Naanou.ResourceExchange
Class BlockStorage

Manages the partial uncomplete download blocks

blocks

private System.Collections.ArrayList blocks

Blocks that have been finished and are stored

diskUsageKB

private long diskUsageKB

Total disk usage

gcDue

private bool gcDue

inited

private bool inited

inUseBlocks

private System.Collections.ArrayList inUseBlocks

Blocks that are currently being written too

rwl

private System.Threading.ReaderWriterLock rwl

BlockStorage

public BlockStorage()

Initializes a new instance of the BlockStorage class.

DiskUsage

internal long DiskUsage

Gets the disk usage (in KB) of blocks

GcDue

public bool GcDue

Gets whether a GC is due

Oversize

internal bool Oversize

Is storage oversize?

Utilisation

internal double Utilisation

Gets utilisation of block storage

UtilStats

internal string UtilStats

Gets a short string indicating utilisation details

Create

internal Naanou.ResourceExchange.Block Create(long start,
                                              long end,
                                              long length,
                                              string contentHash)

Creates a new block for a resource

Parameters:

contentHash - Hash of contents

end - Ending byte number (0-based)

length - Total length of resource

start - Starting byte number (0-based)

Returns:

New block

DecrementDiskUsage

private void DecrementDiskUsage(long amountKb)

Decrements the disk usage counter

Parameters:

amountKb - Amount in kilobytes to decrement by

Delete

internal void Delete(Naanou.ResourceExchange.Block block)

Deletes a block from disk and internal db

Parameters:

block - Block to delete

Throws:

System.ArgumentException - If block is marked Naanou.ResourceExchange.Block.RequiredLocally

Delete

internal void Delete(Naanou.ResourceExchange.Block block,
                     bool force)

Deletes a block from memory and disk

Parameters:

block - Block to delete

force - If true, block will be removed even if block's RequiredLocally flag is set

DeleteFile

private void DeleteFile(System.IO.FileInfo file)

Deletes a file from disk

Parameters:

file -

Gc

public void Gc(bool startupGc)

Garbage collect block storage

Uses four methods to clean up on disk and memory usage. The fourth method is only performed when the first three fail to clean up enough space. Method - Description

1. Disk orphans - Finds blocks stored on disk that are no longer being kept track of (i.e. not in memory)

2. Memory orphans - Finds blocks that we are keeping track of in memory that no longer have a data on disk

3. Stale - Finds blocks on disk that are stale. Stale blocks are ones that are incomplete, and haven't been written to for a while (based on Naanou.ResourceExchange.Config.BlockStorageTimeout)

4. LRU - Deletes blocks in Least Recently Used order until enough space is cleared

GcDiskOrphans

private long GcDiskOrphans(Naanou.Common.PriorityQueue list,
                           bool startupGc)

Find blocks on disk that we don't know about. If startupGc is true, will also delete any incomplete blocks found

Parameters:

list - Returns a priority queue of blocks sorted in order of last write

startupGc - Is Gc running due to a program startup?

Returns:

Disk usage of blocks in KB

GcMemoryOrphans

private void GcMemoryOrphans(bool startupGc)

Remove all orphans in memory.

GcStale

private void GcStale(Naanou.Common.PriorityQueue pq)

Goes thru the sorted list {tick => block} and deletes blocks that are too old and incomplete

Parameters:

pq - Priority queue in last write ticks order

GcUnpopular

private void GcUnpopular()

Sorts blocks by accessed frequency, and removes least accessed blocks first

GetBlockFilename

private string GetBlockFilename(string contentHash,
                                string range)

Gets the absolute filename for a block

Parameters:

contentHash - Hash

range - Range

Returns:

Filename

IncrementDiskUsage

private void IncrementDiskUsage(long amountKb)

Increments the disk usage counter

Parameters:

amountKb - Amount in kilobytes to increment by

Init

internal void Init()

Load

internal void Load()

Loads block info from disk, forgetting current state. This is called on program startup

PromoteBlock

internal void PromoteBlock(Naanou.ResourceExchange.Block block)

Promotes a block from `in use' to idle. Do not call this method directly, use Naanou.ResourceExchange.Block.Retire.

Parameters:

block -

Query

internal Naanou.ResourceExchange.Block[] Query(string contentHash)

Find all complete blocks that are part of a certain file

Parameters:

contentHash - Contents hash

Returns:

Matching blocks

Query

private long Query(string contentHash,
                   System.Collections.ArrayList output,
                   System.Collections.ArrayList source)

QueryAny

internal Naanou.ResourceExchange.Block[] QueryAny(string contentHash)

Finds all blocks complete or not

Parameters:

contentHash - Hash

Save

internal void Save()

Saves current block info to disk