Node.js: Building a Slack Bot with Nodejs Microservices

Node.js: Building a Slack Bot with Nodejs Microservices

Pre-requisites

If you are familiar with creating applications using NodeJS and ExpressJS.

Editor

Visual Studio Code: It is open source and comes with syntax highlighting, intellisense and code formatting for Node. It is written in Nodejs.

Visual studio code

Some Concepts

Miscroservices:

• One Mircoservice should only do one task, like fetching a customer from the backend.
• It should be possible to develop and deploy a microservice completely independent from all the other parts of an application.
• Microservice should communicate using standard HTTP methods.

What are the benefits of Microservices?

• A developer don't have to understand the whole application.
• Services can be developed and deployed by independent teams as there is not much interdependency between those teams.
• Services can be developed with the language that does a given task best or the with which a developer or team is comfortable.
• If the services fails, the whole application doesn't fail, only the service provided by that particular microservice will fail. This is also called resilience.

Slack API

Slack offers a lot of services through its APIs which we can see at Slack API. The Web API provides a way to communicate with slack which is typically a JSON based HTTP API. Under methods, we can see that it provides everything except a way to get messaged pushed to us. So there is one more item under Web API called Real Time Messaging API which can be used for this purpose. You can read more about Real Time Messaging at Slack API RTM. 

Application

Main Application: This application is a web application based on ExpressJS to handle connection to Slack, handle our services, receive messages from Slack, process messages, route messages to a service and send replies to Slack. 

Wit(External Service): This is the service that lets us process natural language to try to understand its meaning. We need it to process the messages.

We will create services that will tell us the local time and weather for a given location which can be extended as we want, all these services are based on ExpressJS. The services need a way to reach to our application and the main application should be able to route the requests or messages to a service that can handle it.

Resilience

What is resilience? Well in simple definition, Resilience is the ability of a substance or object to spring into shape. The ability to recover quickly from difficulties. So how can we make our software architecture more resilient. So imagine in our small slack bot example, where main application is up and the microservice which we developed goes down, our main application might still be running or will throw some error if there is no proper error handling. We can handle the error and get away with this problem but imagine if we have a lot many microservices then we have to do this for every microservice which can lead to possible errors if any services goes down. So some points which we should take care of are:

• No hardwiring of service end-points on the main application.
• Don't fail when is a service is not reachable.

This can be achieved when service has to know the end-point address of the main application to announce itself and to intent it can serve. The main application just have to track the services available and route the requests there which we call it service registry.