README

Helix Status

Report status for OpenWhisk Microservices for Pingdom (and others) Uptime (HTTP) checks

Status

Problem

You have a microservice that is deployed as an OpenWhisk HTTP action or even a number of these microservices and you want to establish monitoring of service uptime using Pingdom.

In case the service is down, you want to quickly understand if it is a problem with

the OpenWhisk runtime, which may be unreachable or overloaded
one of your backend API providers which might be unreachable
your own service which could be broken (for instance due to a deployment change)

Finally, you know that there are Uptime (HTTP) Checks in Pingdom, and similar services such as New Relic Synthetics but you do not want to keep repeating the same code for returning a status check in each of your micro services.

Solution

helix-status is:

a micro service (running as an OpenWhisk HTTP action) that responds to Pingdom Uptime (HTTP) Checks (and similar)
a library that allows you to wrap your own actions to get a standardized monitoring response

Helix Status (as a Service)

Usage

The service is installed and available for Adobe I/O Runtime at https://adobeioruntime.net/api/v1/web/helix/helix-services/status@latest.

curl https://adobeioruntime.net/api/v1/web/helix/helix-services/status@latest/_status_check/pingdom.xml
curl https://adobeioruntime.net/api/v1/web/helix/helix-services/status@latest/_status_check/healthcheck.json

If you want to monitor the availability of Adobe I/O Runtime, just add a new Uptime (HTTP) Check in Pingdom, using the https:// protocol, and adobeioruntime.net/api/v1/web/helix/helix-services/status@latest/_status_check/pingdom.xml as the URL.

Deployment in your own Namespace

If you want to use the service in your own namespace or an OpenWhisk instance that is not Adobe I/O Runtime, make sure your ~/.wskprops is set up correctly and run:

$ npm install
$ npm run build
$ npm run deploy

Helix Status (as a Library)

Installation

$ npm install -S @adobe/helix-status

Usage with Pingdom

In the entry point of your action, add

const { wrap } = require('@adobe/helix-status');

to the top of your file and override the module.exports.main with:

module.exports.main = wrap(main);

All GET /_status_check/pingdom.xml requests to your service will now respond with an XML response similar to below:

<pingdom_http_custom_check>
  <status>OK</status>
  <response_time>0</response_time>

</pingdom_http_custom_check

Note: While the XML response format is similar to the one described in Pingdom Custom HTTP Check the /_status_check/pingdom.xml request is intended to be used for standard Pingdom UPTIME Checks only. It's not suitable for Custom HTTP Checks which expect an HTTP Status 200 XML response whereas UPTIME Checks determine the status of a service (UP/DOWN) based on the HTTP Status code of the response. For more information see #21 and here.

You can also specify a list of checks to run by passing second argument to wrap:

module.exports.main = wrap(main, { example: 'http://www.example.com'})

you will then see results like this:

<pingdom_http_custom_check>
  <status>OK</status>
  <response_time>181</response_time>
  <example>176</example>
</pingdom_http_custom_check>

It is a good idea to use URLs that are representative of the API endpoints your service is calling in normal operation as checks.

Usage with Probot

If you are using Probot for instance through Serverless Probot on OpenWhisk, the usage is slightly different:

// import the probot status app
const { probotStatus } = require('@adobe/helix-status');

probot
  .withApp(yourApp)
  .withApp(probotStatus()) //add a status check app

probotStatus() accepts the same checks object that has been described above, so you can pass an array of URL checks.

Usage with New Relic Synthetics

New Relic Synthetics is a service that is similar to Pingdom. It can be used with helix-status by creating an API Check script like this:

const assert = require('assert');

// replace the URL with your check URL
$http.get('https://adobeioruntime.net/api/v1/web/helix/helix-services/status@v3/_status_check/heathcheck.json',
  // Callback
  function (err, response, body) {
    assert.equal(response.statusCode, 200, 'Expected a 200 OK response');
    const health = JSON.parse(body);
    assert.equal(health.status, 'OK', 'Expected an OK health check status');
    for (const v in health) {
      if (['status', 'process', 'version'].indexOf(v)===-1) {
        $util.insights.set(v, parseInt(health[v]));
      }
    }
    for (const h in ['x-openwhisk-activation-id', 'x-request-id', 'x-version']) {
      $util.insights.set(h, response.headers[h]);
    }
  }
);

Advanced Checks

By default, helix-status will take a map of URLs and make a GET request for each URL provided. In some scenarios, you need to provide additional detail to craft the request and helix-status supports three types of advanced checks for that:

Request Options

If you need to adjust things like request method (from GET to POST) or set request headers (e.g. Accept), instead of providing a URL as string, you can provide a request options object, according to the request/request documentation.

Make sure not to forget the uri.

module.exports.main = wrap(main, 
  { example: {
    uri: 'http://www.example.com',
    method: 'POST',
    headers: {
      accept: 'application/json'
    }
  }});

Custom Status Check Function

For more advanced use cases, you can provide a function in your checks. This function will be executed with the params of your OpenWhisk function when requested with the status check or health check URLs.

Keep in mind that the check function should execute reasonably fast, but it can be async.

module.exports.main = wrap(main, 
  { example: function(params) => params.foo === params.bar });

Request Options with Dynamic Values

A combination of the two techniques above is the usage of request options with Dynamic Values. This can be used if you need to populate properties of the request object or request headers with values provided in the params of the execution.

A typical example would be making a call to an API that requires an API key, where the API key would be stored in the default parameters of the OpenWhisk action.

To achieve this, provide a request options object as described in Request Options, but note that values both of the options and the options.headers object can be functions. Each property that is a function will be replaced with the value that function returns when called with the action's parameters.

module.exports.main = wrap(main, 
  { example: {
    uri: 'http://www.example.com',
    method: 'POST',
    headers: {
      accept: 'application/json',
      authorization: params => `Bearer ${params.EXAMPLE_API_TOKEN}`
    }
  }});

The example above shows how to extract the EXAMPLE_API_TOKEN value from the action's (default) parameters and applies it to the Authorization header.

Status Codes

The health check reports following HTTP status codes:

200 (OK): all health checks performed successfully
504 (Gateway Timeout): the health check took too long to execute
502 (Gateway Error): the health check got an error response from the checked URL
500 (Server Error): the generic check function did not execute successfully

Development

Deploying Helix Status

Deploying Helix Status requires the wsk command line client, authenticated to a namespace of your choice. For Project Helix, we use the helix namespace.

All commits to main that pass the testing will be deployed automatically. All commits to branches that will pass the testing will get committed as /helix-services/status@ci<num> and tagged with the CI build number.

Usage no npm install needed!