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nft — Flutter boilerplate for newbie

nhancv/nft

Flutter project template. Contribute to nhancv/nft development by creating an account on GitHub.

github.com

For Flutter newbie, who confuses about the template, libraries should use for an initial project

I use this template to set up the initial project. It uses necessary dependencies to start and something you should consider:

Bundle id, app name can be changed easily by search and replace
The app icon had been checked for distribution to stores.
Application clean structure
I18n had been set up and sample
App env approach tested with CI
Compatible with appcenter.ms, bitrise.io (just use appcenter/bitrise for ci, it’ll recognize automatically)
Example of how to use rest API
Example of how to use provider
Example…

Host your own PancakeSwap Testnet

nhancv/pancake-swap-testnet

git clone git@github.com:pancakeswap/pancake-swap-core.git cd pancake-swap-core git checkout -b factory…

github.com

🥞 PancakeSwap - A next evolution DeFi exchange on Binance Smart Chan (BSC)

Flip CAKE, collect SYRUP and stake them with Pancake Swap, the best decentralized exchange on Binance Smart Chain.

pcs.nhancv.com

Preparing source

Clone pancake-swap-core

git clone git@github.com:pancakeswap/pancake-swap-core.git
cd pancake-swap-core
git checkout -b factory 3b214306770e86bc3a64e67c2b5bdb566b4e94a7
yarn install
yarn compile

Clone pancake-swap-periphery

git clone git@github.com:pancakeswap/pancake-swap-periphery.git
cd pancake-swap-periphery
git checkout -b router d769a6d136b74fde82502ec2f9334acc1afc0732
yarn install
yarn add @uniswap/v2-core@"file:../pancake-swap-core"
yarn compile

Clone pancake-swap-interface-v1

git clone git@github.com:pancakeswap/pancake-swap-interface-v1.git
cd pancake-swap-interface-v1
git checkout -b v1 0257017f2daaae2f67c24ded70b5829f74a01b3c
yarn install

Setup

Install contract merger: https://www.npmjs.com/package/sol-merger

npm install sol-merger -g

Prepare `PancakeFactory` and `PancakeRouter`

sol-merger pancake-swap-core/contracts/PancakeFactory.sol ./build
sol-merger pancake-swap-core/contracts/PancakePair.sol ./build
sol-merger pancake-swap-periphery/contracts/PancakeRouter01.sol ./build
sol-merger pancake-swap-periphery/contracts/PancakeRouter.sol ./build…

Install Zabbix — Server Monitor

Config Server

Install here: https://www.zabbix.com/download?zabbix=5.4&os_distribution=ubuntu&os_version=20.04_focal&db=postgresql&ws=nginx
Config server:

nano /etc/zabbix/zabbix_server.conf===>Update DB information

Config frontend web

nano /etc/zabbix/web/zabbix.conf.php
===># Update DB information, must be matched with server config above
....# Integrate with server
ZBX_SERVER = '**your zabbix ip address or name**';
ZBX_SERVER_PORT = '10051';
ZBX_SERVER_NAME = '**your zabbix hostname**';Example
$ZBX_SERVER                     = 'localhost';
$ZBX_SERVER_PORT                = '10051';
$ZBX_SERVER_NAME                = 'zabbix.nhancv.com';

Restart server

sudo systemctl restart zabbix-server
sudo systemctl status zabbix-server
ps -ef | grep zabbix

Setup Agent

Access to vps agent -> Install zabbix-agent

wget https://repo.zabbix.com/zabbix/5.4/ubuntu/pool/main/z/zabbix-release/zabbix-release_5.4-1+ubuntu20.04_all.deb
dpkg -i zabbix-release_5.4-1+ubuntu20.04_all.deb
apt update
apt install zabbix-agent# If you enable firewall -> open ufw port…

Smart contract pagination for list

A contract has an infinite internal storage
There are 2 limits to practicality: gas costs and the block gas limit.

Example

Create 5k5 players, read one time

https://testnet.bscscan.com/address/0x721ff9e58831b698efd26b9ac744cf8f0aaecbc2#readContract

Max Gas Limit is 28,500,000 at May 12, 2021 = 0.22BNB ~ $145

[WRITE] Can add 500 player in 1 tx
[READ] Can not get all 5600 players (1600 is ok)

call to TestPlayerRead.getPlayers
call to TestPlayerRead.getPlayers errored: Error: Internal JSON-RPC error. { "code": -32000, "message": "out of gas" }

[READ] To read all data, should use paging approach

MongoDB Replica Setup

Setup MongoDB


* Check linux version: lsb_release -a
sudo apt install wget
wget -qO - https://www.mongodb.org/static/pgp/server-4.4.asc | sudo apt-key add -

* https://docs.mongodb.com/manual/tutorial/install-mongodb-on-debian/
* Debian 10 "Buster"
echo "deb http://repo.mongodb.org/apt/debian buster/mongodb-org/4.4 main" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.4.list

* https://docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/
* Ubuntu 20.04 (Focal)
echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu focal/mongodb-org/4.4 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.4.list

sudo apt update
sudo apt install -y build-essential
sudo apt install -y mongodb-org
sudo systemctl enable mongod
sudo service mongod start

