Wednesday, August 12, 2015

Installing Kibana to work with multiple Elasticsearch clusters

Currently Kibana doesn't support querying ElasticSearch instances in different clusters. One workaround to this problem is using tribe nodes. The tribes feature allows a tribe node to act as a federated client across multiple clusters. (

In order to visualize data coming from different clusters in a Kibana instance we can configure it to talk to a tribe node which is connected to all the elastic search clusters. However tribe nodes can't have any data and Kibana requires certain indexes to store the information regarding dashboards & saved visualizations. This can be fixed by creating Kibana related index in any one of the cluster. 

Tribe Node configuration (With two clusters)

  • "x.x.x.a:9300","x.x.x.b:9300" and "x.x.x.c:9300" are part of cluster "x"
  • "x.x.x.d:9300" is part of cluster "y"

elasticsearch.yml for tribe node (Kibana should connect to this node)
    t1:   x false ["x.x.x.a:9300","x.x.x.b:9300","x.x.x.c:9300"]
    t2:   y false ["x.x.x.d:9300"]

Queries to be executed in one of the nodes in any cluster (To create Kibana specific indices and mappings)

curl 'http://x.x.x.a:9200/.kibana' --data-binary '{"settings":{"number_of_shards":1,"number_of_replicas":1}}' --compressed

curl 'http://x.x.x.a:9200/.kibana/_mapping/index-pattern' -X PUT 'Connection: keep-alive' --data-binary '{"index-pattern":{"properties":{"title":{"type":"string"},"timeFieldName":{"type":"string"},"intervalName":{"type":"string"},"customFormats":{"type":"string"},"fields":{"type":"string"}}}}' --compressed

curl 'http://x.x.x.a:9200/.kibana/_mapping/search' -X PUT --data-binary '{"search":{"properties":{"title":{"type":"string"},"description":{"type":"string"},"hits":{"type":"integer"},"columns":{"type":"string"},"sort":{"type":"string"},"version":{"type":"integer"},"kibanaSavedObjectMeta":{"properties":{"searchSourceJSON":{"type":"string"}}}}}}' --compressed

curl 'http://x.x.x.a:9200/.kibana/_mapping/visualization' -X PUT --data-binary '{"visualization":{"properties":{"title":{"type":"string"},"visState":{"type":"string"},"description":{"type":"string"},"savedSearchId":{"type":"string"},"version":{"type":"integer"},"kibanaSavedObjectMeta":{"properties":{"searchSourceJSON":{"type":"string"}}}}}}' --compressed

curl 'http://x.x.x.a:9200/.kibana/_mapping/dashboard' -X PUT --data-binary '{"dashboard":{"properties":{"title":{"type":"string"},"hits":{"type":"integer"},"description":{"type":"string"},"panelsJSON":{"type":"string"},"version":{"type":"integer"},"kibanaSavedObjectMeta":{"properties":{"searchSourceJSON":{"type":"string"}}}}}}' --compressed

Sunday, May 3, 2015

Common Computer Science and Information Technology B. Tech Projects

Project Title:
 Online Railway reservation management System

Project Abstract and brief report:
Application will allow users to view trains between two station, see seat availability, check fares and to book the ticket depending on availability. If you are doing it as a final year B. Tech. project then you can also include provision to choose your seat according to interest through an interactive user interface. Login module should allow only authenticated users to book the ticket, see booked ticket history and check status of booked tickets.

Other requirements for project: Analyse IRCTC website and find its flaws (I am sure you can find many if you are a regular student) try to include provisions that improve robustness. Make use of existing solutions related to distributed system that can allow the site to handle very large number of users at any instance.
Source code implantation languages: For implementation any server side scripting language such as php, asp or jsp can be used. You should make use of your HTML, CSS, javascript knowledge to make the system more interactive and user friendly.

Keywords: irctc, online reservation, online railways, railway management project, Indian railways

Related Projects / Downloads :, + you can find few projects for download by googling

Project Title: Employees management System

Project Abstract and brief report:
You can also call this project as universal employees management system or an Employees information system. Project will allow admin to add new employees after proper authentication. Admin can also add new departments and posts. It can allocate employees to different departments at different posts. Database should store all personal details of employees such as date of birth full name etc. and his educational background, work experience, skill sets, current and past projects in different tables with proper relations

Source code implantation languages: Concentrate in proper ER Diagrams, use MySQL or Oracle for database functionality  System can be coded in visual basic, java, php or jsp depending on whether you want an offline application or an online one.

