kinvey-backend-sdk

Kinvey Backend SDK (beta)

This is the SDK for Backend code execution for kinvey-hosted Data Link Connectors and Logic tasks. The module provides a framework for building kinvey-backed Data Link Connectors easily.

This module provides an easy way to connect to a Kinvey Business Logic (BL) instance running on docker. It is up to the user to download, configure and start the docker image itself before running code using this module. Two utility functions are provided to automate setting up the docker image.

Installation

To install this project, add it to your package.json file and install it via npm

npm install kinvey-backend-sdk

To use this module, require it in your project and

const sdk = require('kinvey-backend-sdk');

You then must initialize the sdk to retrieve a reference to the backend service:

const service = sdk.service((err, service) => {
  // code goes here
};

When running locally, you can specify a host and port to listen on by passing an options object with an optional host and port. If no host/port is specified, localhost:10001 will be used:

const service = sdk.service({ host: 'somehost', port: 7777 }, (err, service) => {
  // code goes here
};

To run your code locally, execute node . in the root of your project. Routes conform to the Kinvey Data Link specification.

DataLink framework

The DataLink framework can be accessed via the sdk's dataLink property.

const dataLink = sdk.dataLink;

Registering ServiceObjects

The backend SDK works by defining ServiceObjects, and then wiring up data access event handlers to those ServiceObjects. To register a ServiceObject, use the serviceObject method of the dataLink framework:

// To register the 'widgets' ServiceObject:
const widgets = sdk.dataLink.serviceObject('widgets');

Data Events

Each ServiceObject exposes data events that are invoked by Kinvey collections. The data event takes a single handler function to be executed.

event	description
onInsert	executed on inserts (or POST to REST API)
onUpdate	executed on updates (or PUT to the REST API)
onDeleteById	executed when a single entity is to be deleted
onDeleteByQuery	executed when a query is included as part of a DELETE
onDeleteAll	executed when the DELETE command is invoked
onGetById	get a single entity by Id
onGetByQuery	retrieve results based on a query
onGetAll	get all entities in a given ServiceObject
onGetCount	get the count of the entities in a ServiceObject
onGetCountByQuery	get the count of the entities in a query result

For example, to get all entities in widgets:

widgets.onGetAll(callbackFunction);

Data Handler Functions

The data events take a handler funciton, which takes two arguments: request and complete. request represents the request made to Kinvey, and complete is a completion handler for ending BL.

request object

The request object contains the following properties

property	description
method	the HTTP method (GET, POST, PUT, DELETE)
headers	the HTTP request headers
entityId	executed when the DELETE command is invoked on a serviceObject
serviceObjectName	the name of the serviceObject
body	the HTTP body
query	the query object

Completion Handler

The completion handlers object follows a builder pattern for creating the datalink's response. The pattern for the completion handler is complete(<entity>).<status>.<done|next>

For example, a sample completion handler is:

complete(myEntity).ok.next()

complete

The complete handler takes either an entity, an array of entities, or an error description. The result of the complete handler is an object of status functions.

// Sets the response to include an entity.
complete({"foo", "bar"});

// Sets the response to include an array of entities
complete([{"foo":"bar"}, {"abc":"123}]);

// Sets the response to an error string, to be used with error status codes
complete("Record 123 was not found");

status functions

Status functions set the valid status codes for a Data Link Connector. The status function also sets the body to a Kinvey-formatted error, and uses the value passed into the complete function as the debug property, if it is present.

The available status functions are:

Function	Status Code	Description
ok	200	Used for a normal success response
created	201	Used for creating new records
accepted	202	Used when the request has been submitted for processing, but will be processed asynchronously
notFound	404	Used when the entity or entities could not be found
badRequest	400	Used when the request is invalid
unauthorized	401	Used when the request has not been authorized for the given user context
forbidden	403	Used when the specific request is forbidden for some reason
notAllowed	405	Used when the specific request or request method is not allowed
notImplemented	501	Used when the specific handler has no implementation
runtimeError	550	Used for custom runtime errors

For example:

// Return that the record has been created
complete(myRecord).created();

// Entity wasn't found
complete("The given entity wasn't found").notFound();

End processing

Once the status is set, you can end the processing of the dataLink request with either done or next. Most requests should normally end with next, which will continue the Kinvey request pipeline with Business Logic. done will return the response that was set in the DataLink, and end request processing without executing any further business logic.

// This will continue the request chain
complete(myEntity).ok().next();

// This will end the request chain with no further processing
complete(myEntity).ok().done();

Example

The following is an example

const sdk = require('kinvey-backend-sdk');
const service = sdk.service(function(err, service) {
  const dataLink = service.dataLink;   // gets the datalink object from the service

  const getRecordById = function(request, complete) {
    let entityId = request.entityId;
    let entity = null;

    // Do some logic to get the entity id from the remote data store
    // Assume that data is retrieved and stored in "entity" variable

    // After entity is retrieved, check to see if it exists
    if (typeof entity === 'undefined' || entity === null || entity === {}) {
      return complete("The entity could not be found").notFound().next();
    } else  {
      // return the entity
      return complete(entity).ok().next();
    }
  }

  // set the serviceObject
  const widgets = dataLink.serviceObject('widgets');

  // wire up the event that we want to process
  widgets.onGetById(getRecordById);

  // wire up the events that we are not implementing
  widgets.onGetByQuery(notImplementedHandler);
  widgets.onGetAll(notImplementedHandler);
  widgets.onGetCount(notImplementedHandler);
  widgets.onInsert(notImplementedHandler);
  widgets.onUpdate(notImplementedHandler);
  widgets.onDeleteAll(notImplementedHandler);
  widgets.onDeleteByQuery(notImplementedHandler);
  widgets.onDeleteById(notImplementedHandler);
};

Changelog

0.4.1

• Added support for business logic handler discovery
• Modified service discovery response structure