needs to be specified before the initial system setup.

Static Configuration
Such configuration settings cannot be changed once a repository is initialized. For example choosing a DataStore or specifying the path of User Home. Such properties should not be changed once a system is initialized.
Dynamic Configuration
Some of the configuration settings like thread pool size, cache size etc can be changed at runtime or after initial system setup

Each OSGi configuration is referred via a PID i.e. persistent identifier. Sections below provide details around various PID used in Oak

NodeStore

SegmentNodeStore

This section describes the configuration for the Segment Node Store, an implementation of the Node Store that saves repository data on disk.

The first of these configurations, identified by org.apache.jackrabbit.oak.segment.SegmentNodeStoreService, refers to the implementation provided by the oak-segment-tar bundle. This implementation is the newest and the only actively maintained one, and should be used unless some legacy use case needs to be supported.

The second and last configuration, identified by org.apache.jackrabbit.oak.plugins.segment.SegmentNodeStoreService, refers to the old implementation of the Node Store provided by the oak-segment bundle. This implementation has been deprecated, will not receive any further improvements and should not be used, if possible.

org.apache.jackrabbit.oak.segment.SegmentNodeStoreService
repository.home (string) - repository
A path on the file system where repository data will be stored. The Segment Store persists its data in a subdirectory of repository.home named segmentstore. The provided path can be relative or absolute. If a relative path is provided, it is handled according to the definition of relative path as specified by java.io.File. Placeholders of any kind in the path are not supported.
tarmk.mode (string) - 64
The architecture model. It can assume only two values, 32 or 64. If this property is set to 64, data files used by the Segment Store are memory-mapped. Any other value will instruct the Segment Store not to use memory-mapped files.
tarmk.size (int) - 256
The maximum size of TAR files on disk in MB.
segmentCache.size (int) - 256
The maximum size of the segment cache in MB. The segment cache keeps a subset of the segments in memory and avoids performing I/O operations when those segments are used.
stringCache.size (int) - 256
The maximum size of the strings cache in MB. The string cache keeps a subset of the string records in memory and avoids performing I/O operations when those strings are used.
templateCache.size (int) - 256
The maximum size of the template cache in MB. The template cache keeps a subset of the template records in memory and avoids performing I/O operations when those templates are used.
stringDeduplicationCache.size (int) - 15000
The maximum size of the string deduplication cache in number of items. The string deduplication cache tracks string records across different GC generations. It avoids duplicating a string record to the current GC generation if it was already duplicated in the past.
templateDeduplicationCache.size (int) - 3000
The maximum size of the template deduplication cache in number of items. The template deduplication cache tracks template records across different GC generations. It avoids duplicating a template record to the current GC generation if it was already duplicated in the past.
nodeDeduplicationCache.size (int) - 1048576
The maximum size of the node deduplication cache in number of items. The node deduplication cache tracks node records across different GC generations. It avoids duplicating a node record to the current generation if it was already duplicated in the past.
pauseCompaction (boolean) - false
Determines if online compaction should be executed. If this property is true, both the estimation and compaction phases of the online compaction process are not executed.
compaction.retryCount (int) - 5
The number of commit attempts the online compaction process should try before giving up. This property determines how many times the online compaction process should try to merge the compacted repository state with the user-generated state produced by commits executed concurrently during compaction.
compaction.force.timeout (int) - 60
The amount of time the online compaction process is allowed to exclusively lock the store, in seconds. If this property is set to a positive value, if the compaction process fails to commit the compacted state concurrently with other commits, it will acquire an exclusive lock on the Node Store. The exclusive lock prevents other commits for completion, giving the compaction process a possibility to commit the compacted state. This property determines how long the compaction process is allowed to use the Node Store in exclusive mode. If this property is set to zero or to a negative value, the compaction process will not acquire an exclusive lock on the Node Store and will just give up if too many concurrent commits are detected.
compaction.sizeDeltaEstimation (long) - 10737418240
The increase in size of the Node Store (in bytes) since the last successful compaction that will trigger another execution of the compaction phase.
compaction.disableEstimation (boolean) - false
Disables the estimation phase of the online compaction process. If this property is set to true, the estimation phase of the compaction process will never run, and compaction will always be triggered for any amount of garbage in the Node Store.
compaction.retainedGenerations (int) - 2
The number of generations to retain the Node Store.
compaction.memoryThreshold (int) - 15
The percentage of heap memory that should always be free while compaction runs. If the available heap memory falls below the specified percentage, compaction will not be started or it will be aborted if it is already running.
compaction.progressLog (long) - -1
Enables compaction progress logging at each set of compacted nodes. A value of -1 disables the log.
standby (boolean) - false
Determines if this Node Store is supposed to be used in standby mode.
customBlobStore (boolean) - false
Determines if this Node Store is supposed to use a custom Blob Store. If this property is true, a Data Store or a Blob Store needs to be configured for the Segment Store to pick it up (see below). If this property is false, binaries will be stored in the Segment Store.
repository.backup.dir (string)
The path on the file system where backups of this Node Store should be stored. It defaults to a subdirectory of repository.home named segmentstore-backup. If a relative path is provided, it is handled according to the definition of relative path as specified by java.io.File. Placeholders of any kind in the path are not supported.
org.apache.jackrabbit.oak.plugins.segment.SegmentNodeStoreService