Keywords: employees management system, employees information system, employee database project, software, web application, vb dot net, visual basic, java, c#, php

Related open source project downloads:
Employee Time management
Employee attendance management with import and reports
Employees Profile Viewer

Project Title: Library management System
Project Abstract and brief report:
Project should have different level of access for different types of users. It should allow library manager administrator to add new books in database under different categories. It can also add/delete/modify a category. System should integrate with existing student database and librarian should have proper access to issue a book to a particular student. Student can see issued books. Library management system should automatically send email and SMS to students who have not returned the book even after due date. System should have provision to calculate fine based on conditions set by the global administrator.

Source code implantation languages: Library management system can be coded in java or c# so as to give it look of standalone software. If you wish to include sms alerts feature then SMS gateway feature should be included. You can read more about sms gateways and their HTTP API’s in the same blog. I have written a complete blog post on SMS gateways and their operation.

Keywords: library management system, online books library project, library information management, books management system, intelligent application, database project

Related Open source Implementation Download

Project Title: Contact management System

Project Abstract and brief report:
An interactive application for managing contacts easily. There are thousands of contact management applications coded in different languages such as vb dot net, java, php, jsp, asp etc. for variety of platforms such as desktop computer, android mobiles, windows phone, iOS etc. This application should stand out among all these apps in a way that it can be opened in any device. It should allow user to add new/modify/delete contacts. It should sync contacts with google, facebook and other popular networks. Application should allow user to export contacts in printable format if required. User should be able to query information as easily as possible.  

Source code implantation languages: Since portability is the main criteria here therefore it is advised that the system should be coded as a web application using latest technologies such as HTML5, CSS3, javascript. Make use of responsive web designing for making the app universal. Use PHP, JSP ar any other server side scripting language for database connectivity and processing

Keywords: contact management system, html5 project, php project, web application, responsive

Related Projects and Source code downloads:

Latest subjective C questions asked in placement interviews

Comment on the output of following C code:
 #include <stdio.h>  
 int main(){  
  const int x=10;  
  int *p;  
  printf("%d %d",*p, x);  
  return 0;  

Answer: We are trying to change the value of a const variable. Such code may lead to unknown behaviour in program depending on compiler used. In Dev C++ code compiles with warning and produces output 20 20. Thus value of a constant is being changed through pointers. Such error can be prevented if we make use of pointer to constant to store the address of x instead of a simple integer pointer. If we use int const *p=&x; then *p=20 will produce a compilation error.

Question: What is output of following code snippets

c interview question 51

printf("a%d%d%d"+2,1,2); //Q

Answer & Explanation

P : tandon
+1 removes 1 char from format specifier string.
Q: d12

+2 will remove 'a' and first % from format specifiers, remaining %d will be replaced by corresponding values => d12

c interviewQuestion: Explain #ifndef. Is there any alternative to it?

Answer: #ifndef is used to execute a piece of c code if particular macro is not defined.
#ifndef RSA

<code written here will execute only if we have defined constant RSA as #define RSA {some value}>


We can also use

#if !defined(RSA) instead of #ifndef RSA

Question: What is the use of # in macro functions?

Answer: It is used to return the string equivalent of the passed parameter. Consider the following example:-
#define debug(exp) printf(#exp " =%f",exp);

Now debug(x/y); will convert to printf("x/y" " =%f",x/y);

This will print: x/y =<value of x/y in float>

Question: Explain use of ‘##’ in macros.

let's say you have
c interview
#define dumb_macro(a,b) a ## b
Now if you call the above macro as dumb_macro(hello, world)
It would result in
which is not a string, but a symbol(token) and you'll probably end up with an undefined symbol error saying
'helloworld' doesn't exist unless you define it first. To make this legal you first need to declare the symbol like this.

int helloworld;
dumb_macro(hello, world) = 3;
printf ("helloworld = %d\n", helloworld); // <-- would print 'helloworld = 3'

## is called token passing argument since it is used to create tokens through passed arguments

Question: Find output of following code snippet in C++
c questions

#include <iostream>
#include <conio.h>
using namespace std;
int foo1(){
     cout<<"foo1 ";  
     return 1; 
int foo2(void* a, void* b){
    cout<<"foo2 ";
    return 2;
int main(){
        int x=~foo1()&~foo2(cout<<"a ",cout<<"b ");//foo1 b a foo2

foo1 b a foo2

Explanation: << operator associated with cout object returns a reference to itself this can be accepted by void* (generic pointer) ~ is negation operator. The output depends on order of execution of expression and order in which parameters are passed in function.

