ACID - Dirty Read ve Dirty Write - Commitlenmemiş Veriye Erişmek

Giriş

Şeklen şöyle

SQL Server için şeklen şöyle

Dirty Read

Kısaca commit'lenmemiş bir transaction'a ait veriyi okumak anlamına gelir. Bizim transaction'ımız diğer transaction'a ait veriyi okur, ancak daha sonra diğer transaction rollback yapmaya karar verir. Bu durumda Dirty Read olur. Açıklaması şöyle

A dirty read happens when a transaction is allowed to read the uncommitted changes of some other concurrent transaction. Taking a business decision on a value that has not been committed is risky because uncommitted changes might get rolled back.

Dirty Write

Bir  transaction, bir başka transaction'a ait veriyi de yazar, ancak daha sonra diğer transaction rollback yapmaya karar verir. Bu durumda Dirty Write olur 

Content Delivery Network - CDN

Giriş

Açıklaması şöyle. CDN sık kullanılan şeyleri cache'ler

A CDN is a network of servers that are distributed around the world, and are used to deliver content to users based on their location.

When a user requests content from a CDN, the closest server to the user will deliver the content, rather than having the user’s request be routed to the origin server. The content is then cached on the CDN server, so that if another user in the same location requests the same content, it can be quickly delivered from the cache.

Açıklaması şöyle. Cache'lenen şey herhangi bir şey olabilir. 

They allow websites to cache frequently accessed assets — such as pictures, videos, or JavaScript files — to make the website more performant and avoid downtime.

Açıklaması şöyle

Also, there are generally two kinds of CDNs conceptually

1. Push CDN: You are responsible to upload data to the CDN servers

2. Pull CDN: The CDN will pull data from your servers (origin servers)

Google Cloud

Giriş

AWS ve Google Cloud karşılaştırması şeklen şöyle

Bir başka yazı burada

Google Cloud Dataflow

Serverless stream ve batch processing içindir.

Google Cloud Shell

Linux bilgisayar gibi. python3, git, docker gibi komutlar mevcut. 

gcloud komutu

gcloud komutu yazısına taşıdım

MemoryStore

Açıklaması şöyle

Redis is a popular open source in memory database. It is available as a managed service on AWS (Elasticache) and Google Cloud (Memorystore).

Push Notification

Açıklaması şöyle

Notifications of Whatsapp and Reddit are triggered by push notifications sent from Google servers, received by Google Play Services, a system app which always runs in background.

Depending on the received push notification type such a push notification can be displayed directly without even starting the app it is targeting or the push message is delivered to the app (which is automatically started if it is not already running) and the app can then "translate" the push message into a notification (in case of Whatsapp this require e.g. decryption of the received message or even fetching additional data from Whatsapp servers).

Bigtable

Google Cloud Veri Tabanları yazısına taşıdım

BigQuery

Google Cloud Veri Tabanları yazısına taşıdım

Pub/Sub

Google Cloud Pub/Sub yazısına taşıdım

Google Cloud Storage

Google Cloud Storage yazısına taşıdım

Google Cloud Functions

Serverless ve event driven geliştirme imkanı sağlar. AWS karşılığı Lambda, Azure karşılığı ise Azure Functions

Google Cloud WorkFlows

Açıklaması şöyle

A cloud-based workflow engine managed by Google Cloud. Workflows can be defined in either YAML or JSON format. Furthermore, the orchestrator uses HTTP to interact with the tasks.

Google Kubernetes Engine (GKE)

Google Cloud - Google Kubernetes Engine (GKE) yazısına taşıdım

Http Long Polling

Giriş

Açıklaması şöyle

In long polling, clients can request information from the server to expect that the server may not respond immediately. If the server has no new data for the client when the poll is received, instead of sending an empty response, the server holds the request open and waits for response information to become available. Once it does have new information, the server immediately sends the response to the client, completing the open request. Upon receipt of the server response, the client can immediately issue another server request for future updates. This gives a lot of improvements in latencies, throughputs, and performance. However, the long polling request can timeout or receive a disconnect from the server. In that case, the client has to open a new request.

