How to Implement Multithreading in Ruby

In this article, we will learn how we can use multithreading in Ruby. We will take a couple of examples, where we will spawn two new threads and then perform some concurrent operations on them. In Ruby, we can create a new thread with the help of the Thread.new() function.

Example 1

Take a look at the following example to understand the nature of multiple threads and how they are executed in Ruby.

#!/usr/bin/ruby

# first method
def First_Method
   a = 0
   while a <= 5
      puts "Thread1: #{a}"

      # pause the execution of the current thread
      sleep(1)

      # incrementing the value of a
      a = a + 1
   end
end

# Second method
def Second_Method
   b = 0
   while b <= 3
      puts "Thread2: #{b}"

      # Pause the execution of the current thread
      sleep(0.5)

      # incrementing the value of b
      b = b + 1
   end
end

x = Thread.new{First_Method()}
y = Thread.new{Second_Method()}

# using Thread.join
x.join
y.join

puts "End"

Output

On execution, it will produce the following output

Tuts1: 0
Tuts2: 0
Tuts2: 1
Tuts1: 1
Tuts2: 2
Tuts2: 3
Tuts1: 2
Tuts1: 3
Tuts1: 4
Tuts1: 5
End

In this example, we looked at two threads and how context switching is happening between them.

Example 2

Now let's take a look at how we can define some logs in between the functions to show the scope of the threads. Consider the code shown below.

#!/usr/bin/ruby

$str = "Learn To Code in Ruby"

# first method
def First_Method
   a = 0
   while a <= 5
      puts "Thread1: #{a}"

      # pause the execution of the current thread
      sleep(1)

      # incrementing the value of a
      a = a + 1
   end

   puts "Global variable: #$str"
end

# Second method
def Second_Method
   b = 0
   while b <= 3
      puts "Thread2: #{b}"

      # pause the execution of the current thread
      sleep(0.5)

      # incrementing the value of b
      b = b + 1
   end

   puts "Global variable: #$str"
end

x = Thread.new{First_Method()}
y = Thread.new{Second_Method()}

# using Thread.join
x.join
y.join

puts "End"

Output

On execution, it will produce the following output

Thread1: 0
Thread2: 0
Thread2: 1
Thread1: 1
Thread2: 2
Thread2: 3
Thread1: 2
Global variable: Learn To Code in Ruby
Thread1: 3
Thread1: 4
Thread1: 5
Global variable: Learn To Code in Ruby
End