jsdon-ld-context-cache

Caching json-ld context lookups for performance and network access control.

See http://manu.sporny.org/2016/json-ld-context-caching/ for details on why context caches are needed.

Essentially, by caching json-ld URL lookups, the time for applying json-ld normalization is vastly reduced.

The https://github.com/msporny/json-jsonld-basic-perftest shows how this may be applied.

Replace the jsonld node module "documentLoader" function with a cache lookup.
Original cache example:

``javascript
var async = require('async');
var fs = require('fs');
var jsonld = require('jsonld');

var ctx = fs.readFileSync('../contexts/schema.org.jsonld', 'utf8');
var CONTEXTS = {'http://schema.org/': ctx};

jsonld.documentLoader = function(url, callback) {
if(url in CONTEXTS) {
return callback(
null, {
contextUrl: null, // this is for a context via a link header
document: CONTEXTS[url], // this is the actual document that was loaded
documentUrl: url // this is the actual context URL after redirects
});
} else {
throw new Error('invalid context: ' + url);
}
};
``

#using json-ld-context-cache

jsonld now supports a documentLoader options parameter.

`javascript
var jsonld = require('jsonld');
var jsonldcache = require('jsonldcache')( { contextDir: __dirname + '/../contexts', log :logger.info } );
var options = {documentLoader:jsonldcache.documentLoader};

function logObj( msg ){
return function(err,obj){
if( err ) {
logger.info( ${msg} Error ${err});
}else{
var res = JSON.stringify(obj,null,2);
logger.info( ${msg} : ${res} );
}
};
}

jsonld.expand(jsonObject, options, logObj(${fname} expand) );

``