Question: What value is returned by cout<<"Hello";
c interview

Answer: cout is an object to represent standard output stream. << operator associated with it returns a reference to same standard output stream object. This allows chaining of << operators and thus

cout<<"hello"<<" world";

is same as cout<<"hello world";

c questionQuestion: Which library function will you use to convert a string to equivalent integer?
Answer: int atoi(const char*)

Write a c program to implement your own version of above function?
Answer: Refer
The C Programming Language, second edition,
by Brian Kernighan and Dennis Ritchie

Question: What is fall through? How is it useful? 
c question

Answer: Flow of control to following cases after the matching case in absence of break statement after the matching case is known as fall through.
Fall-through allows multiple labels to be associated with a single action.

Question: What is the significance of break statement after default?

Answer: Fall through can occur after default too. If default is not the last label and there are other labels after it without any break in between. Therefore as a defensive programming you may add a break after default too although it is logically unnecessary.

Find output of following code:
#include <stdio.h>
    printf ("%*d\n", 10, 20);     // P
    printf ("%*d\n", 20, 10);     // Q

In P, 10 is substituted in place of * and it indicates putting the value 20 in 10 columns.

In Q, 20 is substituted for * and it indicates putting the value 10 in 20 columns.

Question: What is the use of volatile keyword in C Language?

c with AbhasBy declaring a variable as volatile in C we instruct the compiler that the value of that variable can be changed by means outside the code such as hardware or other program. It is important to note that volatile variables can be constants (declared const) if this code is not allowed to change its value. If we declare a variable as volatile then every time such variable is encountered in the code compiler fetches its value from memory instead of using any optimizations. This ensures that we are reading the correct value of such variable. Volatile memory access is required in case of files which can be read my multiple programs simultaneously.  

c questions answers
Question: What is difference between a character stored in a char variable eg. char ch='x' and a simple character constant ‘x’?

Look at the following code

    char b = 'c';
    printf("size of char constant %d\n", (int)sizeof('a'));
    printf("size of char variable %d",(int)sizeof(b));

size of char constant 4
size of char constant 1

Explanation: According to the ANSI/ISO 99 C standard, the expression 'a' starts with type int. If you have a function void f(int) and a variable char c, then f(c) will perform integral promotion, but f('a') won't because the type of 'a' is already int.

Question: What is the significance of value returned by main in C?

c interview
Answer: It tells the environment about the status of program execution. 0 signifies normal termination and non-zero value tells some error in execution. The value returned can be displayed using echo %errorlevel% in Windows and echo $? in UNIX.

Question: In JAVA main function doesn't return any value so how can you tell the environment about the status of program execution? 

Answer:  We can use System.exit(0); or System.exit(<non-zero error code as integer>);

c interview

Question: getchar() is a library function to input a character from console. What data type you should use to store the value returned by this function?

Answer: int !!!

Explanation: EOF is an integer constant defined in stdio.h while reading characters using getchar() EOF is returned instead of ASCII value of the character when no more characters are available. Therefore we must read the input from getchar() in an integer and not char directly so that the variable is big enough to read the EOF value.

c interview
Question: If we have given a pre-processor directive in a c program as "#define <name> <replacement-text>", every occurrence of <name> in program will be replaced by the corresponding <replacement-text>

Answer: False

Explanation: Replacements won't be made when <name> occurs as part of other name Eg. <prefix-name> also replacements won't be made if <name> occurs inside quotes.

c questions
Question: What is the output for following code snippet?

float d=22.44;

Answer: %X.Yf prints a float value right justified in X columns up to 1 digit after decimal. Minus can be used in format specifier to make the text left justified. Thus the code tells to print 22.44 as 22.4 left justified in a column whose width is eight.

c interview questions answers
Question: What are the input and output functions defined in C language?

Answer: There is no input or output function defined in c language. printf & scanf are parts of standard input output library that is normally accessible to a c program. The behaviour of standard input output functions are defined in ANSI standard and its properties should be same in any compiler that follows the standards.

Question: Find the output of following snippet

#include <stdio.h>
int main(){
   int c,f=100;
   c=5/9*(f-32); //A



Explanation: In c automatic truncation to integer is done for int data type variables. On using float/double constant same can be prevented with the help of automatic type promotion.

Saturday, February 14, 2015

Happy Valentine's Day :)

In this great day, all of you should pause for a moment and be grateful to the one who made Valentine's day possible.

No, no and NOO. I am not talking about some Saint Valentine of Rome who was imprisoned and executed for performing weddings for soldiers who were forbidden to marry. He obviously is important to valentine's day, but the real credit to make this day possible goes to (as you might have already guessed) Eukaryotes.

