Pelias Microservice Wrapper

Overview

Module that provides a convenience wrapper for calling Pelias microservices such as Placeholder or Point-in-Polygon Service over HTTP GET.

Installation

$ npm install pelias-microservice-wrapper

NPM Module

The pelias-microservice-wrapper npm module can be found here:

https://npmjs.org/package/pelias-microservice-wrapper

Usage

This module is primarily used in the Pelias API to call microservices. To add support for a microservice in the API, define a class that derives from ServiceConfiguration, override any methods, and inject into a service instance.

The ServiceConfiguration constructor accepts a string service name (returned by getName() and an object containing the three optional properties:

| property | required | default | description | | --- | --- | --- | --- | | baseUrl | no | none | the base URL used for contacting a service, causes isEnabled() to return false when an empty string | | timeout | no | 1000 | the number of milliseconds a request should wait for a server response before timing out | | retries | no | 3 | the number of retries to attempt before returning an error |

Requests are logged at the debug level when enabled in pelias-config.

Example

const DemoServiceConfig = class extends ServiceConfiguration {
  constructor(configBlob) {
    super('demo microservice', configBlob);
  }
  getUrl(req) {
    return this.baseUrl + '/demo';
  }
  getParameters(req) {
    return {
      size: req.clean.size,
      offset: 0
    };
  }
  getHeaders(req) {
    return {
      'some-header': req.clean.some_header
    };
  }
};

const demoService = serviceWrapper(new DemoServiceConfig({
  url: 'http://localhost:1234'
}));

const req = {
  size: 15,
  some_header: 'header value'
};

// pseudocode tests for illustration purposes
demoService.getUrl() === 'http://localhost:1234/demo';

demoService.isEnabled() === true

demoService.getParameters(req) === {
  size: 15,
  offset: 0
};

demoService.getHeaders(req) === {
  some_header: 'header value'
};

Methods

| method | override? | returns | description | | --- | --- | --- | --- | | getName | not recommended | value passed to constructor | returns the name of the service | | getBaseUrl | not recommended | url property of configuration passed to constructor | base URL of microservice | | isEnabled | not recommended | true if baseUrl is a non-empty string | helper method for determining if the service should be considered enabled | | getUrl | yes | value of getBaseUrl unless overridden | used for appending other value to the baseUrl (but not request parameters) | | getParameters | yes| {} unless overridden | any request parameters to pass to the microservice | | getHeaders | yes | {} unless overridden | any request headers to pass to the microservice | | getTimeout | not recommended | 1000 or value passed to constructor | how long a request should wait for a server response before timing out | | getRetries | not recommended | 3 or value passed to constructor | how many attempts should be made before returning an error |

Recommended ServiceConfiguration Method Overrides

The following methods can be overridden in an implementation of ServiceConfiguration:

| method | default return | description | | --- | --- | --- | | getUrl | value of getBaseUrl | used for appending other value to the baseUrl (but not request parameters) | | getParameters | {} | any request parameters to pass to the microservice | | getHeaders | {} | any request headers to pass to the microservice |

It is not recommended to override any other methods.