Package netscape.ldap

Class LDAPCache

java.lang.Object
netscape.ldap.LDAPCache
All Implemented Interfaces:
Serializable
public class LDAPCache extends Object implements Serializable
LDAPCache represents an in-memory cache that you can use to reduce the number of search requests sent to the LDAP server.

Each item in the cache represents a search request and its results. Each item is uniquely identified by the search criteria, which includes:

  • the host name and port number of the LDAP server
  • the base DN of the search
  • the search filter
  • the scope of the search
  • the attributes to be returned in the search results
  • the DN used to authenticate the client when binding to the server
  • the LDAP v3 controls specified in the search request

After a search request is cached, the results of any subsequent search requests using the same criteria are read from the cache. Note that if any part of the criteria differs (for example, if a different DN is used when binding to the server or if a different set of attributes to be returned is specified), the search request is sent to the server.

When you create the cache, you specify the maximum amount of time that an item can be kept in the cache. When an item's age exceeds that time limit, the item is removed from the cache.

The cache also has a maximum size that you specify when creating the cache. If adding a new item exceeds the maximum size of the cache, the first entries in the cache are removed to make enough space for the new item.

Finally, when creating the cache, you can specify a list of the base DNs in search requests that you want to cache. For example, if you specify o=Airius.com as a base DN to cache, your client caches search requests where the base DN is o=Airius.com.

To specify that you want to use a cache for a particular LDAP session, call the setCache method of the LDAPConnection object that you are working with.

All clones of an LDAPConnection object share the same LDAPCache object.

Note that LDAPCache does not maintain consistency with the directory, so that cached search results may no longer be valid after a directory update. If the same application is performing both cached searches and directory updates, then the application should flush the corresponding cache entries after an update. To do this use the flushEntries method.

Also, note that search requests that return referrals are not cached.

The LDAPCache class includes methods for getting statistics (such as hit rates) from the cache and for flushing entries from the cache.

See Also:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final String
    DELIM
    Delimiter used internally when creating keys for the cache.
    private Hashtable<Long,Vector<Object>>
    m_cache
    A hashtable of search results.
    private static boolean
    m_debug
     
    private String[]
    m_dns
     
    private long
    m_flushes
     
    private long
    m_hits
     
    private long
    m_maxSize
     
    private Vector<Vector<Long>>
    m_orderedStruct
    A list of cached entries ordered by time (augments m_cache).
    private int
    m_refCnt
     
    private long
    m_remainingSize
     
    private TTLTimer
    m_timer
     
    private long
    m_timeToLive
     
    private long
    m_totalOpers
     
    (package private) static final long
    serialVersionUID
     

  • Constructor Summary

    Constructors
    Constructor
    Description
    LDAPCache(long ttl, long size)
    Constructs a new LDAPCache object, using the specified maximum size of the cache (in bytes) and the maximum age of cached items (in seconds).
    LDAPCache(long ttl, long size, String[] dns)
    Constructs a new LDAPCache object, using the specified maximum size of the cache (in bytes), and the maximum age of cached items (in seconds), and an array of the base DNs of searches that you want to cache.