For those who don't know, Eukaryotes were the first complex life form to appear on our tiny blue planet nearly 2 billion years ago. But they didn't stop there, unlike their distant ancestors 'Prokaryotes' which originated 3.6 billion years ago and were simple cell forms of life and primarily spend all their lives in water doing photosynthesis and asexual reproduction and created enough oxygen to make origin of Eukaryotes possible.

By this time, you would have already guessed, Yes !! Eukaryotes were the first to start heterosexual reproduction which ultimately lead to celebration of Valentine's day after roughly 1.2 billion years after a long chain of evolution and mass destruction that wiped off several species and allowed Homo sapiens to develop into (what some  believe) socially aware intelligent life form.

Also, it is very important to note that since we all evolved from same Eukaryotes, there is a good probability that that little bacteria on the pizza which you ate last week was your distant cousin. Same is true for the chicken you will eat tonight and the mosquito which you killed yesterday while it was sucking your blood. So I will end this long message on this happy note and once again Happy Valentine's day to all.

Tuesday, January 13, 2015

We have three binary palindrome dates in 2015 !!

Hey number lovers believe it or not 2015 is a special year. What happens in January may repeat in December !!! Why ??? Because 2015 is 111101111 in binary. Yes, it's a palindrome. In fact 2015 is the last Binary Palindrome Year we’ll Have Until 2047

And this doesn't end here. We have three binary palindrome dates (in ddmmyy) this year. Sad part is we have already missed one of them :(

They are:- Mon Jan 05 2015, Tue Mar 10 2015 Sun Jun 21 2015 And here's a jsfiddle and js code to prove this :D

 function isPalindromeDate(date) {  
   return Number(date.getDate() + "" + date.getMonth() + "" + date.getYear()).toString(2).split("").reverse().join("") == Number(date.getDate() + "" + date.getMonth() + "" + date.getYear()).toString(2);  
 var date = new Date("01/01/2015");  
 var i;  
 for (i = 0; i &lt; 365; i++) {  
   date.setDate(date.getDate() + 1);  
   if (isPalindromeDate(date)) {  
     document.querySelector("body").innerHTML +="Yuureekaa !!!: " + date + " - is a binary palindrome in ddmmyyyy   

Feel free to use the above functions to find out if any of you have a binary palindrome birthday. Do let me know if you find one cos I don't have one :(  :D

Thursday, October 3, 2013

10 C Interview Questions and Answers

c interview questions and answers
In this post you can find 10 Latest c interview questions and answers. These are some of the best c language questions asked  to freshers in technical interviews. I have tried to provide answers with full explanation. If you are looking for simple c questions then you can have look at my previous posts. You may ask all your doubts by commenting in the post. I'll try my best to answer your questions at earliest.

C Placement questions answers for beginners

Question 53. Compare arrays and pointers {Give both similarities and difference}.

Answer: Array is nothing but a pointer in disguise. Array name stores base address of array. Thus we can say array points to a memory location of fixed size of a particular data type.
arr[1] is same as *(arr+1)
{In fact 1[arr] is same as arr[1] because they both are converted into *(1+arr) and *(arr+1)}
However array is not same as pointer. We may make a pointer point to an arbitrary location however an array always points to a constant memory location.
int a[5]={1,2,3,4,5};
int *p=a;
=>p=&a[2]; or p++; are both correct but similar statements for array 'a' will invoke error.

C Pointer placement question answer with explanation

Question 54. Find output of C snippet given below (Assume address of variable ‘a’ is 100):

int main(){
  int a=5;
  int *p=&a;
  int x=(*p)++;// P
 printf("%d %d %u ",a,x,p);
  x=*p++; //Q
  printf("%d %d %u",a,x,p);

6 5 100
6 6 104

P: Increments a by one and stores old value in x => x=5 a incremented to 6
Q: This will make pointer move ahead and give value at the location pointed by it previously =>x=6, a remains 6

Advanced c programming question answer on strings

 Question 55. Explain the difference between a character array and a character pointer.

int main(){
    char *cp = "Hello world";//Character pointer
    //will place Hello world in the read-only parts of the memory
    //and making cp a pointer to that, making any writing operation on this memory illegal. While doing:
    //*(cp+1)='a'; is runtime error
    char s[] = "Hello world";//array of characters
    //puts the literal string in read-only memory and copies the string to newly allocated memory on the stack.
    s[0] = 'J';//correct

Tricky C Interview question on dangling pointers

Question 56. Find output of following C code:

char *getString()
    char str[] = "Will I be printed?";   
    return str;
int main()
    printf("%s", getString());

Output: Some garbage value
(PS:On running in Dev C++ I am getting warning in compilation "Function returns address of local variable" and no output)
The above program doesn't work because array variables are stored in Stack Section and have a definite lifetime. So, when getString returns, value at str are deleted and str becomes <dangling pointer>.

