feat: add histogram metric

Author: Velmisov

src/index.js

@@ -4,6 +4,7 @@ import PullTransport from './transport/PullTransport';
 import PushTransport from './transport/PushTransport';
 import Metric from './metric/Metric';
 import GaugeMetric from './metric/GaugeMetric';
+import HistogramMetric from './metric/HistogramMetric';
 
 export {
   UMetrics,
@@ -12,4 +13,5 @@ export {
   PullTransport,
   GaugeMetric,
   Metric,
+  HistogramMetric,
 };

src/metric/HistogramMetric.js

@@ -0,0 +1,44 @@
+import promClient from 'prom-client';
+import Metric from './Metric';
+
+class HistogramMetric extends Metric {
+  constructor(name, buckets = [], options = {}) {
+    super(name, options);
+
+    this.promMetric = new promClient.Histogram({
+      name: this.name,
+      help: options.help || `${this.name}_help`,
+      labelNames: Object.keys(this._labels),
+      buckets,
+    });
+  }
+
+  /**
+   * @param {string} action
+   * @param {number} value
+   * @param {Object.<string, string | number>} [_labels]
+   * @return {HistogramMetric}
+   * @private
+   */
+  _proxyCall(action, value, _labels) {
+    const labels = { ...this._labels, ..._labels };
+    if (!labels) {
+      this.promMetric[action](value);
+      return this;
+    }
+
+    this.promMetric[action](labels, value);
+    return this;
+  }
+
+  /**
+   * @param {number} value
+   * @param {Object.<string, string | number>} [labels]
+   * @returns {HistogramMetric}
+   */
+  observe(value, labels) {
+    return this._proxyCall('observe', value, labels);
+  }
+}
+
+export default HistogramMetric;

src/metric/HistogramMetric.server.test.js

@@ -0,0 +1,99 @@
+import { expect } from 'chai';
+import promClient from 'prom-client';
+import HistogramMetric from './HistogramMetric';
+
+/**
+ * @param {string} metricName
+ * @return {number}
+ */
+const getMetricValues = metricName =>
+  promClient.register.getSingleMetric(metricName).get().values;
+
+/**
+ * @param {string} metricName
+ * @param {string} labelName
+ * @return {string|number}
+ */
+const getLabelValue = (metricName, labelName) =>
+  promClient.register.getSingleMetric(metricName).get().values[0].labels[
+    labelName
+  ];
+
+describe('HistogramMetric', () => {
+  // Чтобы не ебалось при --watch
+  afterEach(() => {
+    promClient.register.clear();
+  });
+
+  it('Can observe value without labels', () => {
+    const metricName = 'test';
+
+    const metric = new HistogramMetric(metricName, [5, 100, 1000]);
+
+    metric.observe(5);
+    metric.observe(50);
+    metric.observe(100);
+    metric.observe(1001);
+
+    const metricValues = getMetricValues(metricName);
+
+    expect(metricValues[0].labels.le).to.be.equal(5);
+    expect(metricValues[0].value).to.be.equal(1);
+    expect(metricValues[0].metricName).to.be.equal(`${metricName}_bucket`);
+
+    expect(metricValues[1].labels.le).to.be.equal(100);
+    expect(metricValues[1].value).to.be.equal(3);
+
+    expect(metricValues[2].labels.le).to.be.equal(1000);
+    expect(metricValues[2].value).to.be.equal(3);
+
+    expect(metricValues[3].labels.le).to.be.equal('+Inf');
+    expect(metricValues[3].value).to.be.equal(4);
+
+    expect(metricValues[4].value).to.be.equal(1156);
+    expect(metricValues[4].metricName).to.be.equal(`${metricName}_sum`);
+  });
+
+  it('Can observe value with labels', () => {
+    const metricName = 'test';
+    const labelName = 'testLabel';
+
+    const metric = new HistogramMetric(metricName, [100], {
+      labels: { testLabel: null },
+    });
+
+    metric.observe(50, { [labelName]: 'testLabel' });
+    metric.observe(150, { [labelName]: 'testLabel' });
+
+    const labelValue = getLabelValue(metricName, labelName);
+    expect(labelValue).to.be.equal(labelName);
+
+    const metricValues = getMetricValues(metricName);
+    expect(metricValues[0].labels.le).to.be.equal(100);
+    expect(metricValues[0].value).to.be.equal(1);
+    expect(metricValues[0].metricName).to.be.equal(`${metricName}_bucket`);
+
+    expect(metricValues[1].labels.le).to.be.equal('+Inf');
+    expect(metricValues[1].value).to.be.equal(2);
+
+    expect(metricValues[2].value).to.be.equal(200);
+    expect(metricValues[2].metricName).to.be.equal(`${metricName}_sum`);
+  });
+
+  it('Can observe value without buckets', () => {
+    const metricName = 'test';
+
+    const metric = new HistogramMetric(metricName);
+
+    metric.observe(50);
+    metric.observe(150);
+
+    const metricValues = getMetricValues(metricName);
+
+    expect(metricValues[0].labels.le).to.be.equal('+Inf');
+    expect(metricValues[0].value).to.be.equal(2);
+
+    expect(metricValues[1].value).to.be.equal(200);
+    expect(metricValues[1].metricName).to.be.equal(`${metricName}_sum`);
+  });
+});