Distributed-Sagas-Defined

😱 This is where the distributed magic happens. 😱

This repository contains implementaion for a generic saga execution coordinator written in TypeScript.

Prerequisites:

Creating a local mongodb replica set

Due to the fact the services composing the saga needs to be idempotent in requests they are processing
they need to be based a persistency solution that supports transactions.

MongoDB 4.0 which is being used in the implementation supports transacion but it requires to be deployed in replica set
in order to do so.

We will create a mongodb replica set named "rs0" for the purpose of running our solution.
cluster will have 3 nodes, and docker will be used to create the entire cluster.

Creating 3 mongo nodes:

docker network create saga-mongo-network
docker run --name mongo-node1 -d -p 37017:37017 --net saga-mongo-network mongo --replSet "rs0" --port 37017
docker run --name mongo-node2 -d -p 37018:37018 --net saga-mongo-network mongo --replSet "rs0" --port 37018
docker run --name mongo-node3 -d -p 37019:37019 --net saga-mongo-network mongo --replSet "rs0" --port 37019

creating the replica set config

docker exec -it mongo-node1 mongo --port 37017

config = {  
      "_id" : "rs0",  
      "members" : [  
          {  
              "_id" : 0,  
              "host" : "mongo-node1:37017"  
          },  
          {  
              "_id" : 1,  
              "host" : "mongo-node2:37018"  
          },  
          {  
              "_id" : 2,  
              "host" : "mongo-node3:37019"  
          }  
      ]  
  }  

// Applying the config.
rs.initiate(config)

// checking replica set is functioning.
rs.status()

Editing host file:

Add the following entries to your host file in order to properly communicate with the replica set.
127.0.0.1 mongo-node1
127.0.0.1 mongo-node2
127.0.0.1 mongo-node3

Connecting to the replica set

Use the following connection string structure to connect to the replica set:

mongodb://mongo-node1:37017,mongo-node2:37018,mongo-node3:37019/?3t.uriVersion=2&3t.connection.name=ConnectionName&readPreference=primary&3t.sharded=true&3t.connectionMode=multi

Creating a database and composing a connection string for the code.

Create a database with any name you want and use the following connection string in the mongo_connection_string env variable
which is defined in the .env file.
mongodb://localhost:37017,localhost:37018,localhost:37019/YourDbName?replicaSet=rs0

Running & Debugging Services:

every service has envtemplate file that represent the needed environment variable definitons rquired for the code.
Create a .env file within the project root folder with your desired config.

Car Service:

npm install
npm start
vs code debug config name: Debug-Car-Service
Api port: 3000
Swagger page: http://localhost:3000/api/

Apartment Service:

npm install
npm start
vs code debug config name: Debug-Apartment-Service
Api port: 3001
Swagger page: http://localhost:3001/api/

Restaurant Service:

npm install
npm start
vs code debug config name: Debug-Restaurant-Service
Api port: 3002
Swagger page: http://localhost:3002/api/

Book a trip SEC Service:

npm install
npm run coverage - istanbul coverage report
npm run test - mocha test with html report