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JDBC connection factory

  Class ConnectionManager {   Queue<Connection> availableConnection;   List <Connection> allotedConnection; ConnectionManager( Integer noOfConnections, ConnectionPoperties props ) {     //Create the no of connection objects and assign to avaialbleConnection } Conection getConnection() {     syncronized( this.class) { if (availableConnection.isEmpty() ) {          throw ConnectionExhausted();       }       conn = availableCOnnection.poll();       alottledConectiion.add(conn); } return conn; } synchronized Conection releaseConnection(Connection conn) {        alottedconnection.remove(conn);    avaialbleConection.add(conn); }
Recent posts

Print odd even number using 2 threads

  So we have 2 thread, one will be printing odd numbers and others will be printing even number. We have to print them in a synchronized fashion.  class Lock {     Boolean isOdd;     Lock(Boolean odd) {         this.isOdd = odd;     }     synchronized void print(Integer number) {         Boolean numberEven = number %2 == 0;         while (isOdd == numberEven) {             try {                 wait();             } catch( InterruptedException e) {                Thread.currentThread().interrupt();             }         }         System.out.println(number);         isOdd = !isOdd;         notify();     } } class PrintThread extends Thread{   Integer limit;    Integer value;   Lock lock;   PrintThread( Integer start,Integer limit, Lock lock) {      this.value = start;      this.limit = limit; this.lock = lock;   }       public void run() {    while( value < limit ) {            lock.print(value);    value +=2;         }   } } public class Test {  static public void main(String

Scaling application

 We all wish that our application used by maximum people on Earth. To make sure we have the right scalable application, please follow below guidelines  1. Load balancing at all level of application i.e. web server, application server and DB server 2. Remote caching to be enabled for a fast response.  3. Load balancer will equally distribute the traffic to existing servers, what if enough capacity is not enough. We should have a mechanism to increase the server capacity (esp horizontally ).  All the cloud service provider has provision for autoscaling, so do Kubernetes.  Use them.  4. Most of the NoSQL DB comes with good support for horizontal scalability. So if you chosse NoSQL you can easily scale them. But if your application requires RDBMS (SQL) then plan should be with sharding in place.  5. Server should be stateless. Any server should be able to serve an incoming request. No local storage, no IP binding. Having said newly added server will start serving instantly.  6. CI and CD s

Securing web app

  Use HTTPS - stops "man in middle" attack Use load balancer - control internal vs external applications Input validation mandatory.  2-factor authentication Restrict failed attempt to avoid malicious logins Captcha to avoid the bot. a session should have timeout based on application criticality re-verify login for critical data access  Limit access rate to stop Denial of service attack.  prevent SQL injections     ( "select * from students where student_name =" + name + ";") Encrypt data on 3rd party storage  Hash the passwords 

HTTP/2 : what and why

HTTP History In 1989, the hypertext transfer protocol have been invented. HTTP/1.1 has been released in 1997 and took the longest pause in evolution. In 2015, Google has redrafted its inhouse SPDY protocol to HTTP/2 to optimize the web page load time.  HTTP/1.1 Pitfalls Too heavy and big protocol. Too many parts have been added as optional led to complicating the protocols with less of usage. Since HTTP1.1 release, web technology have seen tremendous change. Page size has been increased to MBs, the number to pages increased manifolds and parallel components making HTTP calls increased too.  Each HTTP request has a separate TCP connection and its handshake does add to page load time.  Head of line blocking has slowed the page load. We can have a maximum 8 parallel connection to the same domain. Due to increase in multiple components making separate HTTP calls, this has been a bottleneck.  HTTP/2 Solution Binary framing layer: HTTP/1.1 was text-only messaging, which was not efficient. HT

gRPC - General Purpose Remote Procedure Call

Google has developed gRPC in 2015 and released it for the world to use. gRPC has been evolved from Stubby,  which Google has been using for all internal communication.  gRPC is open-sourced high-performance RPC framework. It efficiently connects services across machines with pluggable support for load balancing, authentication, monitoring. It supports a wide range of programming language and it can be developed and deployed fast. Microservices architecture does support gRPC communication over service mesh and pretty efficient over REST.  Client libraries in 10 programming languages. gRPC Languages Bidirectional streaming and http/2 supported. pluggable load balancing, auth and monitoring.  Request response and streaming support are available. Strongly typed message definition using Protobuf.  gRPC work like a client-server model. The client will call the framework generated stub (client) to make a service request on a different machine. The server will take the request, execute the ser