pelageech/BDUTS

Team project "BDUTS Load Balancer"

BDUTS | Load Balancer

The easy Go Load Balancer repository includes a distribution of requests by backends and caching.

Configuration

Backends

Before starting you should configure your backends and put their information to resources/servers.json. For each backend use the following pattern:

[
    {
      "url": "http://192.168.0.1:8080",
      "healthCheckTcpTimeout": 1000
      "maximalRequests": 5
    },
    ...
]

where:

• "url" is the address of the backend to which requests are sent relative to the URL of the load balancer;
• "healthCheckTcpTimeout" is maximum response time from the backend for a tcp packet of the health checker;
• "maximalRequests" is how many requests can be processed on the backend at the same time.

Load Balancer

BDUTS uses HTTPS method, that's why you need to put files MyCertificate.crt and MyKey.key to the root of project.

Then, configure your load balancer in resources/config.json

{
  "port" : 8080,
  "healthCheckPeriod" : 120,
  "maxCacheSize" : 10000000,
  "observeFrequency" : 10000
}

where:

• "port" which the load balancer will listen on;
• "healthCheckPeriod" is a period of checking if all the backends alive;
• "maxCacheSize" is a maximal size in bytes for storing cached pages;
• "observeFrequency" is a period of observing cache in milliseconds and detecting whether it is necessary to delete rotten or little-used pagesю

Let's start our balancer

Just build the project go build . and run it. Or run immediately go run ..

You will see some logs in your terminal:

• All the backends read from JSON-config;
• A result of the first health checking;
• "Load Balancer started at :port".

If you see these logs and there are alive backends, the balancer works!
Let for each backend you have path /hello and the balancer listens on :8080.

Check your load balancer: curl -k https://localhost:8080/hello.
You will see in the logs the backend got the response from the balancer!

Pool of Backends

When you start the load balancer, it reads all the information about backends and creates a server pool. The server pool contains a list of backends and some data about each of them: all the fields from JSON-config and their life status (alive or not).

The balancer uses Weighted Round-Robin algorithm (WRR) for balancing between backends. The pool has a pointer (int index) looking at the last backend that the request was sent to. The beginning value of the pointer is -1, after the first request its value is always between 0 and len(pool) - 1.

The algorithm chooses only alive servers. If the backend is chosen, the request will be sent to this one.
WRR begins again if backend is full of requests (recall that backends have limits on the number of requests processing at the same time).

If the backend doesn't answer or it returns 5xx, it marks not-alive. The backend can become alive again if it passes the next health checker test.

Cache-Proxy

Before sending request the load balancer checks the page in cache. If there is one, the page is read from disk and returned to the client.

The metadata of the page is stored in memory, exactly in boltDB. Before reading it's checked a presence of metadata of the page we're looking for. If everything is OK, the page is read from a disk. If there's no any errors, the page is returned to the client. The balancer sends a request to the backend in case any error is occured.

The load balancer creates a key by key directives from resources/cache_config.json and take a hash of it with hex-encoding. The value saves into request's context. The value always uses if it deals with cache:

Let we have a hash with 128 length:

• Writing: the page will be saved into a specified directory and named
  :root:/cache-data/db/hash[0:31]/hash[32:63]/hash[64:95]/hash[96:127]/hash[:];
• Reading: the balancer will use this hash for searching the page on a disk by the directory above.

Load balancer administration

Sign in

Request

POST /admin/signin HTTP/1.1
Content-Type: application/json; charset=utf-8
Host: localhost:8080
Connection: close

{"username":"username","password":"578XPW76uXa5kqfzv_T6nJhwM30MyRVAOw=="}

Response

HTTP/1.1 200 OK
Authorization: Bearer eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2ODI5MjM5NDcsInVzZXJuYW1lIjoidXNlcm5hbWUifQ.WitBmLpO3gWJOHqVbEfNr6PdGi8B5ZnVaogISUTP_SJdYSgETxh4xarvd8FeTjwF2ZqpB0prN3c6tNRwzNHjIQ
Date: Mon, 01 May 2023 06:32:27 GMT
Connection: close

Sign up

Only existing users can sign up new users.

