Truyền thuyết kể rằng:

Năm thứ nhất sau Covid-19, anh Tèo, CTO của lele.com, 1 trang web chuyên về gà, đang gặp rắc rối nghiêm trọng về tương lai công ty…

Công ty anh điều hành 1 website gọi gà ở chợ đầu mối, như những web gọi gà khác, trang web của anh có cấu trúc như sau:

Khách hàng sẽ vào trang web của tèo tìm gà, ưng ý bấm chọn, thì browser sẽ gửi request tới server để lấy thông tin của gà được chọn thông qua domain name server( từ đây mình sẽ viết tắt là DNS), DNS này dùng để phiên dịch tên miền lele.com thành IP cho máy dễ hiểu thôi. Sau khi gửi request syn ack các kiểu, giao thức TCP-IP được thành lập thì server sẽ gửi hình của gà cho các bạn xem, và nếu ok sẽ tiến hành bước tiếp theo là đá gà.

Ok mọi chyện sẽ khá bình thường cho đến 1 ngày trang web trở nên nổi tiếng vì dàn gà mới đi thi đoạt giải, dẫn tới số lượng user tăng lên vùn vụt, mỗi ngày có thêm 10 ngàn user, khách nhiều thì tốt nhưng nhiều quá cũng không tốt đẹp gì…Và trang của anh gặp phải vài vấn đề đau đầu:

1. Khi quá nhiều lượt truy cập vào 1 server, băng thông sẽ bị nghẽn và làm chậm tốc độ load web.
2. Số lượng gà mới có profile khủng hơn, cty anh tèo phải cung cấp thêm nhiều thông tin vì khác hàng yêu cầu, dẫn tới sever quá tải. Đầu tư thêm server thì mất công setup network này nọ. Mà upgrade thì web vẫn phải chạy để níu chân khách.
3. Mặc dù khách đông nhưng thường chỉ hoạt động về đêm làm lag server, có những thời điểm web không có khách. Nên đầu tư thêm để ban đêm phí quá.

Nhiều vấn đề không được giải quyết, Tèo quyết định thuê chuyên viên về thay đổi cấu trúc cty. Cuối cùng họ quyết định: Đưa tất cả lên Cloud!

Nhưng có nhiều dịch vụ cung cấp cloud thì chọn cái nào? Xem lại trang web cạnh tranh của Tèo là xemheo.com họ cũng đã chuyển hết Server, cơ sở dữ liệu của họ cho Microsoft Azure. Tèo quyết định không chơi đụng hàng, sau 1 một hồi phân vân và anh chọn AWS vì AWS có giao diện dễ sử dụng hơn:

Amazon Web Services: cung cấp một loạt các sản phẩm dựa trên đám mây trên toàn cầu bao gồm máy tính, lưu trữ, cơ sở dữ liệu, phân tích, mạng, thiết bị di động, công cụ dành cho nhà phát triển, công cụ quản lý, IoT, bảo mật và các ứng dụng doanh nghiệp: theo yêu cầu, khả dụng trong vài giây, trả phí -giá cả tùy ý. Từ kho dữ liệu đến các công cụ triển khai, thư mục đến phân phối nội dung, hơn 175 dịch vụ AWS có sẵn.

Anh Tèo quyết định trở thành khách của AWS. Anh đăng kí mua gói cơ bản, giờ anh có 1 server chạy trên AWS, services thì chạy trên EC2, các backend method đã có Lambda, dữ liệu thì lưu trữ trên S3 bucket, anh còn đang nghiên cứu chuyển qua dùng Kafka cho giống Linkedin vì kafka dữ liệu cập nhật và lưu trữ thông minh hơn. Service của anh giờ còn có chatbot để chat cùng khách hàng và anh được theo dõi toàn bộ server của mình thông qua Amazon Cloud Watch.

Với AWS, Tèo đã phát triển web bán gà của anh thành một thương hiệu International, với quy mô đàn gà 1000 con và nhiều gà ngoại.

Tèo đã xem video sau và thành công, còn bạn thì sao?:

Author:

NGUYEN TRUONG THANH / Software Engineer in Atomotive, Germany

_________________________________________

E-mail: thanhnguyen1181991@gmail.com  

Phone: 004917657997009

GLS it Services, Eschborn, Frankfurt am Main, Germany 

Website: thanhnguyensite.net

In this post I will share experience using linux command, and was we can do and play with a operating system for Developer, or shorter is Linux. You don’t need to know more about this, I will show you how you can create funny program with some Linux command, what you can’t do in Windows.

