Create a custom endpoint for Analytics Manager queries#

It is possible to easily extend the Analytics Manager query flow by adding new endpoints.
Those endpoints can then be called from any chart in the Front App to be displayed.

Here are some use examples:

• merge 2 queries in one result
• use Machine Learning to compute and display forecast
• do some computation on results before returning them

#Create a new endpoint

Simply add a file in ./src/qb/endpoints/.
This folder does not exist by default, it must be created from the root of the Front API.

For instance, adding the following file provides an answer from a GET request on qb/hello_world : ./src/qb/endpoints/hello_world.js

module.exports = {
  method: "GET",
  request: function(req, res, next) {
    res.send('hello')
  }
}

#Merge two queries

In this example, consider a dataset containing the turnover of Data Platform and 4 other companies. The objective is to compare :

• the evolution of the Data Platform turnover
• the evolution of the sum of all turnover (Data Platform + 4 others).

The Analytics Manager query format needs 2 different queries :

// Data Platform Turnover
{
  "data":{
    "fields":{
      "turnover":["sum"]
    }
  },
  "scale":{
    "fields":["date"]
  },
  "filter":{
    "company": ["Data Platform"]
  }
}
// Global Turnover
{
  "data":{
    "fields":{
      "turnover": ["sum"]
    }
  },
  "scale":{
    "fields":["date"]
  }
}

In order to build a chart with 2 curves in the Front App, the custom endpoint should return the appropriate result set.

const QueryBuilder = require('../../../forepaas/qb/services/QueryBuilder')
const Merge        = require('../../../forepaas/qb/services/Merge')
const Formatter    = require('../../../forepaas/qb/services/Formatter')

module.exports = {
  method: 'GET',
  request: (req, res, next) => {
    // define 2 queries
    let queries = {
      // query 1 : forepaas turnover
      forepaas: {
        data: {
          fields: {
            turnover: ["sum"]
          }
        },
        scale: {
          fields: ["date"]
        },
        filter: {
          company: ["Data Platform"]
        }
      },
      // query 2: global turnover
      global:{
        data: {
          fields: {
            turnover: ["sum"]
          }
        },
        scale: {
          fields: ["date"]
        }
      }
    };

    // execute queries and merge results
    QueryBuilder.queries(req, queries).then(responses => {
      let response = new Merge(responses, { renameWithId:true }).request();
      return Formatter(res, 'json', response);
    }).catch(next)
  }
}

In this example :

1. both queries are made through the QueryBuilder.queries() helper function.
2. responses consist of 2 distinct results : the Front App does not handle it as is.
3. the module Merge offers basic merge functions to accumulate queries.
   The renameWithId option provides two forepaas:turnover and global:turnover fields in return.

#Improve to be dynamic

In most cases, custom endpoints are not simple GET requests that always compute the same request. Usually, the request(s) sent to the Analytics Manager are dynamically generated using the body of the request.
In order to do so, the request's method needs to change to POST and queries passed as variable.

These changes result in the following code:

const QueryBuilder = require('../../../forepaas/qb/services/QueryBuilder')
const Merge        = require('../../../forepaas/qb/services/Merge')
const Formatter    = require('../../../forepaas/qb/services/Formatter')

module.exports = {
  method: 'POST',
  request: (req, res, next) => {
    // define 2 queries from req.body
    let queries = {
      forepaas:{
        ...req.body,
        filter: {
          company: ["Data Platform"]
        }
      },
      global: req.body
    };

    // execute queries and merge results
    QueryBuilder.queries(req,queries).then(responses=>{
      let response = new Merge(responses, { renameWithId:true }).request()
      return Formatter(res, 'json', response)
    }).catch(next)
  }
}

#Call it from the Front App

In the JSON of a Chart, instead of using the request parameter, all you have to do is use the endpoint parameter, as in this example:

{
  "component": "echarts",
  "endpoint": {
    "method": "GET",
    "query": "qb/hello_world",
    "params": {
      "data":{
        "fields":{
          "turnover": ["sum"]
        }
      },
      "scale":{
        "fields":["date"]
      }
    }
  }
}

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