boldLabancer

'boldLabancer' is a NodeJS based simple load balancer, handling 3 different endpoints:
GET - /login
POST - /changePassword
POST - /register

Implementation

Every GET request handled is balanced using roundRobin. Every POST requrst is forwarded to all upstreams available, and send to the client the fastest upstream's response using Promise.race.

Possible features/Addons

CommitLog instead of retry forever.
Hot reload of upstreams
Tests
Better logging and handeling exceptions
Native docker support

Installing

Copy this repo

git clone https://github.com/jonatanzafar59/boldLabancer.git
cd boldLabancer/
npm install

CMD

npm start

boldLabancer will listen on port 8080

$ npm start
[1576148437863] INFO  (36841): metrics listeing on 'http://localhost:8080/metrics'
    module: "prometheusClient"
[1576148437865] INFO  (36841): healthCheck listeing on 'http://localhost:8080/health'
    module: "prometheusClient"
[1576148437866] INFO  (36841): boldLabancer is listening on 'http://localhost:8080'
    module: "boldLabancer"

Testing

Mocking upstream servers

In order to check differernt scenarios, we need to start ./src/mockController.js using the following command:

npm run start:mocks

now we have upstream servers running (default is 9), and the controller running on port 5000.

mockServer listening on port 3000
mockServer listening on port 3001
mockServer listening on port 3002
mockServer listening on port 3003
mockServer listening on port 3004
mockServer listening on port 3005
mockServer listening on port 3006
mockServer listening on port 3007
mockServer listening on port 3008
mockController listening on port 5000

every incremented upstream has a higher delay, in order to test the POST Promise.race later (3000 fastest, 3008 slowest).

Testing GET

the upstream getting the request returns its ID.

curl http://localhost:8080/login

test (round robin)

$ curl -s http://localhost:8080/login | jq .
{
  "id": 3000
}
$ curl -s http://localhost:8080/login | jq .
{
  "id": 3001
}
$ curl -s http://localhost:8080/login | jq .
{
  "id": 3002
}
$ curl -s http://localhost:8080/login | jq .
{
  "id": 3003
}

Testing POST

The fastest upstream getting the request returns its ID.

curl -s -X POST http://localhost:8080/changePassword | jq .

test (fastest)

$ curl -s -X POST http://localhost:8080/changePassword | jq .
{
  "id": 3000
}
$ curl -s -X POST http://localhost:8080/changePassword | jq .
{
  "id": 3000
}
$ curl -s -X POST http://localhost:8080/changePassword | jq .
{
  "id": 3000
}

now, we need to kill the fastest upstream, for this we have /killFastestUpstream in mockController:

$ curl -s http://localhost:5000/killFastestUpstream | jq .
{
  "status": "OK",
  "id": 3000
}

we killed upstream with ID 3000. now testing again:

$ curl -s -X POST http://localhost:8080/changePassword | jq .
{
  "id": 3001
}

Metrics

/metrics endpoint returns Promethus format metrics, documented in './src/lib/exporter.js':

boldlabancer_request_time
boldlabancer_error_counter
boldlabancer_request_counter
boldlabancer_upstream_request_counter

curl localhost:8080/metrics

healthCheck

/health endpoint returns status 200:

curl -s  http://localhost:8080/health