Web Technology Experts Notes

Wednesday, 10 September 2014

Nginx Server interview Questions and Answers

What is Nginx Server?
Nginx is an open source web server and a reverse proxy server for HTTP, SMTP, POP3, and IMAP protocols with a strong focus on high concurrency, performance and low memory usage. It is pronounced as "engine x".

Who is Author of Nginx?
Igor Sysoev

In which Language Nginx is Written?
'C' Language

What is offical website of Nginx?
nginx.org

When Nginx's stable version launched?
5 August 2014

What is the Best Usage of Nginx Server?
Nginx can deploy dynamic HTTP content on a network with using of SCGI, FastCGI handlers for scripts, WSGI application servers or Phusion Passenger module. Nginx can also serve as a load balancer.

What is the Difference between Apache Web Server and Nginx?
Nginx uses an asynchronous event approach to handling multiple requests whereas Apache Web Server use the synchronous. Nginx's event-driven approach can provide more predictable performance under high loads.

Apache Web Server handling multiple request
|----A-----||-----B-----------||-------C------|

Nginx handling multiple request
|----A-----|
|-----B-----------|
|-------C------|
In this way, Nginx is far better than Apache.

What are Features of Nginx?

Simultaneous Connections with low memory
Auto Indexing
Load Balancing
Reverse Proxy with Caching
Fault Tolerance

What are all feature of Nginx Server?

Ability to handle more than 10,000 simultaneous connections with a low memory.
Handling of static files, index files, and auto-indexing
Reverse proxy with caching
Load balancing with in-band health checks
Fault tolerance
TLS/SSL with SNI and OCSP stapling support, via OpenSSL.
FastCGI, SCGI, uWSGI support with caching
FastCGI via PHP (PHP-FPM) support with caching
Name- and IP address-based virtual servers
IPv6-compatible
SPDY protocol support
WebSockets and HTTP/1.1 Upgrade (101 Switching Protocols)
FLV and MP4 streaming
Web page access authentication
gzip compression and decompression
URL rewriting
Custom logging with on-the-fly gzip compression
Response rate and concurrent requests limiting
Server Side Includes
IP address-based Geo-Location
User tracking
WebDAV
XSLT data processing
Embedded Perl scripting
TLS/SSL support
STARTTLS support
SMTP, POP3, and IMAP proxy
Authentication using an external HTTP server
Upgrading executable and configuration without client connections loss and a module-based architecture.

What is the Master and Worker Processes in Nginx Server?
Master process read and evaluate configuration, and maintain worker processes.
Worker processes do actual processing of requests.

Where the Process ID does for Nginx Server?
The process ID of the master process is written in the file /usr/local/nginx/logs/nginx.pid

What are the controls used in Nginx Server?
Nginx -s [stop | quit | reopen | reload]

What is the purpose of –s with Nginx Server?
-s parameter is used to run the executable file of nginx.

How to add Modules in Nginx Server?
Nginx modules must be selected during compile.
Run-time selection of modules is not supported by Nginx.

Friday, 5 September 2014

Mysql Interview Questions And Answers - Atomicity, Dedlock, Client Program, Mysql Mode, Mysql Sensitivity Of Identifiers And Mysql Errors

Question: what is the difference between where and having clause in mysql?
Answer: where can restrict each row or record
having clause restrict group of records.

Question: What is Atomicity?
Answer: This means whether execution of "all" statements or "no" statements.

Question: What is Deadlock?
Answer: A failure or inability to proceed due to two transactions having some data that the other needs.

Question: What is mysql client program ?
Answer: It is a command-line program that acts as a text-based front end for the MySQL Server. It's used for issuing queries and viewing the results in the terminal window.

mysql --help
mysql --version
mysql --V

In many cases, a given option has both a long and a short form. Long options consist of a word preceded by double dashes(e.g. --) whereas short options consist of a single letter preceded by a single dash(e.g. -).

Question: What is difference between Interactive Mode and Batch Mode of mysql client?
Answer: In Interactive modes, you put simple query to get the result, In this results is return in window.
In Batch Mode, you put your all the queries in sql file and run it from mysql client OR from scheduler job.

Question: What is difference between \g and \G?
Answer: Both are the statement terminator alike semicolon(;).
\g end the query statement and output the result in horizontal.
\G end the query statement and output the result in vertically and mainly used when output is large.

Question: How to manage MySQL case sensitivity of identifiers?
Answer: Database name and table name are stored as file, So In window its case-insenstive and in unix it is case senstive.
Column name, index, and trigger are not case sensitive.
Column aliases are not case sensitive

Question: What is difference between identifier-quoting- character and string-quoting-character?
Answer: backtick(`) are identifer quoting character and used quote for dbname, tableName and filedName
Single Quote('), Double Quote(") are string quoting character