Pelias-microservice-wrapper NPM

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