Storage (Copycat API Reference (1.1.4))

java.lang.Object
- io.atomix.copycat.server.storage.Storage

```
public class Storage
extends Object
```
Immutable log configuration and Log factory.
This class provides a factory for Log objects. Storage objects are immutable and can be created only via the Storage.Builder. To create a new Storage.Builder, use the static builder() factory method:
```
   
     Storage storage = Storage.builder()
       .withDirectory(new File("logs"))
       .withStorageLevel(StorageLevel.DISK)
       .build();
   
 
```
Users can also configure a number of options related to how logs are constructed and managed. Most notable of the configuration options is the number of compactionThreads(), which specifies the number of background threads to use to compact log segments. The parallelism of the log compaction algorithm will be limited by the number of compactionThreads().
Author:

See Also:
Log

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class Storage.Builder
Builds a Storage configuration.

Nested Classes
Modifier and Type	Class and Description
`static class`	`Storage.Builder` Builds a `Storage` configuration.

Constructor Summary

Constructors
Constructor and Description
`Storage()`
`Storage(File directory)`
`Storage(File directory, StorageLevel storageLevel)`
`Storage(StorageLevel storageLevel)`
`Storage(String directory)`
`Storage(String directory, StorageLevel storageLevel)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`static Storage.Builder`	`builder()` Returns a new storage builder.
`int`	`compactionThreads()` Returns the number of log compaction threads.
`double`	`compactionThreshold()` Returns the compaction threshold.
`void`	`deleteLog(String name)` Deletes a `Log` from disk.
`void`	`deleteMetaStore(String name)` Deletes a `MetaStore` from disk.
`void`	`deleteSnapshotStore(String name)` Deletes a `SnapshotStore` from disk.
`File`	`directory()` Returns the storage directory.
`int`	`entryBufferSize()` Returns the entry buffer size.
`boolean`	`flushOnCommit()` Returns whether to flush buffers to disk when entries are committed.
`StorageLevel`	`level()` Returns the storage level.
`Duration`	`majorCompactionInterval()` Returns the major compaction interval.
`int`	`maxEntriesPerSegment()` Returns the maximum number of entries per segment.
`int`	`maxSegmentSize()` Returns the maximum log segment size.
`Duration`	`minorCompactionInterval()` Returns the minor compaction interval.
`Log`	`openLog(String name)` Opens a new `Log`, recovering the log from disk if it exists.
`MetaStore`	`openMetaStore(String name)` Opens a new `MetaStore`, recovering metadata from disk if it exists.
`SnapshotStore`	`openSnapshotStore(String name)` Opens a new `SnapshotStore`, recovering snapshots from disk if they exist.
`boolean`	`retainStaleSnapshots()` Returns a boolean value indicating whether to retain stale snapshots on disk.
`String`	`toString()`

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - Storage
```
public Storage()
```
  - Storage
```
public Storage(StorageLevel storageLevel)
```
  - Storage
```
public Storage(String directory)
```
    Throws:
    
    NullPointerException - if directory is null
  - Storage
```
public Storage(File directory)
```
    Throws:
    
    NullPointerException - if directory is null
  - Storage
```
public Storage(String directory,
               StorageLevel storageLevel)
```
    Throws:
    
    NullPointerException - if directory is null
  - Storage
```
public Storage(File directory,
               StorageLevel storageLevel)
```
    Throws:
    
    NullPointerException - if directory is null
- Method Detail
  - builder
```
public static Storage.Builder builder()
```
    Returns a new storage builder.
    
    Returns:
    
    A new storage builder.
  - directory
```
public File directory()
```
    Returns the storage directory.
    The storage directory is the directory to which all Logs write Segment files. Segment files for multiple logs may be stored in the storage directory, and files for each log instance will be identified by the name provided when the log is opened.
    
    Returns:
    
    The storage directory.
  - level
```
public StorageLevel level()
```
    Returns the storage level.
    The storage level dictates how entries within individual log Segments should be stored.
    
    Returns:
    
    The storage level.
  - maxSegmentSize
```
public int maxSegmentSize()
```
    Returns the maximum log segment size.
    The maximum segment size dictates the maximum size any Segment in a Log may consume in bytes.
    
    Returns:
    
    The maximum segment size in bytes.
  - maxEntriesPerSegment
```
public int maxEntriesPerSegment()
```
    Returns the maximum number of entries per segment.
    The maximum entries per segment dictates the maximum number of entries that are allowed to be stored in any Segment in a Log.
    