1. Linux updates and upgrades do not require you to reboot

Re-booting after every software installation or update is very annoying in Windows. I keep wondering why this is not necessary in Linux, but on Windows is rule of tumb – every installation is asking you to re-boot, or after you download the Upgrades annoying window pop up and say – will reboot in 10 minutes, save your work. This is really annoying.

With Linux all you need to do is run : sudo apt update

Then have a cup of coffee until it update your computer.

2. No need to install drivers every time you plug in your computer USB device

OK, I understand that there are custom devices which use uncommon drivers like printers, cameras, etc, but why on earth every time you plug in Windows simple mass storage disk drive, or USB-Serial converter, or Mouse, or Keyboard – devices which are standard and are embedded in every Windows OS after W98 it ALWAYS ask for drivers which are already there? Why on Linux I plug the external HHD or Flash drive and it automatically mounts on my computer and I can work with it, while Windows is asking me for drivers and several minutes scans and show me different windows with warnings and Continue buttons like I’m doing something scaring which may ruin my OS?

3. You can move image/boot-able drive between machines without need for reinstall

Yes! this is something windows users can’t imagine is possible! I do remember back in the dark ages Windows asked me to re-install after I have upgraded the RAM memory size! Now imagine you get your Windows boot-able HDD and plug it on other computer, will it boot? no way!

4. system config in files not registers mess

Now this is one of the most annoying WIndows features – after several months of installing and removing software your registers and windows/system directory becomes so bloated with shared DLLs and mess that some people start making money by writing registry cleaning software!

5. You can’t boot windows from USB Stick

Probably they didn’t find a way to ask you for registration and to collect your money every time they sense this USB is plug to other computer??

6. You cant see this on Windows:

# uptime
15:54PM up 122 days, 11:22, 5 users, load average: 0.12, 0.30, 0.13

every few days if you do not reboot windows machine it starts to act slowly due to the severe memory fragmentation

Python MySQL – Create Database

Last Updated: 09-03-2020

Python Database API ( Application Program Interface ) is the Database interface for the standard Python. This standard is adhered to by most Python Database interfaces. There are various Database servers supported by Python Database such as MySQL, GadFly, mSQL, PostgreSQL, Microsoft SQL Server 2000, Informix, Interbase, Oracle, Sybase etc. To connect with MySQL database server from Python, we need to import the mysql.connector interface.

Syntax:

CREATE DATABASE DATABASE_NAME

importing rquired libraries
 import mysql.connector 
 dataBase = mysql.connector.connect( 
 host ="localhost", 
 user ="user", 
 passwd ="gfg"
 ) 
 preparing a cursor object
 cursorObject = dataBase.cursor() 
 creating database
 cursorObject.execute("CREATE DATABASE geeks4geeks") 

Output:

The above program illustrates the creation of MySQL database geeks4geeks in which host-name is localhost, the username is user and password is gfg.

Let’s suppose we want to create a table in the database, then we need to connect to a database. Below is a program to create a table in the geeks4geeks database which was created in the above program.

importing required library
 import mysql.connector 
 connecting to the database
 dataBase = mysql.connector.connect( 
                     host = "localhost", 
                     user = "user", 
                     passwd = "gfg", 
                     database = "geeks4geeks" ) 
 preparing a cursor object
 cursorObject = dataBase.cursor() 
 creating table
 studentRecord = """CREATE TABLE STUDENT ( 
                 NAME VARCHAR(20) NOT NULL, 
                 BRANCH VARCHAR(50), 
                 ROLL INT NOT NULL, 
                 SECTION VARCHAR(5), 
                 AGE INT, 
                 )"""
 table created
 cursorObject.execute(studentRecord) 
 disconnecting from server
 dataBase.close() 

Output:

MongoDB Python | Insert and Update Data

Prerequisites : MongoDB Python Basics
We would first understand how to insert a document/entry in a collection of a database. Then we would work on how to update an existing document in MongoDB using pymongo library in python. The update commands helps us to update the query data inserted already in MongoDB database collection.

Insert data

We would first insert data in MongoDB.