Request

POST /admin/signup HTTP/1.1
Authorization: Bearer eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2ODI5MjM5NDcsInVzZXJuYW1lIjoidXNlcm5hbWUifQ.WitBmLpO3gWJOHqVbEfNr6PdGi8B5ZnVaogISUTP_SJdYSgETxh4xarvd8FeTjwF2ZqpB0prN3c6tNRwzNHjIQ
Content-Type: application/json; charset=utf-8
Host: localhost:8080
Connection: close

{"username":"username1","email":"mail@gmail.com"}

Response

HTTP/1.1 201 Created
Date: Mon, 01 May 2023 06:35:17 GMT
Connection: close

Delete admin

Request

DELETE /admin?username=admin HTTP/1.1
Authorization: Bearer eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2ODQ1MDY5MzUsInVzZXJuYW1lIjoidXNlcm5hbWUifQ.1TIkZbm-YcoI_r1Z6gAxuQANBBAikeqaB2R7cvdwUO0DgQYwDrMHy8f6SJg66U0IKUPKFQVprAuftFA9Fjwc0Q
Host: localhost:8080
Connection: close

Response

HTTP/1.1 204 No Content
Access-Control-Allow-Headers: *
Access-Control-Allow-Methods: *
Access-Control-Allow-Origin: *
Access-Control-Expose-Headers: Authorization
Date: Fri, 19 May 2023 14:16:00 GMT
Connection: close

Change password

Request

PATCH /admin/password HTTP/1.1
Authorization: Bearer eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2ODI5MzA3MDIsInVzZXJuYW1lIjoidXNlcm5hbWUifQ.34xSq2PUd5B1yDL0XTHpe4MdTcDoryZScNkJpwQJpWyyW45XK64ZAVaXGtL32__aKl1XR1Re-E5NcoqWeYtmXw
Content-Type: application/json; charset=utf-8
Host: localhost:8080
Connection: close

{"oldPassword":"578XPW76uXa5kqfzv_T6nJhwM30MyRVAOw==","newPassword":"1234567890asdf12","newPasswordConfirm":"1234567890asdf12"}

Response

HTTP/1.1 200 OK
Date: Mon, 01 May 2023 08:27:30 GMT
Connection: close

Add server to server pool

Request

POST /serverPool/add HTTP/1.1
Authorization: Bearer eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2ODI5MjkxMDAsInVzZXJuYW1lIjoidXNlcm5hbWUifQ.USR-I-M62r_QTNrr_z-4frwSrGIQRCDyZFOnrqL-3mkRciPh8BUAJk8C0Z58ugUHV3bPrD2jwr4O3qDiwbhXyQ
Content-Type: application/json; charset=utf-8
Host: localhost:8080
Connection: close

{"url":"http://localhost:3038","healthCheckTcpTimeout":2000,"maximalRequests":5}

Response

HTTP/1.1 200 OK
Date: Mon, 01 May 2023 07:58:46 GMT
Content-Type: text/plain; charset=utf-8
Connection: close

Success!

Get servers in server pool

Request

GET /serverPool HTTP/1.1
Authorization: Bearer eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2ODI5MjkxMDAsInVzZXJuYW1lIjoidXNlcm5hbWUifQ.USR-I-M62r_QTNrr_z-4frwSrGIQRCDyZFOnrqL-3mkRciPh8BUAJk8C0Z58ugUHV3bPrD2jwr4O3qDiwbhXyQ
Host: localhost:8080
Connection: close

Response

HTTP/1.1 200 OK
Date: Mon, 01 May 2023 08:01:11 GMT
Content-Type: text/html; charset=utf-8
Connection: close

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Control | BDUTS</title>
</head>
<body>
    <h1>Server Pool</h1>
    <table>
        <thead>
            <tr>
                <th>ID</th>
                <th>URL</th>
                <th>TCP Timeout</th>
                <th>Alive</th>
            </tr>
        </thead>
<tr><td>1</td><td>http://localhost:3031</td><td>2000</td><td>false</td></tr><tr><td>2</td><td>http://192.168.0.5:3031</td><td>2000</td><td>false</td></tr><tr><td>3</td><td>http://localhost:3037</td><td>2000</td><td>false</td></tr><tr><td>4</td><td>http://localhost:3038</td><td>2000</td><td>false</td></tr></table>
<style>
    table, th, td {
        border: 1px solid black;
    }
</style>
</body>
</html>

Delete server from server pool

Request

DELETE /serverPool/remove HTTP/1.1
Authorization: Bearer eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2ODI5MzA3MDIsInVzZXJuYW1lIjoidXNlcm5hbWUifQ.34xSq2PUd5B1yDL0XTHpe4MdTcDoryZScNkJpwQJpWyyW45XK64ZAVaXGtL32__aKl1XR1Re-E5NcoqWeYtmXw
Content-Type: application/json; charset=utf-8
Host: localhost:8080
Connection: close

{"url":"http://localhost:3037"}

Response

HTTP/1.1 200 OK
Date: Mon, 01 May 2023 08:25:12 GMT
Content-Type: text/plain; charset=utf-8
Connection: close

Success!

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