first commit

batch/scheduler/capacity/fixed.js

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+'use strict';
+
+function FixedCapacity(capacity) {
+    this.capacity = Math.max(1, capacity);
+}
+
+module.exports = FixedCapacity;
+
+FixedCapacity.prototype.getCapacity = function(callback) {
+    return callback(null, this.capacity);
+};

batch/scheduler/capacity/http-load.js

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+'use strict';
+
+var util = require('util');
+var debug = require('../../util/debug')('capacity-http-load');
+var HttpSimpleCapacity = require('./http-simple');
+
+function HttpLoadCapacity(host, capacityEndpoint) {
+    HttpSimpleCapacity.call(this, host, capacityEndpoint);
+}
+util.inherits(HttpLoadCapacity, HttpSimpleCapacity);
+
+module.exports = HttpLoadCapacity;
+
+HttpLoadCapacity.prototype.getCapacity = function(callback) {
+    this.getResponse(function(err, values) {
+        var capacity = 1;
+
+        if (err) {
+            return callback(null, capacity);
+        }
+
+        var cores = parseInt(values.cores, 10);
+        var relativeLoad = parseFloat(values.relative_load);
+
+        capacity = Math.max(1, Math.floor(((1 - relativeLoad) * cores) - 1));
+
+        capacity = Number.isFinite(capacity) ? capacity : 1;
+
+        debug('host=%s, capacity=%s', this.host, capacity);
+        return callback(null, capacity);
+    }.bind(this));
+};

batch/scheduler/capacity/http-simple.js

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+'use strict';
+
+var request = require('request');
+var debug = require('../../util/debug')('capacity-http-simple');
+
+function HttpSimpleCapacity(host, capacityEndpoint) {
+    this.host = host;
+    this.capacityEndpoint = capacityEndpoint;
+
+    this.lastResponse = null;
+    this.lastResponseTime = 0;
+}
+
+module.exports = HttpSimpleCapacity;
+
+HttpSimpleCapacity.prototype.getCapacity = function(callback) {
+    this.getResponse(function(err, values) {
+        var capacity = 1;
+
+        if (err) {
+            return callback(null, capacity);
+        }
+
+        var availableCores = parseInt(values.available_cores, 10);
+
+        capacity = Math.max(availableCores, 1);
+        capacity = Number.isFinite(capacity) ? capacity : 1;
+
+        debug('host=%s, capacity=%s', this.host, capacity);
+        return callback(null, capacity);
+    }.bind(this));
+};
+
+HttpSimpleCapacity.prototype.getResponse = function(callback) {
+    var requestParams = {
+        method: 'POST',
+        url: this.capacityEndpoint,
+        timeout: 2000,
+        json: true
+    };
+    debug('getCapacity(%s)', this.host);
+
+    // throttle requests for 500 ms
+    var now = Date.now();
+    if (this.lastResponse !== null && ((now - this.lastResponseTime) < 500)) {
+        return callback(null, this.lastResponse);
+    }
+
+    request.post(requestParams, function(err, res, jsonRes) {
+        if (err) {
+            return callback(err);
+        }
+        if (jsonRes && jsonRes.retcode === 0) {
+            this.lastResponse = jsonRes.return_values || {};
+            // We could go more aggressive by updating lastResponseTime on failures.
+            this.lastResponseTime = now;
+
+            return callback(null, this.lastResponse);
+        }
+        return callback(new Error('Could not retrieve information from endpoint'));
+    }.bind(this));
+};