This configuration is deprecated. It belongs to the legacy Node Store implementation provided by the oak-segment bundle. This implementation should not be used anymore. Instead, rely on the Node Store implementation provided by the oak-segment-tar bundle, whose configuration is described above.

repository.home (string) - tarmk
A path on the file system where repository data will be stored. The Segment Store persists its data in a subdirectory of repository.home named segmentstore. The provided path can be relative or absolute. If a relative path is provided, it is handled according to the definition of relative path as specified by java.io.File. Placeholders of any kind in the path are not supported.
tarmk.mode (string) - 64
The architecture model. It can assume only two values, 32 or 64. If this property is set to 64, data files used by the Segment Store are memory-mapped. Any other value will instruct the Segment Store not to use memory-mapped files.
tarmk.size (int) - 256
Maximum file size (in MB).
cache (int) - 256
Size of the segment cache in MB.
compaction.cloneBinaries (boolean) - false
Determines if binaries should be cloned when performing online compaction.
compaction.cleanup (string) - CLEAN_OLD
Determines how in-memory references to persisted data might influence the outcome of online compaction. It can only assume the values CLEAN_ALL, CLEAN_OLD and CLEAN_NONE. If this property is CLEAN_ALL, every memory reference is ignored. If this property is CLEAN_OLD, only memory references newer than a certain timestamp are considered (see compaction.cleanup.timestamp). If this property is CLEAN_NONE, no data pointed to by an in-memory reference will be cleaned up.
compaction.cleanup.timestamp (long) - 36000000
The expiry time for in-memory references in ms. If CLEAN_OLD is used as the value of the compaction.cleanup property, every piece of data pointed to by a reference newer than this time interval will not be considered eligible for compaction.
compaction.memoryThreshold (byte) - 5
A multiplier to help in estimating the amount of memory needed for compaction. Setting this property to 0 indirectly skips compaction because not enough memory is available.
compaction.gainThreshold (byte) - 10.
A percentage, expressed as an integer between 0 and 100, representing the expected gain of online compaction. If the amount of garbage is not equals to or greater than this percentage of the total disk space occupied by the Node Store, compaction will not run. Setting this property to 0 or to a negative value indirectly disables the estimation phase of the online compaction process.
pauseCompaction (boolean) - true
Determines if online compaction should be executed. If this property is true, both the estimation and compaction phases of the online compaction process are not executed.
compaction.retryCount (int) - 5
The number of commit attempts the online compaction process should try before giving up. It defaults to 5. This property determines how many times the online compaction process should try to merge the compacted repository state with the user-generated state produced by commits executed concurrently during compaction.
compaction.forceAfterFail (boolean) - false
Determines if online compaction should force its commit after a certain amount of attempts.
compaction.lockWaitTime (int) - 60
Determines how long (in seconds) online compaction can use the Node Store in exclusive mode. It defaults to 60. This value determines the validity of the exclusive lock on the Node Store acquired by the online compaction process when forcing its commit.
persistCompactionMap (boolean) - true
Determines if the compaction map should be persisted on disk.
standby (boolean) - false
Determines if this Node Store should be started in standby mode.
secondary (boolean) - false
Determines if this Node Store should be started as a secondary store.
customBlobStore (boolean) - false
Determines if this Node Store is supposed to use a custom Blob Store. If this property is true, a Data Store or a Blob Store needs to be configured for the Segment Store to pick it up (see below). If this property is false, binaries will be stored in the Segment Store.
blobGcMaxAgeInSecs (long) - 86400
BLOB Garbage Collector (GC) logic would only consider those BLOBs for GC which are not accessed recently (currentTime - lastModifiedTime > blobGcMaxAgeInSecs). For example, as per default, only those BLOBs which have been created 24 hours in the past would be considered for GC. It is strongly advised to not set this property to a very low value of say a few minutes but only set it to a hour at a minimum. This is to ensure that the NodeStore(s) have had the time to flush out its internal data structures to persistence and the references to recently added blobs are accounted.
blobTrackSnapshotIntervalInSecs (long) - 43200
The blob ids cached/tracked locally are synchronized with the DataStore at this interval. Any additions and deletions will be visible to other cluster nodes or repositories connected to the shared DatStore after this. This should be less than the blobGcMaxAgeInSecs parameter above and the frequency of blob gc. See Blob tracker.