Step 1 – Establishing Connection: Port number Default: 27017conn = MongoClient(‘localhost’, port-number)If using default port-number i.e. 27017. Alternate connection method:conn = MongoClient()

Step 2 – Create Database or Switch to Existing Database:db = conn.dabasenameCreate a collection or Switch to existing collection:

collection = db.collection_name

Step 3 – Insert : To Insert Data create a dictionary object and insert data in database. Method used to insert data: insert_one() or insert_many()After insert to find the documents inside a collection we use find() command. The find() method issues a query to retrieve data from a collection in MongoDB. All queries in MongoDB have the scope of a single collection.
Note : ObjectId is different for every entry in database collection.
Let us understand insert of data with help on code:

# Python code to illustrate 
# inserting data in MongoDB 
from pymongo import MongoClient 
  
try: 
    conn = MongoClient() 
    print("Connected successfully!!!") 
except:   
    print("Could not connect to MongoDB") 
  
# database 
db = conn.database 
  
# Created or Switched to collection names: my_gfg_collection 
collection = db.my_gfg_collection 
  
emp_rec1 = { 
        "name":"Mr.Geek", 
        "eid":24, 
        "location":"delhi"
        } 
emp_rec2 = { 
        "name":"Mr.Shaurya", 
        "eid":14, 
        "location":"delhi"
        } 
  
# Insert Data 
rec_id1 = collection.insert_one(emp_rec1) 
rec_id2 = collection.insert_one(emp_rec2) 
  
print("Data inserted with record ids",rec_id1," ",rec_id2) 
  
# Printing the data inserted 
cursor = collection.find() 
for record in cursor: 
    print(record) 

Connected successfully!!!
Data inserted with record ids    
{'_id': ObjectId('5a02227b37b8552becf5ed2a'), 
'name': 'Mr.Geek', 'eid': 24, 'location': 'delhi'}
{'_id': ObjectId('5a02227c37b8552becf5ed2b'), 'name':
'Mr.Shaurya', 'eid': 14, 'location': 'delhi'}

Updating data in MongoDB

Methods used: update_one() and update_many()
Parameters passed:
+ a filter document to match the documents to update
+ an update document to specify the modification to perform
+ an optional upsert parameter

# Python code to illustrate 
# updating data in MongoDB 
# with Data of employee with id:24 
from pymongo import MongoClient 
  
try: 
    conn = MongoClient() 
    print("Connected successfully!!!") 
except:   
    print("Could not connect to MongoDB") 
  
# database 
db = conn.database 
  
# Created or Switched to collection names: my_gfg_collection 
collection = db.my_gfg_collection 
  
# update all the employee data whose eid is 24 
result = collection.update_many( 
        {"eid":24}, 
        { 
                "$set":{ 
                        "name":"Mr.Geeksforgeeks"
                        }, 
                "$currentDate":{"lastModified":True} 
                  
                } 
        ) 
  
  
  
print("Data updated with id",result) 
  
# Print the new record 
cursor = collection.find() 
for record in cursor: 
    print(record) 

Output:

Connected successfully!!!
Data updated with id 
{'_id': ObjectId('5a02227b37b8552becf5ed2a'), 
'name': 'Mr.Geeksforgeeks', 'eid': 24, 'location': 
'delhi', 'lastModified': datetime.datetime(2017, 11, 7, 21, 19, 9, 698000)}
{'_id': ObjectId('5a02227c37b8552becf5ed2b'), 'name': 
'Mr.Shaurya', 'eid': 14, 'location': 'delhi'}

To find number of documents or entries in collection the are updated use.

 print(result.matched_count) 

OpenCV is one of the most popular computer vision libraries. If you want to start your journey in the field of computer vision, then a thorough understanding of the concepts of OpenCV is of paramount importance.
In this article, I will try to introduce the most basic and important concepts of OpenCV in an intuitive manner.
This article will cover the following topics:

1. Reading an image
2. Extracting the RGB values of a pixel
3. Extracting the Region of Interest (ROI)
4. Resizing the Image
5. Rotating the Image
6. Drawing a Rectangle
7. Displaying text

This is the original image that we will manipulate throughout the course of this article.

Let’s start with the simple task of reading an image using OpenCV.

