rounderdb/lib/Archive.js

A low-I/O, fixed size, round robin db with in-mem support. Store in RAM and sync periodically to disk.

var DataBucket = require('./DataBucket.js');
var debugLog = false;


/* Sample conf for an archive
 [
 {
 capacity: 60, // nr _data points to storage before aggregation occurs to next bucket
 persistence: 'RAM',
 aggregationStrategy: 'average'
 },
 {
 capacity: 2*60,
 persistence: 'file',
 persistenceParams: { path: '/var/log/rounderDB/_data/cpuLoad.dat' },
 aggregationStrategy: 'average'
 }
 ]
 */

/** Constructor.
 * The only argument is optional. It is a convenience param to quickly create an array of buckets.
 * Capacity 60, RAM persistence and 'average' aggregation strategy used as defaults.
 *
 * @param nrBuckets Optional init argument
 * @constructor
 */
function Archive(nrBuckets) {
    this._buckets = [];
    if(!(nrBuckets === undefined) && nrBuckets > 0) {
        for(var i = 0; i < nrBuckets; i++)
            this._buckets.push(new DataBucket(60, 'average'));
    }
}


Archive.createInstance = function(archiveConf) {
    log("ARCHIVE creating from conf: "+JSON.stringify(archiveConf, null, 4));
    var a = new Archive();
    for (var bucket in archiveConf) {
        a.addBucket(DataBucket.createInstance(archiveConf[bucket]));
    }
    log("ARCHIVE: created archive: "+JSON.stringify(a, null, 4));
    return a;
}


Archive.loadInstance = function(dataObj) {
    var a = new Archive();
    dataObj._buckets.map(function(b) {
        a.addBucket(DataBucket.loadInstance(b));
    });
    return a;
}


Archive.prototype.getDataForBucket = function(index) {
    return this._buckets[index].getData();
};

Archive.prototype.add = function (val, timeStamp) {
    if(this._buckets.length == 0)
        throw Error("No buckets available for storage!");

    this._buckets.map(function(bucket, index, buckets) {
        if(index == 0)
            bucket.add(val, timeStamp);
        else if(index >= 1)
            bucket.add(buckets[index-1].aggregate(), timeStamp);

    });

};

Archive.prototype.addBucket = function(bucket) {
    if(!(bucket instanceof DataBucket))
        throw Error("Can only add instances of DataBucket. Got: "+bucket);
    this._buckets.push(bucket);
}

Archive.prototype.getValues = function (bucketIndex) {
    return buckets[bucketIndex].storage.values();
}

Archive.prototype.getNrBuckets = function () {
    return this._buckets.length;
}

Archive.prototype.getBucket = function (index) {
    return this._buckets[index];
}


// Internal helpers below


var log = function (msg) {
    if (debugLog)
        console.log(msg);
};


module.exports = Archive;