ucar.unidata.io
Class FileCache

java.lang.Object
  ucar.unidata.io.FileCache

public class FileCache
extends java.lang.Object

Keep cache of open RandomAccessFile, for performance. Used by TDS to optimize serving netCDF files over HTTP.

  RandomAccessFile raf = null;
  try {
    RandomAccessFile raf = FileCache.acquire(location, cancelTask);
    ...
  } finally {
    FileCache.release( raf)
  }
 

Library ships with cache disabled. If you want to use, call init() and make sure you call exit() when exiting program. All methods are thread safe. Cleanup is done automatically in a background thread, using LRU.

Author:

jcaron

Nested Class Summary

static class

FileCache.CacheElement This tracks the elements in the cache.

Constructor Summary

FileCache()

Method Summary

static RandomAccessFile	acquire(java.lang.String location)
static RandomAccessFile	acquireCacheOnly(java.lang.String location) Try to find a file in the cache.
static void	clearCache(boolean force)
static void	disable() Disable use of the cache.
static void	exit() You must call exit() to shut down the background timer in order to get a clean process shutdpwn.
static java.util.List	getCache() Get the files in the cache.
static void	init() Default 10 minimum, 20 maximum files, cleanup every 20 minutes
static void	init(int minElementsInMemory, int maxElementsInMemory, long period) Initialize the cache.
static void	release(RandomAccessFile raf) Release the file.

Methods inherited from class java.lang.Object

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

Constructor Detail

FileCache

public FileCache()

Method Detail

init

public static void init()

Default 10 minimum, 20 maximum files, cleanup every 20 minutes

init

public static void init(int minElementsInMemory,
                        int maxElementsInMemory,
                        long period)

Initialize the cache. If you dont, default values will be used. Call disable if you dont want caching.

Parameters:

minElementsInMemory - keep this number in the cache

maxElementsInMemory - trigger a cleanup if it goes over this number.

period - (secs) do periodic cleanups every this number of seconds.

disable

public static void disable()

Disable use of the cache. Call init() to start again. Generally call this before any possible use.

exit

public static void exit()

You must call exit() to shut down the background timer in order to get a clean process shutdpwn.

acquireCacheOnly

public static RandomAccessFile acquireCacheOnly(java.lang.String location)

Try to find a file in the cache.

Parameters:

location - file location is used as the key.

Returns:

file if its in the cache, null otherwise.

acquire

public static RandomAccessFile acquire(java.lang.String location)
                                throws java.io.IOException

Throws:

java.io.IOException

release

public static void release(RandomAccessFile raf)
                    throws java.io.IOException

Release the file. This unlocks it, updates its lastAccessed date.

Parameters:

raf - release this file.

Throws:

java.io.IOException - if file not in cache.

getCache

public static java.util.List getCache()

Get the files in the cache. For debugging/status only, do not change!

Returns:

List of FileCache.CacheElement

clearCache

public static void clearCache(boolean force)