    Returns:
    
    The maximum number of entries per segment.
  - entryBufferSize
```
public int entryBufferSize()
```
    Returns the entry buffer size.
    The entry buffer size dictates the number of entries that will be held in memory for read operations at the tail of the log.
    
    Returns:
    
    The entry buffer size.
  - flushOnCommit
```
public boolean flushOnCommit()
```
    Returns whether to flush buffers to disk when entries are committed.
    
    Returns:
    
    Whether to flush buffers to disk when entries are committed.
  - retainStaleSnapshots
```
public boolean retainStaleSnapshots()
```
    Returns a boolean value indicating whether to retain stale snapshots on disk.
    If this option is enabled, snapshots will be retained on disk even after they no longer contribute to the state of the system (there's a more recent snapshot). Users may want to disable this option for backup purposes.
    
    Returns:
    
    Indicates whether to retain stale snapshots on disk.
  - compactionThreads
```
public int compactionThreads()
```
    Returns the number of log compaction threads.
    The compaction thread count dictates the parallelism with which the log Compactor can rewrite segments in the log.
    
    Returns:
    
    The number of log compaction threads.
  - minorCompactionInterval
```
public Duration minorCompactionInterval()
```
    Returns the minor compaction interval.
    The minor compaction interval dictates the interval at which the MinorCompactionManager should evaluate Segments in the log for minor compaction.
    
    Returns:
    
    The minor compaction interval.
  - majorCompactionInterval
```
public Duration majorCompactionInterval()
```
    Returns the major compaction interval.
    The major compaction interval dictates the interval at which the MajorCompactionManager should evaluate Segments in the log for major compaction.
    
    Returns:
    
    The major compaction interval.
  - compactionThreshold
```
public double compactionThreshold()
```
    Returns the compaction threshold.
    The compaction threshold is used during minor compaction to determine the set of segments to compact.
    
    Returns:
    
    The compaction threshold.
  - openMetaStore
```
public MetaStore openMetaStore(String name)
```
    Opens a new MetaStore, recovering metadata from disk if it exists.
    The meta store will be loaded using based on the configured StorageLevel. If the storage level is persistent then the meta store will be loaded from disk, otherwise a new meta store will be created.
    
    Parameters:
    
    name - The metastore name.
    
    Returns:
    
    The metastore.
  - deleteMetaStore
```
public void deleteMetaStore(String name)
```
    Deletes a MetaStore from disk.
    The meta store will be deleted by simply reading meta file names from disk and deleting metadata files directly. Deleting the meta store does not involve reading any metadata files into memory.
    
    Parameters:
    
    name - The metastore name.
  - openSnapshotStore
```
public SnapshotStore openSnapshotStore(String name)
```
    Opens a new SnapshotStore, recovering snapshots from disk if they exist.
    The snapshot store will be loaded using based on the configured StorageLevel. If the storage level is persistent then the snapshot store will be loaded from disk, otherwise a new snapshot store will be created.
    
    Parameters:
    
    name - The snapshot store name.
    
    Returns:
    
    The snapshot store.
  - deleteSnapshotStore
```
public void deleteSnapshotStore(String name)
```
    Deletes a SnapshotStore from disk.
    The snapshot store will be deleted by simply reading snapshot file names from disk and deleting snapshot files directly. Deleting the snapshot store does not involve reading any snapshot files into memory.
    
    Parameters:
    
    name - The snapshot store name.
  - openLog
```
public Log openLog(String name)
```
    Opens a new Log, recovering the log from disk if it exists.
    When a log is opened, the log will attempt to load Segments from the storage directory() according to the provided log name. If segments for the given log name are present on disk, segments will be loaded and indexes will be rebuilt from disk. If no segments are found, an empty log will be created.
    When log files are loaded from disk, the file names are expected to be based on the provided log name.
    
    Parameters:
    
    name - The log name.
    
    Returns:
    
    The opened log.
  - deleteLog
```
public void deleteLog(String name)
```
    Deletes a Log from disk.
    The log will be deleted by simply reading log file names from disk and deleting log files directly. Deleting log files does not involve rebuilding indexes or reading any logs into memory.
    
    Parameters:
    
    name - The log name.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class Storage

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Storage

Storage

Storage

Storage

Storage

Storage

Method Detail

builder

directory

level

maxSegmentSize

maxEntriesPerSegment

entryBufferSize

flushOnCommit

retainStaleSnapshots

compactionThreads

minorCompactionInterval

majorCompactionInterval

compactionThreshold

openMetaStore

deleteMetaStore

openSnapshotStore

deleteSnapshotStore

openLog

deleteLog

toString