ShardedMongo

Repository for demonstrating mongo with shards for tuning up server side performance

This is my personal configuration which may not suitable for production mode

In this demo, the 'sharded' database has 2 sharded servers, 2 config server and a mongo router (to distribute queries to shards)

Prerequisite:

docker

On Windows, navigate to Docker home page for download docker desktop

sudo apt install docker.io

docker-compose

Windows/MacOS

As stated in docker compose install page

"Docker Desktop for Mac and Docker Toolbox already include Compose along with other Docker apps", which mean the desktop version of docker includes 'docker-compose'

Linux:

sudo apt install docker-compose

Important On Linux:

Don't forget to append current user to 'docker group' on ubuntu sudo usermod -aG docker $USER

Steps for Mongo sharding:

Create mongo config server (configsvr)
Create mongo shard server (shardsvr)
Create mongo router

What's next ?

Run init scripts on each server to build a 'network'

./init.sh

See comments in init.sh for details

Create a collection and 'sharding' it, example have already run in ./init.sh Some referred documents:
- rs.initiate: https://docs.mongodb.com/manual/reference/method/rs.initiate/, as is documented there, rs.initiate must run on ONLY one mongod instance for the replica set
- about mongod: https://docs.mongodb.com/manual/reference/program/mongod/

To create your own 'sharded' collection (see ./scripts/init-collection.sh as an example):

use test // use the 'test' database (or a database named 'test')
db.createCollection('<collection name>') // create a collection named <collection name>
db.cars.createIndex({<field_for_indexing>: 1}, {unique: true}) // create an index for created collection
sh.shardCollection('test.<collection name>', {<field_for_indexing>: <'hashed' or 1>}, false, {numInitialChunks: <number_of_chunk for 'hashed' index for sharding type}), see document at https://docs.mongodb.com/manual/reference/method/sh.shardCollection/
db.cars.getShardDistribution() // see distribution status

Notes:

We should turn of the mongod service on port 27017 to make mongo container start binding on the port To turn off mongod service:

sudo service mongod stop

Delete all mongo components:

docker-compose down

If you want your volume to be deleted, simply type:

docker-compose down --volumes # ok but not recommended in production

Sometimes, port 27017 are binded, we should check for processes which bind the port to kill them (the process) in order to make docker binds the port. We have another choice: Edit my configuration where port 27017 should be changed

Common problems

You cannot run the ./init.sh You maybe stucked at one of the problems:
- Add execution privilege sudo chmod +x ./init.sh
- docker-compose not installed: Check docker (and docker-compose, on linux, on windows/macos check docker desktop version) or try re-installing docker and docker-compose and run them with 'sudo' privilege (or run as administrator)
- Ports are already in use: Run netstat -lnpt to figure out which processes hangs/bind these port, simply kill them if those processes are not needed