io.pravega.storage.filesystem

Class FileSystemStorage

java.lang.Object

io.pravega.storage.filesystem.FileSystemStorage

All Implemented Interfaces:

io.pravega.segmentstore.storage.SyncStorage, java.lang.AutoCloseable

public class FileSystemStorage
extends java.lang.Object
implements io.pravega.segmentstore.storage.SyncStorage

Storage adapter for file system based storage. Each segment is represented as a single file on the underlying storage. Approach to fencing: This implementation works under the assumption that data is only appended and never modified. Each block of data has an offset assigned to it and Pravega always writes the same data to the same offset. With this assumption the only flow when a write call is made to the same offset twice is when ownership of the segment changes from one host to another and both the hosts are writing to it. As write to same offset to a file is idempotent (any attempt to re-write data with the same file offset does not cause any form of inconsistency), locking is not required. In the absence of locking this is the expected behavior in case of ownership change: both the hosts will keep writing the same data at the same offset till the time the earlier owner gets a notification that it is not the current owner. Once the earlier owner received this notification, it stops writing to the segment.

Constructor Summary

Constructors

Constructor and Description
FileSystemStorage(FileSystemStorageConfig config) Creates a new instance of the FileSystemStorage class.

Method Summary

Modifier and Type	Method and Description
void	close()
void	concat(io.pravega.segmentstore.storage.SegmentHandle targetHandle, long offset, java.lang.String sourceSegment)
io.pravega.segmentstore.storage.SegmentHandle	create(java.lang.String streamSegmentName)
void	delete(io.pravega.segmentstore.storage.SegmentHandle handle)
boolean	exists(java.lang.String streamSegmentName)
io.pravega.segmentstore.contracts.SegmentProperties	getStreamSegmentInfo(java.lang.String streamSegmentName)
void	initialize(long containerEpoch) Initialize is a no op here as we do not need a locking mechanism in case of file system write.
io.pravega.segmentstore.storage.SegmentHandle	openRead(java.lang.String streamSegmentName)
io.pravega.segmentstore.storage.SegmentHandle	openWrite(java.lang.String streamSegmentName)
int	read(io.pravega.segmentstore.storage.SegmentHandle handle, long offset, byte[] buffer, int bufferOffset, int length)
void	seal(io.pravega.segmentstore.storage.SegmentHandle handle)
boolean	supportsTruncation()
void	truncate(io.pravega.segmentstore.storage.SegmentHandle handle, long offset)
void	unseal(io.pravega.segmentstore.storage.SegmentHandle handle)
void	write(io.pravega.segmentstore.storage.SegmentHandle handle, long offset, java.io.InputStream data, int length)

Methods inherited from class java.lang.Object

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

Methods inherited from interface io.pravega.segmentstore.storage.SyncStorage

create

Constructor Detail

FileSystemStorage

public FileSystemStorage(FileSystemStorageConfig config)

Creates a new instance of the FileSystemStorage class.

Parameters:

config - The configuration to use.

Method Detail

initialize

public void initialize(long containerEpoch)

Initialize is a no op here as we do not need a locking mechanism in case of file system write.

Specified by:

initialize in interface io.pravega.segmentstore.storage.SyncStorage

Parameters:

containerEpoch - The Container Epoch to initialize with (ignored here).

openRead

public io.pravega.segmentstore.storage.SegmentHandle openRead(java.lang.String streamSegmentName)
                                                       throws io.pravega.segmentstore.contracts.StreamSegmentException

Specified by:

openRead in interface io.pravega.segmentstore.storage.SyncStorage

Throws:

io.pravega.segmentstore.contracts.StreamSegmentException

read

public int read(io.pravega.segmentstore.storage.SegmentHandle handle,
                long offset,
                byte[] buffer,
                int bufferOffset,
                int length)
         throws io.pravega.segmentstore.contracts.StreamSegmentException

Specified by:

read in interface io.pravega.segmentstore.storage.SyncStorage

Throws:

io.pravega.segmentstore.contracts.StreamSegmentException

getStreamSegmentInfo

public io.pravega.segmentstore.contracts.SegmentProperties getStreamSegmentInfo(java.lang.String streamSegmentName)
                                                                         throws io.pravega.segmentstore.contracts.StreamSegmentException

Specified by:

getStreamSegmentInfo in interface io.pravega.segmentstore.storage.SyncStorage

Throws:

io.pravega.segmentstore.contracts.StreamSegmentException

exists

public boolean exists(java.lang.String streamSegmentName)

Specified by:

exists in interface io.pravega.segmentstore.storage.SyncStorage

openWrite

public io.pravega.segmentstore.storage.SegmentHandle openWrite(java.lang.String streamSegmentName)
                                                        throws io.pravega.segmentstore.contracts.StreamSegmentException

Specified by:

openWrite in interface io.pravega.segmentstore.storage.SyncStorage

Throws:

io.pravega.segmentstore.contracts.StreamSegmentException

create

public io.pravega.segmentstore.storage.SegmentHandle create(java.lang.String streamSegmentName)
                                                     throws io.pravega.segmentstore.contracts.StreamSegmentException

Specified by:

create in interface io.pravega.segmentstore.storage.SyncStorage

Throws:

io.pravega.segmentstore.contracts.StreamSegmentException

write

public void write(io.pravega.segmentstore.storage.SegmentHandle handle,
                  long offset,
                  java.io.InputStream data,
                  int length)
           throws io.pravega.segmentstore.contracts.StreamSegmentException

Specified by:

write in interface io.pravega.segmentstore.storage.SyncStorage

Throws:

io.pravega.segmentstore.contracts.StreamSegmentException

seal

public void seal(io.pravega.segmentstore.storage.SegmentHandle handle)
          throws io.pravega.segmentstore.contracts.StreamSegmentException

Specified by:

seal in interface io.pravega.segmentstore.storage.SyncStorage

Throws:

io.pravega.segmentstore.contracts.StreamSegmentException

unseal

public void unseal(io.pravega.segmentstore.storage.SegmentHandle handle)
            throws io.pravega.segmentstore.contracts.StreamSegmentException

Specified by:

unseal in interface io.pravega.segmentstore.storage.SyncStorage

Throws:

io.pravega.segmentstore.contracts.StreamSegmentException

concat

public void concat(io.pravega.segmentstore.storage.SegmentHandle targetHandle,
                   long offset,
                   java.lang.String sourceSegment)
            throws io.pravega.segmentstore.contracts.StreamSegmentException

Specified by:

concat in interface io.pravega.segmentstore.storage.SyncStorage

Throws:

io.pravega.segmentstore.contracts.StreamSegmentException

delete

public void delete(io.pravega.segmentstore.storage.SegmentHandle handle)
            throws io.pravega.segmentstore.contracts.StreamSegmentException

Specified by:

delete in interface io.pravega.segmentstore.storage.SyncStorage

Throws:

io.pravega.segmentstore.contracts.StreamSegmentException

truncate

public void truncate(io.pravega.segmentstore.storage.SegmentHandle handle,
                     long offset)

Specified by:

truncate in interface io.pravega.segmentstore.storage.SyncStorage

supportsTruncation

public boolean supportsTruncation()

Specified by:

supportsTruncation in interface io.pravega.segmentstore.storage.SyncStorage

close

public void close()

Specified by:

close in interface io.pravega.segmentstore.storage.SyncStorage

Specified by:

close in interface java.lang.AutoCloseable