Cache

Module	ejs
Definition	class Cache
Inheritance	Cache Object
Stability	Prototype.

Cache meta class to manage in-memory storage of key-value data.

The Cache class provides an abstraction over various in-memory and disk-based caching cache backends.

Properties

Qualifiers	Property	Type	Description
get	limits	Object	Resource limits for the server and for initial resource limits for requests.

Inherited Properties

Cache Class Methods

(No own class methods defined)

Qualifiers	Method

Inherited Methods

Cache Instance Methods

Qualifiers	Method
	Cache(adapter: String = null, options: Object = expression)
	Cache constructor.
	destroy(): Void
	Destroy the cache.
	expire(key: String, when: Date): Boolean
	Set a new expire date for a key.
	inc(key: String, amount: Number = 1): Number
	Increment a key's value by a given amount.
	read(key: String, options: Object = null): String
	Read a key.
	readObj(key: String, options: Object = null): Object
	Read a key and return an object This will read the data for a key and then deserialize.
	remove(key: String): Boolean
	Remove the key and associated value from the cache.
	setLimits(limits: Object): Void
	Update the cache cache resource limits.
	write(key: String, value: String, options: Object = null): Number
	Write the key and associated value to the cache.
	writeObj(key: String, value: Object, options: Object = null): Number
	Write the key and associated object value to the cache.

Inherited Methods

Method Detail

Cache(adapter: String = null, options: Object = expression)

Description: Cache constructor.

Parameters

adapter: String	Adapter for the cache cache. E.g. "local". The Local cache is the only currently supported cache backend. [default: null]
options: Object	Adapter options. The common options are described below, other options are passed through to the relevant caching backend. [default: expression]

Options

lifespan	Default lifespan for key values in seconds.
resolution	Time in milliseconds to check for expired expired keys.
timeout	Timeout on cache I/O operations.
trace	Trace I/O operations for debug.
module	Module name containing the cache connector class. This is a bare module name without ".mod" or any leading path. If module is not present, a module name is derrived using "ejs.cache" + adapter.
class	Class name containing the cache backend. If the class property is not present, the class is derived from the adapter name with "Cache" appended. The first letter of the adapter is converted to uppercase. For example, if the adapter was "mem", the class would be inferred to be "MemCache". H.

destroy(): Void

Description: Destroy the cache.

expire(key: String, when: Date): Boolean

Description: Set a new expire date for a key.

Parameters

key: String	Key to modify.
when: Date	Date at which to expire the data. Set to null to never expire.

Returns: True if the key's expiry can be updated.

inc(key: String, amount: Number = 1): Number

Description: Increment a key's value by a given amount. This operation is atomic.

Parameters

key: String	Key value to read.
amount: Number	Amount by which to increment the value. This amount can be negative to achieve a decrement. [default: 1]

Returns: The new key value. If the key does not exist, it is initialized to the amount value.

read(key: String, options: Object = null): String

Description: Read a key.

Parameters

key: String	Key value to read.
options: Object	Read options. [default: null]

Options

version

If set to true, the read will return an object hash containing the data and a unique version identifier for the last update to this key. This version identifier can be specified to write to peform an atomic CAS (check and swap) operation.

Returns: Null if the key is not present. Otherwise return key data as a string or if the options parameter specified "version == true", return an object with the properties "data" for the key data and "version" for the CAS version identifier.

readObj(key: String, options: Object = null): Object

Description: Read a key and return an object This will read the data for a key and then deserialize. This assumes that writeObj was used to store the key value.

Parameters

key: String	Key value to read.
options: Object	Read options. [default: null]

Options

version

Returns: Null if the key is not present. Otherwise return key data as an object. P.

remove(key: String): Boolean

Description: Remove the key and associated value from the cache.

Parameters

key: String

Key value to remove. If key is null, then all keys are removed.

Returns: True if the key was removed.

setLimits(limits: Object): Void

Description: Update the cache cache resource limits. The supplied limit fields are updated. See the limits property for limit field details.

Parameters

limits: Object

Object hash of limit fields and values.

See Also: limits

write(key: String, value: String, options: Object = null): Number

Description: Write the key and associated value to the cache. The value is written according to the optional mode option.

Parameters

key: String	Key to modify.
value: String	String value to associate with the key.
options: Object	Options values. [default: null]

Options

lifespan	Preservation time for the key in seconds.
expire	When to expire the key. Takes precedence over lifetime.
mode	Mode of writing: "set" is the default and means set a new value and create if required. "add" means set the value only if the key does not already exist. "append" means append to any existing value and create if required. "prepend" means prepend to any existing value and create if required.
version	Unique version identifier to be used for a conditional write. The write will only be performed if the version id for the key has not changed. This implements an atomic compare and swap. See read.
throw	Throw an exception rather than returning null if the version id has been updated for the key.

Returns: The number of bytes written, returns null if the write failed due to an updated version identifier for the key.

writeObj(key: String, value: Object, options: Object = null): Number

Description: Write the key and associated object value to the cache. The object value is serialized using JSON notation and written according to the optional mode option.

Parameters

key: String	Key to modify.
value: Object	Object to associate with the key.
options: Object	Options values. [default: null]

Options

lifespan	Preservation time for the key in seconds. Set to zero for never expire.
expire	When to expire the key. Takes precedence over lifetime.
mode	Mode of writing: "set" is the default and means set a new value and create if required. "add" means set the value only if the key does not already exist. "append" means append to any existing value and create if required. "prepend" means prepend to any existing value and create if required.
version	Unique version identifier to be used for a conditional write. The write will only be performed if the version id for the key has not changed. This implements an atomic compare and swap. See read.
throw	Throw an exception rather than returning null if the version id has been updated for the key.

Returns: The number of bytes written, returns null if the write failed due to an updated version identifier for the key. X.