Trigonometrik Fonksiyonlar - PI Sayısı

Hazır Sabitler

Örnek - C ve C++

Şöyle yaparız

#include <math.h>
M_PI şeklinde kullanılır

Örnek - C++ - 20

Şöyle yaparız

std::numbers::pi

Kendimiz Hesaplarsak

Örnek - C++

Şöyle yaparız

static const double PI = std::atan(1) * 4;

Örnek - C#

Şöyle hesaplanabilir.
4∗(1−13+15−17+…)
Kod olarak şöyle yaparız. Bölümdeki böleni hep 2 artırırız. Bölme işlemi bir artı bir de eksi olacak işareti ile toplama eklenir.

double number = 0;
double pi;
int i = 1;

do 
{
  if ((i/2) % 2 == 0)
  {
    number += (double)(1) / i;
  }
  else
  {
    number -= (double)(1) / i;
  }
  pi = 4 * number;
  i += 2;
} while (Math.Round(pi,5) != 3.14159);

Trigonometrik Fonksiyonlar - Sinüs

Giriş

Sinüs temel trigonometrik fonksiyonlardan birisi. sin (sinüs) fonksiyonu ile dikkat edilmesi gereken nokta, sin (PI) çağrısı sonucunda,  PI sayısı floating sayı olarak tam temsil edilemediğinden 0'ı vermeyebilir.

Çıktı Birimi
Sinüs radyan cinsinden çalışır. Dolayısıyla şöyle yapmak gerekir.

public static double sin(double angle){    
  angle = Math.toRadians(angle);
  return Math.sin(angle);
}

Sinüs  Hesaplama

Örnek
sinüsü hesaplamak için Taylor Serisi kullanılabilir.

Örnek

Tablo kullanarak hesaplanabilir.

HTTP/3 - HTTP over QUIC

Tarayıcı Desteği

Tarayıcımızın HTTP/3 destekleyip desteklemediğini görmek için  quic.nginx.org adresine gidilebilir.

TCP Kullanmıyor, QUIC Kullanıyor

Açıklaması şöyle.

Instead of TCP, HTTP/3 uses a new protocol, developed in 2012 by Google, called QUIC (pronounced “quick”).

QUIC'in Özellikleri

Bazı özellikleri şöyle

- Instead of TCP, HTTP/3 uses a new protocol, QUIC, developed by Google in 2012. QUIC runs over UDP, the User Datagram Protocol.

- QUIC provides native multiplexing, and lost packets only impact the streams where data has been lost. This resolves the head-of-line blocking issue in HTTP/2.

- QUIC provides flow control for stream data and all HTTP/3 frame types that are sent on streams. Therefore, all frame headers and payloads are subject to flow control.

- The request and response headers are compressed by QPACK instead of HPACK in HTTP/2.

- Several HTTP/3 frames are used to manage server push.

Native Multiplexing

Bu sayede sayfayı paralel yüklemek mümkün. Açıklaması şöyle.

Before HTTP/2, browsers could only send one request to the server at a time. This made website loading significantly slower because the browser only loaded one asset, like CSS or JavaScript, at a time. HTTP/2 introduced the ability to load more than one asset at a time, but TCP was not made for this. If one of the requests failed, TCP would make the browser redo all the requests. Because TCP was removed in HTTP/3 and replaced by QUIC, HTTP/3 solved this problem. With HTTP/3, the browser only needs to redo the failed request. Because of this, HTTP/3 is faster and more reliable.

TLS

Açıklaması şöyle. QUIC protokolü de TLS kullanıyor

HTTP/3 optimizes the “handshake” that allows browsers HTTP requests to be encrypted. QUIC combines the initial connection with a TLS handshake, making it secure by default and faster.