C Interview question on library function

Question 57. C library function to find the data type of variable


int main(){
    int a=2;
    typeof(a) b=1;
    printf("%d %d",a,b);//2 1

C Tricky interview question with answer and explanation

Question 58

void change()
  // Add a statement here such that printf in main prints 5

int main()
int i;
printf("%d",i); /* this should print 5*/


#define printf(x,y) printf("5")
You can use macro to change the default behaviour of library functions as well.

C interview question answer on pointer to function

 Question 59. Find Output of following code:

int fun(int a){
    printf("In fun %d\n",a);
    return a+1;
int fun2(int a){
    printf("In fun %d\n",a);
    return a-1;

int main(){
    int (*ptr)(int);
    int x=(*ptr)(3);
    printf("In main %d\n",x);
    printf("In main %d\n",x);

In main 4
In main 2

C Interview question on structure

Question 60. Find output of following C code

int main(){
 struct test{
    char a;
    int b;   

Answer: Size might be 8 and not 5 as expected

Explanation: Size of structure might NOT be sum of size of its elements. It is large enough to hold all the members. There might be unnamed holes in memory due to alignment requirements.

C placement question answer for technical interviews

 Question 61. Find output of following code:

short func(short x) { 
   printf(“Hello World");    // P
   return x;

int main() {
   printf("%d", sizeof(func(3)));
   return 0;

P: This statement is not executed since fun() is not called.
sizeof is a compile time operator. Operand is evaluated only if it is a variable length array. In above case all that matters to sizeof is the return type of the function.

C Interview question answer on structure pointer

Question 62. Find output of following C code
struct a{
   int b;
   int c;
   int d;
int main(){
    struct a *p=&i;
    printf("%d %d ",*p);

7 2
If we change the printf statement to printf("%d %d %d",*p); then 7 2 3 is displayed

Sunday, September 15, 2013

C Debugging Interview question

Find output of following code:

c interview questionsint main(){
    register int a=5;
    int *rp=&a;
    int **rpp=&rp

Answer: Error
Explanation: We can’t request address of a register variable. It is illegal to apply & operator to a variable declared as a register.

Basic C interview questions for Mass companies like Accenture, TCS, Infosys & Wipro

In this post freshers seeking job in IT sector can find some basic definitions related to c language. Such definitions are usually asked by companies such as TCS, CTS, Infosys, Accenture and Wipro during mass recruitment.

C Interview questions answers

Collection of Simple C Interview Questions: 

#1 Variable: named memory location used to store value of particular data type.
#2 Data type: Means to identify the type of data. Eg. int, float, char
#3 Pointers: A special type of variable that stores address of another variable.
#4 Compound Statement: Group of statements enclosed in {}
#5 Identifier: Names given by programmer to various parts of program. Eg. In int a=5; ‘a’ is an identifier.
#6 Token: Smallest individual unit of a program. Eg. variable, constants.
#7 function: Group of statements used to perform a particular task. It may or may not accept parameters and may or may not return a value. They help in code re-usability.
#8 Keyword: Words which convey special meaning to compiler. Eg. for, int, while etc.
#9 Recursion: When a function calls itself.
#10 Array: Collection of similar data type stored in contiguous memory location.
#11 structure: Collection of data of any data type stored in contiguous memory space.
#12 String: Array of character.

Other simple C language questions asked in mass companies:

#13 Difference between = and == operator
#14 Differences between C and C++
#15 Difference between for(), while and do while loops.
#16 Types of storage class in C (auto, register, extern and static)
#17 Program to reverse a number
#18 C program to swap numbers with and without temporary variable.
#19 Difference between structure and union.
#20 What is typedef.
#21 What is void pointer.
#22 What is null pointer.
#23 Differences between actual parameter and formal parameter.
#24 What is a function definition?
#25 What is a function signature?
#26 Differentiate between call by address and call by value.
#27 Differentiate between switch and if statement.
#28 Difference between malloc() and calloc()
#29 C Program to print factorial of a number.
#30 C Program to find sum of matrix
#31 C sorting programs: bubble, insertion and selection
#32 C code for linear and binary search

#33 What are type casting and type promotion?

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