DocumentNodeStore

PID org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreService

mongouri
Default - mongodb://localhost:27017
Specifies the MongoURI required to connect to Mongo Database
db
Default - oak
Name of the database in Mongo
socketKeepAlive
Default - false
Enables socket keep-alive for MongoDB connections
Since 1.8.0, 1.6.2, 1.4.16
cache
Default - 256
Cache size in MB. This is distributed among various caches used in DocumentNodeStore
changesSize
Default - 256
Size in MB of capped collection used in Mongo for caching the diff output.
customBlobStore
Default false
Boolean value indicating that custom BlobStore to use. By default it uses MongoBlobStore.
maxReplicationLagInSecs
Default 21600 (6 hours)
Determines the duration beyond which it can be safely assumed that state on secondary would be consistent with primary and its safe to read from them. (See OAK-1645)
blobGcMaxAgeInSecs
Default 86400 (24 hrs)
Blob Garbage Collector (GC) logic would only consider those blobs for GC which are not accessed recently (currentTime - lastModifiedTime > blobGcMaxAgeInSecs). For example as per default only those blobs which have been created 24 hrs ago would be considered for GC. It is strongly advised to not set this property to a very low value of say a few minutes but only set it to a hour at a minimum. This is to ensure that the NodeStore(s) have had the time to flush out its internal data structures to persistence and the references to recently added blobs are accounted.
versionGcMaxAgeInSecs
Default 86400 (24 hrs)
Oak uses MVCC model to store the data. So each update to a node results in new version getting created. This duration controls how much old revision data should be kept. For example if a node is deleted at time T1 then its content would only be marked deleted at revision for T1 but its content would not be removed. Only when a Revision GC is run then its content would removed and that too only after (currentTime -T1 > versionGcMaxAgeInSecs)
versionGCContinuous
Default false
Run Revision GC continuously as a scheduled task. By default this is disabled and Revision GC must be triggered by the application when appropriate.
Since 1.7.4
journalGCMaxAge
Default 86400000 (24 hrs, was 6 hrs until 1.7.4)
Journal entries older than journalGCMaxAge can be removed by the journal garbage collector. The maximum age is specified in milliseconds.
Since 1.0.19, 1.2.3, 1.4
journalGCInterval
Default 300000 (5 min)
The interval in milliseconds with which the journal garbage collector removes old journal entries.
Since 1.0.19, 1.2.3, 1.4
blobCacheSize
Default 16 (MB)
DocumentNodeStore when running with Mongo would use MongoBlobStore by default unless a custom BlobStore is configured. In such scenario the size of in memory cache for the frequently used blobs can be configured via blobCacheSize.
persistentCache
Default “cache,binary=0” (prior to 1.6, the persistent cache was disabled by default)
The persistent cache, which is stored in the local file system.
nodeCachePercentage
Default 35 (was 25 until 1.5.14)
Percentage of cache allocated for nodeCache. See Caching
prevDocCachePercentage
Default 4
Percentage of cache allocated for prevDocCache. See Caching
Since 1.3.15
childrenCachePercentage
Default 15 (was 10 until 1.5.14)
Percentage of cache allocated for childrenCache. See Caching
diffCachePercentage
Default 30 (was 5 until 1.5.14)
Percentage of cache allocated for diffCache. See Caching
docChildrenCachePercentage
Default 3
Percentage of cache allocated for docChildrenCache. See Caching
Removed since 1.5.6
cacheSegmentCount
Default 16
The number of segments in the LIRS cache
Since 1.0.15, 1.2.3, 1.3.0
cacheStackMoveDistance
Default 16
The delay to move entries to the head of the queue in the LIRS cache
Since 1.0.15, 1.2.3, 1.3.0
sharedDSRepoId (From Oak 1.2.11, valid for Oak 1.2.x)
Default ""
Custom SharedDataStore repositoryId. Used when custom blobstore configured. Should be unique among the repositories sharing the datastore.
blobTrackSnapshotIntervalInSecs
Default 43200 (12 hrs)
The blob ids cached/tracked locally are synchronized with the DataStore at this interval. Any additions and deletions will be visible to other cluster nodes or repositories connected to the shared DatStore after this. This should be less than the blobGcMaxAgeInSecs parameter above and the frequency of blob gc. See Blob tracker.

