A cache plugin for cache-service.
npm install cache-service-cache-module* A light-weight cache plugin for superagent-cache and cache-service
* AND a standalone in-memory cache that's optionally backed by localStorage and sessionStorage
#### Features
* Optionally backed by localStorage and sessionStorage
* Background refresh
* No external dependencies
* Robust API
* Built-in logging with a verbose flag.
* Compatible with cache-service and superagent-cache
* Excellent .mset() implementation which allows you to set expirations on a per key, per function call, and/or per cache-service-cache-module instance basis.
Require and instantiate
``javascript
var cModule = require('cache-service-cache-module');
var cacheModuleConfig = {storage: 'session', defaultExpiration: 60};
var cacheModule = new cModule(cacheModuleConfig);
`
Cache!
`javascript`
cacheModule.set('key', 'value');
cache-service-cache-module's constructor takes an optional config object with any number of the following properties:
An arbitrary identifier you can assign so you know which cache is responsible for logs and errors. IMPORTANT If you use more than one instance of cache-service-cache-module at a time and persist to browser storage from both of them, you must set this to a unique value. If you do not, your cache instances will overwrite each other when persisting to browser storage.
* type: string
* default: 'cache-module'
Indicates whether cacheModule's in-memory cache should be backed by localStorage or sessionStorage. The available options are 'local' and 'session'. If not set, or if running in node, it will default to an in-memory cache. When a browser storage is activated, cacheModule will still write to and read from an in-memory cache in the interest of speed, but at initialization it will load it's in-memory cache from browser storage and write all changes back to browser storage.
* type: string
* default: ''
The expiration to include when executing cache set commands. Can be overridden via .set()'s optional expiraiton param.
* type: int
* default: 900
* measure: seconds
How frequently should all background refresh-enabled keys be scanned to determine whether they should be refreshed. For a more thorough explanation on background refresh, see the Using Background Refresh section.
* type: int
* default: 60000
* measure: milliseconds
The maximum ttl a scanned background refresh-enabled key can have without triggering a refresh. This number should always be greater than backgroundRefreshInterval.
* type: int
* default: 70000
* measure: milliseconds
Whether to throw an exception if backgroundRefreshInterval is greater than backgroundRefreshMinTtl. Setting this property to false is highly discouraged.
* type: boolean
* default: true
> When used with cache-service, this property is overridden by cache-service's verbose value.
When false, cache-service-cache-module will log only errors. When true, cache-service-cache-module will log all activity (useful for testing and debugging).
* type: boolean
* default: false
Whether a cache should not be written to. Useful if you're sharing a redis cache with another team and your contract with them is that you will not alter their data.
* type: boolean
* default: false
As a cache-service-compatible cache, cache-service-cache-module matches cache-service's API.
Retrieve a value by a given key.
* key: type: string
* callback: type: function
* err: type: object
* response: type: string or object
Retrieve the values belonging to a series of keys. If a key is not found, it will not be in response.
* keys: type: an array of strings
* callback: type: function
* err: type: object
* response: type: object, example: {key: 'value', key2: 'value2'...}
> See the Using Background Refresh section for more about the refresh and callback params.
Set a value by a given key.
* key: type: string
* value: type: string || objects
* expiration: type: int, measure: seconds
* refresh: type: function
* callback: type: function
Set multiple values to multiple keys
* obj: type: object, example: {'key': 'value', 'key2': 'value2', 'key3': {cacheValue: 'value3', expiration: 60}}
* callback: type: function
This function exposes a heirarchy of expiration values as follows:
* The expiration property of a key that also contains a cacheValue property will override all other expirations. (This means that, if you are caching an object, the string 'cacheValue' is a reserved property name within that object.)cacheValue
* If an object with both and expiration as properties is not present, the expiration provided to the .mset() argument list will be used.defaultExpiration
* If neither of the above is provided, each cache's will be applied.
Delete a key or an array of keys and their associated values.
* keys: type: string || array of strings
* callback: type: function
* err: type: object
* count: type: int
Flush all keys and values.
* callback: type: function
With a typical cache setup, you're left to find the perfect compromise between having a long expiration so that users don't have to suffer through the worst case load time, and a short expiration so data doesn't get stale. cache-service-cache-module eliminates the need to worry about users suffering through the longest wait time by automatically refreshing keys for you. Here's how it works:
#### How do I turn it on?
By default, background refresh is off. It will turn itself on the first time you pass a refresh param to .set().
#### Configure
There are three options you can manipulate. See the API section for more information about them.
* backgroundRefreshInterval
*
*
#### Use
Background refresh is exposed via the .set() command as follows:
`javascript`
cacheModule.set('key', 'value', 300, refresh, cb);
If you want to pass refresh, you must also pass cb because if only four params are passed, cache-service-cache-module will assume the fourth param is cb.
#### The Refresh Param
###### refresh(key, cb(err, response))
* key: type: string: this is the key that is being refreshed
* cb: type: function: you must trigger this function to pass the data that should replace the current key's value
The refresh param MUST be a function that accepts key and a callback function that accepts err and response as follows:
`javascript``
var refresh = function(key, cb){
var response = goGetData();
cb(null, response);
}