  • Method Summary

    Modifier and Type
    Method
    Description
    (package private) boolean
    addEntry(Long key, Object value)
    Add the entry to the hashtable cache and to the vector respectively.
    (package private) void
    addReference()
    Add a new reference to this cache.
    private String
    appendString(int num)
    Concatenates the specified integer with the delimiter.
    private String
    appendString(String str)
    Concatenates the specified integer with the delimiter.
    private String
    appendString(String[] str)
    Concatenate the specified string array with the delimiter.
    (package private) void
    cleanup()
    Cleans up
    (package private) Long
    createKey(String host, int port, String baseDN, String filter, int scope, String[] attrs, String bindDN, LDAPConstraints cons)
    Create a key for a cache entry by concatenating all input parameters
    (package private) void
    flushEntries()
    Flush entries which stay longer or equal to the time-to-live.
    boolean
    flushEntries(String dn, int scope)
    Flush the entries identified by DN and scope from the cache.
    long
    getAvailableSize()
    Gets the amount of available space (in bytes) left in the cache.
    String[]
    getBaseDNs()
    Gets the array of base DNs of searches to be cached.
    private long
    getCRC32(byte[] barray)
    Create a 32 bits CRC from the given byte array.
    (package private) Object
    getEntry(Long key)
    Gets the cache entry based on the specified key.
    int
    getNumEntries()
    Gets the number of entries being cached.
    long
    getNumFlushes()
    Gets the total number of entries that are flushed when timer expires and flushEntries is called.
    long
    getNumHits()
    Gets the total number of requests which successfully found and retrieved an item from the cache.
    long
    getNumMisses()
    Gets the total number of requests which failed to find and retrieve an item from the cache.
    (package private) int
    getRefCount()
    Get number of LDAPConnections that share this cache
    long
    getSize()
    Gets the maximum size of the cache (in bytes).
    long
    getTimeToLive()
    Gets the maximum age allowed for cached items (in seconds).
    long
    getTotalOperations()
    Gets the total number of requests for retrieving items from the cache.
    private void
    init(long ttl, long size)
    Initialize the instance variables.
    (package private) void
    removeReference()
    Remove a reference to this cache.
    (package private) void
    scheduleTTLTimer()
    Flush entries which stayed longer or equal to the time-to-live, and Set up the TTLTimer for the next flush.
    private void
    sortStrings(String[] str)
    Sorts the array of strings using bubble sort.

    Methods inherited from class java.lang.Object

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

  • Field Details

    • serialVersionUID

      static final long serialVersionUID
      See Also:

    • m_cache

      private Hashtable<Long,Vector<Object>> m_cache
      A hashtable of search results. The key is created from the search request parameters (see createKey() method). The value is a Vector where the first element is a Long integer representing the size of all entries, followed by the actual search result entries (of type LDAPEntry).

    • m_orderedStruct

      private Vector<Vector<Long>> m_orderedStruct
      A list of cached entries ordered by time (augments m_cache). Each element in the list is a 2 element Vector where the element at index 0 is the key in the m_cache table, and the element at index 1 is the time when the entry was created. The list is used to track the time-to-live limit and to implement the FIFO algorithm when adding new entries; if the size of the new entry exceeds the cache available space, the extra space is made by removing existing cached results in the order of their entry in the cache.

    • m_timeToLive

      private long m_timeToLive

    • m_maxSize

      private long m_maxSize

    • m_dns

      private String[] m_dns

    • m_remainingSize

      private long m_remainingSize

    • m_refCnt

      private int m_refCnt

    • DELIM

      public static final String DELIM
      Delimiter used internally when creating keys for the cache.
      See Also:

    • m_timer

      private TTLTimer m_timer

    • m_totalOpers

      private long m_totalOpers

    • m_hits

      private long m_hits

    • m_flushes

      private long m_flushes

    • m_debug

      private static boolean m_debug

  • Constructor Details

    • LDAPCache

      public LDAPCache(long ttl, long size)
      Constructs a new LDAPCache object, using the specified maximum size of the cache (in bytes) and the maximum age of cached items (in seconds). When items in the cache exceed this age, they are removed from the cache.

      Parameters:
      ttl - the maximum amount of time that an item can be cached (in seconds)
      size - the maximum size of the cache (in bytes)

    • LDAPCache

      public LDAPCache(long ttl, long size, String[] dns)
      Constructs a new LDAPCache object, using the specified maximum size of the cache (in bytes), and the maximum age of cached items (in seconds), and an array of the base DNs of searches that you want to cache. (For example, if the array of base DNs includes o=Airius.com, the cache stores search results if the base DN in the search request is o=Airius.com.)

      Parameters:
      ttl - the maximum amount of time that an item can be cached (in seconds)
      size - the maximum size of the cache (in bytes)
      dns - the list of base DNs of searches that you want to cache.

  • Method Details

    • getSize

      public long getSize()
      Gets the maximum size of the cache (in bytes).

      Returns:
      the maximum size of the cache (in bytes).

    • getTimeToLive

      public long getTimeToLive()
      Gets the maximum age allowed for cached items (in seconds). (Items that exceed this age are removed from the cache.)

      Returns:
      the maximum age of items in the cache (in seconds).

    • getBaseDNs

      public String[] getBaseDNs()
      Gets the array of base DNs of searches to be cached. (Search requests with these base DNs are cached.)

      Returns:
      the array of base DNs.