Example config file

mongouri=mongodb://localhost:27017
db=oak
Mongo Configuration

All the configuration related to Mongo can be specified via Mongo URI

  • Authentication - Username and password should be specified as part of uri e.g. the following connects and logs in to the admin database as user sysop with the password moon:

    mongodb://sysop:moon@localhost
    
  • Read Preferences and Write Concern - These also can be spcified as part of Mongo URI. Refer to Read Preference and Write Concern section for more details. For e.g. following would set readPreference to secondary and prefer replica with tag dc:ny,rack:1. It would also specify the write timeout to 10 sec

    mongodb://db1.example.net,db2.example.com?readPreference=secondary&readPreferenceTags=dc:ny,rack:1&readPreferenceTags=dc:ny&readPreferenceTags=&w=1&wtimeoutMS=10000    
    

One can also specify the connection pool size, socket timeout etc. For complete details about various possible option refer to Mongo URI

Configuring DataStore/BlobStore

BlobStores are used to store the binary content. Support for Jackrabbit 2 DataStore is also provided via a DataStoreBlobStore wrapper. To use a specific BlobStore implementation following two steps need to be performed

  1. Configure NodeStore - NodeStore config need to be modified to enable use of custom BlobStore via setting customBlobStore to true
  2. Configure BlobStore - Create config for the required BlobStore by using the PID for that BlobStore.

Refer to Config steps in Apache Sling for an example on how to configure a FileDataStore with DocumentNodeStore

Jackrabbit 2 - FileDataStore

Jackrabbit 2 FileDataStore can be configured via following pid

PID org.apache.jackrabbit.oak.plugins.blob.datastore.FileDataStore

path
Default - Not specified
Path to the directory under which the files would be stored.
minRecordLength
Default - 100
Size in bytes. Binary content less than minRecordLength would be inlined i.e. the data store id is the data itself).
maxCachedBinarySize
Default - 17408 (17 KB)
Size in bytes. Binaries with size less than or equal to this size would be stored in in memory cache
cacheSizeInMB
Default - 16
Size in MB. In memory cache for storing small files whose size is less than maxCachedBinarySize. This helps in better performance when lots of small binaries are accessed frequently.
cacheSize
Default - 0
Size in bytes of FileDataStore cache. Cache is enabled when cacheSize > 0. Default is disabled.
cachePath
Default - ${home.dir}/repository/datastore
Path of local file system cache

Jackrabbit 2 - S3DataStore

PID org.apache.jackrabbit.oak.plugins.blob.datastore.S3DataStore

maxCachedBinarySize
Default - 17408 (17 KB)
Size in bytes. Binaries with size less than or equal to this size would be stored in in memory cache
cacheSizeInMB
Default - 16
Size in MB. In memory cache for storing small files whose size is less than maxCachedBinarySize. This helps in better performance when lots of small binaries are accessed frequently.

