org.xbill.DNS
Class Cache

java.lang.Object
  org.xbill.DNS.Cache

public class Cache
extends Object

A cache of DNS records. The cache obeys TTLs, so items are purged after their validity period is complete. Negative answers are cached, to avoid repeated failed DNS queries. The credibility of each RRset is maintained, so that more credible records replace less credible records, and lookups can specify the minimum credibility of data they are requesting.

Author:

Brian Wellington

See Also:

RRset, Credibility

Constructor Summary

Cache()
Creates an empty Cache for class IN.

Cache(int dclass)
Creates an empty Cache

Cache(String file)
Creates a Cache which initially contains all records in the specified file.

Method Summary

SetResponse	addMessage(Message in) Adds all data from a Message into the Cache.
void	addNegative(Name name, int type, SOARecord soa, int cred) Adds a negative entry to the Cache.
void	addRecord(Record r, int cred, Object o) Adds a record to the Cache.
void	addRRset(RRset rrset, int cred) Adds an RRset to the Cache.
void	clearCache() Empties the Cache.
RRset[]	findAnyRecords(Name name, int type) Looks up Records in the Cache (a wrapper around lookupRecords).
RRset[]	findRecords(Name name, int type) Looks up credible Records in the Cache (a wrapper around lookupRecords).
void	flushName(Name name) Flushes all RRsets with a given name from the cache
void	flushSet(Name name, int type) Flushes an RRset from the cache
int	getDClass() Returns the DNS class of this cache.
int	getMaxCache() Gets the maximum length of time that records will be stored in this Cache.
int	getMaxEntries() Gets the maximum number of entries in the Cache, where an entry consists of all records with a specific Name.
int	getMaxNCache() Gets the maximum length of time that a negative response will be stored in this Cache.
int	getSize() Gets the current number of entries in the Cache, where an entry consists of all records with a specific Name.
protected SetResponse	lookup(Name name, int type, int minCred) Finds all matching sets or something that causes the lookup to stop.
SetResponse	lookupRecords(Name name, int type, int minCred) Looks up Records in the Cache.
void	setMaxCache(int seconds) Sets the maximum length of time that records will be stored in this Cache.
void	setMaxEntries(int entries) Sets the maximum number of entries in the Cache, where an entry consists of all records with a specific Name.
void	setMaxNCache(int seconds) Sets the maximum length of time that a negative response will be stored in this Cache.
String	toString() Returns the contents of the Cache as a string.

Methods inherited from class java.lang.Object

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

Constructor Detail

Cache

public Cache(int dclass)

Creates an empty Cache

Parameters:

dclass - The DNS class of this cache

See Also:

DClass

Cache

public Cache()

Creates an empty Cache for class IN.

See Also:

DClass

Cache

public Cache(String file)
      throws IOException

Creates a Cache which initially contains all records in the specified file.

Throws:

IOException

Method Detail

clearCache

public void clearCache()

Empties the Cache.

addRecord

public void addRecord(Record r,
                      int cred,
                      Object o)

Adds a record to the Cache.

Parameters:

r - The record to be added

cred - The credibility of the record

o - The source of the record (this could be a Message, for example)

See Also:

Record

addRRset

public void addRRset(RRset rrset,
                     int cred)

Adds an RRset to the Cache.

Parameters:

rrset - The RRset to be added

cred - The credibility of these records

See Also:

RRset

addNegative

public void addNegative(Name name,
                        int type,
                        SOARecord soa,
                        int cred)

Adds a negative entry to the Cache.

Parameters:

name - The name of the negative entry

type - The type of the negative entry

soa - The SOA record to add to the negative cache entry, or null. The negative cache ttl is derived from the SOA.

cred - The credibility of the negative entry

lookup

protected SetResponse lookup(Name name,
                             int type,
                             int minCred)

Finds all matching sets or something that causes the lookup to stop.

lookupRecords

public SetResponse lookupRecords(Name name,
                                 int type,
                                 int minCred)

Looks up Records in the Cache. This follows CNAMEs and handles negatively cached data.

Parameters:

name - The name to look up

type - The type to look up

minCred - The minimum acceptable credibility

Returns:

A SetResponse object

See Also:

SetResponse, Credibility

findRecords

public RRset[] findRecords(Name name,
                           int type)

Looks up credible Records in the Cache (a wrapper around lookupRecords). Unlike lookupRecords, this given no indication of why failure occurred.

Parameters:

name - The name to look up

type - The type to look up

Returns:

An array of RRsets, or null

See Also:

Credibility

findAnyRecords

public RRset[] findAnyRecords(Name name,
                              int type)

Looks up Records in the Cache (a wrapper around lookupRecords). Unlike lookupRecords, this given no indication of why failure occurred.

Parameters:

name - The name to look up

type - The type to look up

Returns:

An array of RRsets, or null

See Also:

Credibility

addMessage

public SetResponse addMessage(Message in)

Adds all data from a Message into the Cache. Each record is added with the appropriate credibility, and negative answers are cached as such.

Parameters:

in - The Message to be added

Returns:

A SetResponse that reflects what would be returned from a cache lookup, or null if nothing useful could be cached from the message.

See Also:

Message

flushSet

public void flushSet(Name name,
                     int type)

Flushes an RRset from the cache

Parameters:

name - The name of the records to be flushed

type - The type of the records to be flushed

See Also:

RRset

flushName

public void flushName(Name name)

Flushes all RRsets with a given name from the cache

Parameters:

name - The name of the records to be flushed

See Also:

RRset

setMaxNCache

public void setMaxNCache(int seconds)

Sets the maximum length of time that a negative response will be stored in this Cache. A negative value disables this feature (that is, sets no limit).

getMaxNCache

public int getMaxNCache()

Gets the maximum length of time that a negative response will be stored in this Cache. A negative value indicates no limit.

setMaxCache

public void setMaxCache(int seconds)

Sets the maximum length of time that records will be stored in this Cache. A negative value disables this feature (that is, sets no limit).

getMaxCache

public int getMaxCache()

Gets the maximum length of time that records will be stored in this Cache. A negative value indicates no limit.

getSize

public int getSize()

Gets the current number of entries in the Cache, where an entry consists of all records with a specific Name.

getMaxEntries

public int getMaxEntries()

Gets the maximum number of entries in the Cache, where an entry consists of all records with a specific Name. A negative value is treated as an infinite limit.

setMaxEntries

public void setMaxEntries(int entries)

Sets the maximum number of entries in the Cache, where an entry consists of all records with a specific Name. A negative value is treated as an infinite limit. Note that setting this to a value lower than the current number of entries will not cause the Cache to shrink immediately. The default maximum number of entries is 50000.

Parameters:

entries - The maximum number of entries in the Cache.

getDClass

public int getDClass()

Returns the DNS class of this cache.

toString

public String toString()

Returns the contents of the Cache as a string.

Overrides:

toString in class Object