Reading an image

Importing the OpenCV library
 import cv2 
 Reading the image using imread() function
 image = cv2.imread('image.png') 
 Extracting the height and width of an image
 h, w = image.shape[:2] 
 Displaying the height and width
 print("Height = {}, Width = {}".format(h, w)) 

Now we will focus on extracting the RGB values of an individual pixel.
Note – OpenCV arranges the channels in BGR order. So the 0th value will correspond to Blue pixel and not Red.

Extracting the RGB values of a pixel

Extracting RGB values.
 Here we have randomly chosen a pixel
 by passing in 100, 100 for height and width.
 (B, G, R) = image[100, 100] 
 Displaying the pixel values
 print("R = {}, G = {}, B = {}".format(R, G, B)) 
 We can also pass the channel to extract
 the value for a specific channel
 B = image[100, 100, 0] 
 print("B = {}".format(B)) 

A class is a user-defined blueprint or prototype from which objects are created. Classes provide a means of bundling data and functionality together. Creating a new class creates a new type of object, allowing new instances of that type to be made. Each class instance can have attributes attached to it for maintaining its state. Class instances can also have methods (defined by its class) for modifying its state.
To understand the need for creating a class let’s consider an example, let’s say you wanted to track the number of dogs which may have different attributes like breed, age. If a list is used, the first element could be the dog’s breed while the second element could represent its age. Let’s suppose there are 100 different dogs, then how would you know which element is supposed to be which? What if you wanted to add other properties to these dogs? This lacks organization and it’s the exact need for classes.
Class creates a user-defined data structure, which holds its own data members and member functions, which can be accessed and used by creating an instance of that class. A class is like a blueprint for an object.
Some points on Python class:
Classes are created by keyword class.
Attributes are the variables that belong to class.
Attributes are always public and can be accessed using dot (.) operator. Eg.: Myclass.Myattribute

<strong>Class Definition Syntax:</strong> class ClassName:     
# Statement-1     
.     .     .     
# Statement-N 
<strong>Defining a class –</strong>

Declaring Objects (Also called instantiating a class)
When an object of a class is created, the class is said to be instantiated. All the instances share the attributes and the behavior of the class. But the values of those attributes, i.e. the state are unique for each object. A single class may have any number of instances.
Example:

Declaring an object

# Python program to
# demonstrate instantiating
# a class


classDog: 

# A simple class
# attribute
attr1 ="mamal"
attr2 ="dog"

# A sample method  
deffun(self): 
print("I'm a", self.attr1)
print("I'm a", self.attr2)

# Driver code
# Object instantiation
Rodger =Dog()

# Accessing class attributes
# and method through objects
print(Rodger.attr1)
Rodger.fun()

Output:
mamal I’m a mamal I’m a dog
In the above example, an object is created which is basically a dog named Rodger. This class only has two class attributes that tell us that Rodger is a dog and a mammal.
The self
Class methods must have an extra first parameter in method definition. We do not give a value for this parameter when we call the method, Python provides it.
If we have a method which takes no arguments, then we still have to have one argument.
This is similar to this pointer in C++ and this reference in Java.
When we call a method of this object as myobject.method(arg1, arg2), this is automatically converted by Python into MyClass.method(myobject, arg1, arg2) – this is all the special self is about.
__init__ method:
The __init__ method is similar to constructors in C++ and Java. Constructors are used to initialize the object’s state. Like methods, a constructor also contains a collection of statements(i.e. instructions) that are executed at the time of Object creation. It is run as soon as an object of a class is instantiated. The method is useful to do any initialization you want to do with your object.

# A Sample class with init method 
classPerson: 

# init method or constructor  
def__init__(self, name): 
self.name =name 

# Sample Method  
defsay_hi(self): 
print('Hello, my name is', self.name)

p =Person('Nikhil') 
p.say_hi() 

 
Output:
Hello, my name is Nikhil
Class and Instance Variables
Instance variables are for data unique to each instance and class variables are for attributes and methods shared by all instances of the class. Instance variables are variables whose value is assigned inside a constructor or method with self whereas class variables are variables whose value is assigned in the class.
Defining instance varibale using constructor.

Output:
Rodger details: Rodger is a dog Breed: Pug Color: brown Buzo details: Buzo is a dog Breed: Bulldog Color: black Accessing class variable using class name dog
Defining instance variable using the normal method.