Mongo Change Stream POC

This repo shows how to watch changes in a collection with the ChangeStream API.

It consists of a mongo database with two nodes in replicaset, a watcher container that prints all documents inserted into the "logs" collection, and a generator container that generate random messages and make bulk inserts into the same "logs" collection. The generator container can be started with multiple replicas.

Requirements

• Docker and Docker compose installed
• A copy of Nats Streaming UI

Usage

Setup Mongo replica set

1. First you need to start mongo in replicaset. Start the nodes:

docker-compose up -d mongo0 mongo1

2. Connect to one nodo and set the configuration:

docker exec -it mongo0 mongo

3. Once inside Mongo shell console, set the config and initiate the replicaset:

config={"_id":"rs0","members":[{"_id":0,"host":"mongo0:27017"},{"_id":1,"host":"mongo1:27017"}]}
rs.initiate()

Clone nats-streaming-ui

git clone --depth=1 git@gitlab.com:united-travel-tickets/common/nats-streaming-ui.git 

Start the watcher

Start the ChangeStream watcher container:

docker-compose up mongo-watcher-socket

Start the generators

You can start multiple generators with the scale command:

docker scale nats-generator=10

Set scale to 0 if you want to stop inserting messages into the logs collection

Open logs UI

http://localhost:5000

References

• How to simply set up Mongo's replica set locally with Docker
• go - Watch for MongoDB Change Streams - Stack Overflow
• Using the official MongoDB Go driver