Oak - SharedS3DataStore (Since Oak 1.2.0)

Supports shared S3 DataStore

PID org.apache.jackrabbit.oak.plugins.blob.datastore.SharedS3DataStore

maxCachedBinarySize
Default - 17408 (17 KB)
Size in bytes. Binaries with size less than or equal to this size would be stored in in memory cache
cacheSizeInMB
Default - 16
Size in MB. In memory cache for storing small files whose size is less than maxCachedBinarySize. This helps in better performance when lots of small binaries are accessed frequently.

Oak - AbstractSharedCachingDataStore (OAK 1.6.x)

All the above data stores enable local file system caching with the following parameters

  • PID org.apache.jackrabbit.oak.plugins.blob.datastore.SharedS3DataStore
  • PID org.apache.jackrabbit.oak.plugins.blob.datastore.S3DataStore
  • PID org.apache.jackrabbit.oak.plugins.blob.datastore.FileDataStore
  • PID org.apache.jackrabbit.oak.plugins.blob.datastore.AzureDataStore
cacheSize
Default - 68719476736
Size in bytes of DataStore cache. Cache is disabled when cacheSize <= 0.
stagingSplitPercentage
Default - 10
Percentage of cache earmarked for asynchronous upload staging. The rest would be used for caching the downloaded files.
uploadThreads
Default - 10
The number of background threads used for asynchronous uploads.
stagingPurgeInterval
Default - 300
Interval in seconds for the background purge job to clean up uploaded entries from the upload staging cache.
stagingRetryInterval
Default - 600
Interval in seconds for the background retry job for retrying previously failed asynchronous uploads.

System properties and Framework properties

Following properties are supported by Oak. They are grouped in two parts Stable and Experimental. The stable properties would be supported in future version but the experimental properties would might not be supported in future versions

Stable

oak.mongo.uri
Type - System property and Framework Property
Specifies the MongoURI required to connect to Mongo Database
oak.mongo.db
Type - System property and Framework Property
Name of the database in Mongo

Experimental

Configuration Steps for Apache Sling

The OSGi Configuration Admin service defines a mechanism for passing configuration settings to an OSGi bundle. How a configuration is registered with the OSGi system varies depending on the application.

For example to configure DocumentNodeStore to use FileDataStore in Apache Sling

  1. Create a config file with name org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreService.cfg under ${sling.home}/install folder with content

    #Mongo server details
    mongouri=mongodb://localhost:27017
    
    #Name of Mongo database to use
    db=aem-author
    
    #Store binaries in custom BlobStore e.g. FileDataStore
    customBlobStore=true
    
  2. Create a config file with name org.apache.jackrabbit.oak.plugins.blob.datastore.FileDataStore.cfg under ${sling.home}/install folder with content

    #The minimum size of an object that should be stored in this data store.
    minRecordLength=4096
    
    #path to the DataStore
    path=./sling/repository/datastore
    
    #cache for storing small binaries in-memory
    cacheSizeInMB=128
    

Framework Properties vs OSGi Configuration

OSGi components can read config data from two sources.

  1. ConfigurationAdmin - These are configured via placing the *.cfg files under ${sling.home}/install folder. These can also be modified at runtime via Felix WebConsole typically available at http://localhost:8080/system/console
  2. Framework Properties - An OSGi framework can be configured to start with some framework properties. These properties cannot be changed at runtime. In Apache Sling these can be specified in ${sling.home}/sling.properties or ${sling.home}/conf/sling.properties

In Oak some of the config properties are also read from framework properties. If a value is specified in both config file and framework properties then framework property takes precedence.

For example by default Sling sets repository.home to ${sling.home}/repository. So this value need not be specified in config files