// Copyright 2019 Google LLC

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

// [START monitoring_opencensus_metrics_quickstart]

'use strict';

// [START monitoring_opencensus_metrics_dependencies]

const {globalStats, MeasureUnit, AggregationType} = require('@opencensus/core');

const {StackdriverStatsExporter} = require('@opencensus/exporter-stackdriver');

// [END monitoring_opencensus_metrics_dependencies]

const EXPORT_INTERVAL = process.env.EXPORT_INTERVAL || 60;

const LATENCY_MS = globalStats.createMeasureInt64(

'task_latency',

MeasureUnit.MS,

'The task latency in milliseconds'

);

// Register the view. It is imperative that this step exists,

// otherwise recorded metrics will be dropped and never exported.

const view = globalStats.createView(

'task_latency_distribution',

LATENCY_MS,

AggregationType.DISTRIBUTION,

[],

'The distribution of the task latencies.',

// Latency in buckets:

// [>=0ms, >=100ms, >=200ms, >=400ms, >=1s, >=2s, >=4s]

[0, 100, 200, 400, 1000, 2000, 4000]

);

// Then finally register the views

globalStats.registerView(view);

// [START setup_exporter]

// Enable OpenCensus exporters to export metrics to Stackdriver Monitoring.

// Exporters use Application Default Credentials (ADCs) to authenticate.

// See https://developers.google.com/identity/protocols/application-default-credentials

// for more details.

// Expects ADCs to be provided through the environment as ${GOOGLE_APPLICATION_CREDENTIALS}

// A Stackdriver workspace is required and provided through the environment as ${GOOGLE_PROJECT_ID}

const projectId = process.env.GOOGLE_PROJECT_ID;

// GOOGLE_APPLICATION_CREDENTIALS are expected by a dependency of this code

// Not this code itself. Checking for existence here but not retaining (as not needed)

if (!projectId || !process.env.GOOGLE_APPLICATION_CREDENTIALS) {

throw Error('Unable to proceed without a Project ID');

}

// The minimum reporting period for Stackdriver is 1 minute.

const exporter = new StackdriverStatsExporter({

projectId: projectId,

period: EXPORT_INTERVAL * 1000,

});

// Pass the created exporter to Stats

globalStats.registerExporter(exporter);

// [END setup_exporter]

// Record 100 fake latency values between 0 and 5 seconds.

for (let i = 0; i < 100; i++) {

const ms = Math.floor(Math.random() * 5);

console.log(`Latency ${i}: ${ms}`);

globalStats.record([

{

measure: LATENCY_MS,

value: ms,

},

]);

}

/**

* The default export interval is 60 seconds. The thread with the

* StackdriverStatsExporter must live for at least the interval past any

* metrics that must be collected, or some risk being lost if they are recorded

* after the last export.

*/

setTimeout(() => {

console.log('Done recording metrics.');

globalStats.unregisterExporter(exporter);

}, EXPORT_INTERVAL * 1000);

// [END monitoring_opencensus_metrics_quickstart]