    • flushEntries

      public boolean flushEntries(String dn, int scope)
      Flush the entries identified by DN and scope from the cache.

      Parameters:
      dn - the distinguished name (or base DN) of the entries to be removed from the cache. Use this parameter in conjunction with scope to identify the entries that you want removed from the cache. If this parameter is null, the entire cache is flushed.
      scope - the scope identifying the entries that you want removed from the cache. The value of this parameter can be one of the following:
      • LDAPv2.SCOPE_BASE (to remove the entry identified by dn)
      • LDAPv2.SCOPE_ONE (to remove the entries that have dn as their parent entry)
      • LDAPv2.SCOPE_SUB (to remove the entries in the subtree under dn in the directory)

      Returns:
      true if the entry is removed from the cache; false if the entry is not removed.

    • getAvailableSize

      public long getAvailableSize()
      Gets the amount of available space (in bytes) left in the cache.

      Returns:
      the available space (in bytes) in the cache.

    • getTotalOperations

      public long getTotalOperations()
      Gets the total number of requests for retrieving items from the cache. This includes both items successfully found in the cache and items not found in the cache.

      Returns:
      the total number of requests for retrieving items from the cache.

    • getNumMisses

      public long getNumMisses()
      Gets the total number of requests which failed to find and retrieve an item from the cache.

      Returns:
      the number of requests that did not find and retrieve an item in the cache.

    • getNumHits

      public long getNumHits()
      Gets the total number of requests which successfully found and retrieved an item from the cache.
      Returns:
      the number of requests that successfully found and retrieved an item from the cache.

    • getNumFlushes

      public long getNumFlushes()
      Gets the total number of entries that are flushed when timer expires and flushEntries is called.

      Returns:
      the total number of entries that are flushed when timer expires.

    • createKey

      Long createKey(String host, int port, String baseDN, String filter, int scope, String[] attrs, String bindDN, LDAPConstraints cons) throws LDAPException
      Create a key for a cache entry by concatenating all input parameters
      Returns:
      the key for a cache entry
      Throws:
      LDAPException - Thrown when failed to create key.

    • getEntry

      Object getEntry(Long key)
      Gets the cache entry based on the specified key.
      Parameters:
      key - the key for the cache entry
      Returns:
      the cache entry.

    • flushEntries

      void flushEntries()
      Flush entries which stay longer or equal to the time-to-live.

    • addEntry

      boolean addEntry(Long key, Object value)
      Add the entry to the hashtable cache and to the vector respectively. The vector is used to keep track of the order of the entries being added.
      Parameters:
      key - the key for the cache entry
      value - the cache entry being added to the cache for the specified key
      Returns:
      a flag indicating whether the entry was added.

    • scheduleTTLTimer

      void scheduleTTLTimer()
      Flush entries which stayed longer or equal to the time-to-live, and Set up the TTLTimer for the next flush. Called when first entry is added to the cache and when the TTLTimer expires.

    • getNumEntries

      public int getNumEntries()
      Gets the number of entries being cached.
      Returns:
      the number of entries being cached.

    • getRefCount

      int getRefCount()
      Get number of LDAPConnections that share this cache
      Returns:
      Reference Count

    • addReference

      void addReference()
      Add a new reference to this cache.

    • removeReference

      void removeReference()
      Remove a reference to this cache. If the reference count is 0, cleaup the cache.

    • cleanup

      void cleanup()
      Cleans up

    • init

      private void init(long ttl, long size)
      Initialize the instance variables.

    • appendString

      private String appendString(String str)
      Concatenates the specified integer with the delimiter.
      Parameters:
      str - the String to concatenate with the delimiter
      Returns:
      the concatenated string.

    • appendString

      private String appendString(int num)
      Concatenates the specified integer with the delimiter.
      Parameters:
      num - the integer to concatenate with the delimiter
      Returns:
      the concatenated string.

    • appendString

      private String appendString(String[] str)
      Concatenate the specified string array with the delimiter.
      Parameters:
      str - a string array
      Returns:
      the concatenated string.

    • sortStrings

      private void sortStrings(String[] str)
      Sorts the array of strings using bubble sort.
      Parameters:
      str - the array of strings to sort. The str parameter contains the sorted result.

    • getCRC32

      private long getCRC32(byte[] barray)
      Create a 32 bits CRC from the given byte array.