Controls

- Start: sudo service mongod start
- Verify status: sudo cat /var/log/mongodb/mongod.log …

Node App with PM2 Cluster

PM2 - Cluster Mode

The cluster mode allows networked Node.js applications (http(s)/tcp/udp server) to be scaled across all CPUs available…

pm2.keymetrics.io

Make sure your application is stateless: share database/cache, cronjob

Create ecosystem.config.js at root

// https://pm2.keymetrics.io/docs/usage/application-declaration/
// # Start all applications
// pm2 start ecosystem.config.js
//
// # Stop all
// pm2 stop ecosystem.config.js
//
// # Restart all
// pm2 restart ecosystem.config.js
//
// # Reload all
// pm2 reload ecosystem.config.js
//
// # Delete all
// pm2 delete ecosystem.config.js
module.exports = {
  apps: [{
    name: "nestjs-prod",
    script: "./dist/main.js", …

Read more · 1 min read

Jun 28

Nginx HTTP load balancer

Config:

NGINX Docs | HTTP Load Balancing

Load balancing across multiple application instances is a commonly used technique for optimizing resource utilization…

docs.nginx.com

Simple config: nginx.conf

sudo nano /etc/nginx/sites-available/api.nhancv.com

# start of file
# http {
upstream ncluster {
    server 127.0.0.1:3000 weight=3;
    server 127.0.0.1:3001;
}

server {
    listen…

Read more · 1 min read

Jun 28

Web stress test with JMeter

—

Download

https://jmeter.apache.org/download_jmeter.cgi

Get started

https://jmeter.apache.org/usermanual/get-started.html

INSTRUCTION

Download jmeter -> extract

PREPARE TEST PLAN

open terminal run GUI ./bin/jmeter
Create new Test Plan
Right click on “Test Plan” -> Add -> Threads -> Thread Group -> Update Thread Properties
Right click on “Thread Group” -> Add -> Sampler -> HTTP request -> Update web server and request info
Right click on “Thread Group” -> Add -> Assertions -> Response Assertion -> Add 200 as Response code to Patterns to Test
Right click on “Thread Group” -> Add -> Listener -> View Results in Table
Save config
Click green play button

RUN STRESS TEST

After prepared Test Plan, we got .jmx file
Run command line…

Upgrade mongodb from 3.6.3 to 4.4.4

STOP APPLICATION

BACKUP DATABASE

mongodump --username DB_USERNAME --password DB_PASSWORD --db DB_NAME --out /var/backups/mongobackups/`date +"%m-%d-%y"`

UNINSTALL OLD DATABASE

sudo systemctl stop mongodb
sudo apt-get purge mongodb-*

INSTALL NEW ONE

wget -qO - https://www.mongodb.org/static/pgp/server-4.4.asc | sudo apt-key add -
echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.4 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.4.list
sudo apt-get update
sudo apt-get install -y mongodb-org
sudo systemctl start mongod
sudo systemctl status mongod

VERIFY INSTALLATION

ubuntu@ip-172-31-1-68:~/myubi-wallet-service$ mongod --version
db version v4.4.4
Build Info: {
    "version": "4.4.4",
    "gitVersion": "8db30a63db1a9d84bdcad0c83369623f708e0397",
    "openSSLVersion": "OpenSSL 1.1.1  11 Sep 2018",
    "modules": [],
    "allocator": "tcmalloc",
    "environment": {
        "distmod": "ubuntu1804",
        "distarch": "x86_64",
        "target_arch": "x86_64"
    }
}

Add user role

ubuntu:~$ mongo
> use admin;
> db.createUser({
      user: "admin"…

Read more · 1 min read

Apr 4

Stacking strategy with a fair reward distribution.

The Stack event begins with fixed pool size and stacking time. How to deal with fairy things?
- (1) The reward should be fixed at stacking time and maybe grow…

Read more · 1 min read

Nhan Cao

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nhancv/nft

Flutter project template. Contribute to nhancv/nft development by creating an account on GitHub.

nhancv/pancake-swap-testnet

git clone git@github.com:pancakeswap/pancake-swap-core.git cd pancake-swap-core git checkout -b factory…

🥞 PancakeSwap - A next evolution DeFi exchange on Binance Smart Chan (BSC)

Flip CAKE, collect SYRUP and stake them with Pancake Swap, the best decentralized exchange on Binance Smart Chain.

Preparing source

Setup

Install contract merger: https://www.npmjs.com/package/sol-merger

Prepare PancakeFactory and PancakeRouter

Config Server

Setup Agent

Example

Setup MongoDB

PM2 - Cluster Mode

The cluster mode allows networked Node.js applications (http(s)/tcp/udp server) to be scaled across all CPUs available…

NGINX Docs | HTTP Load Balancing

Load balancing across multiple application instances is a commonly used technique for optimizing resource utilization…

Download

Get started

INSTRUCTION

Download jmeter -> extract

PREPARE TEST PLAN

RUN STRESS TEST

STOP APPLICATION

BACKUP DATABASE

UNINSTALL OLD DATABASE

INSTALL NEW ONE

VERIFY INSTALLATION

Add user role

Nhan Cao

Prepare `PancakeFactory` and `PancakeRouter`