cfc1020

Sessions and Conversations

HTTP is a stateless protocol. Sessions allow us to chain multiple requests together into a conversation between client and server.

Sessions should be an option of last resort. If there's no where else that the data can possibly go to achieve the desired functionality, only then should it be stored in the session. Sessions can be vulnerable to security threats from third parties, malicious users, and can cause scaling problems.

That doesn't mean we can't use sessions, but we should only use them where necessary.

Adding, Accessing, and Removing Data

cfc1020

# Manually secure port 6379
sudo iptables -A INPUT -p tcp --dport 6379 -s xxx.xxx.xxx.xxx -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 6379 -j DROP
sudo iptables -L

# Save current firewall config
sudo iptables-save > /etc/iptables.conf

# Load iptables.conf on startup
sudo nano /etc/rc.local

cfc1020

require 'benchmark'

examples = []

res1 = []
res2 = []

def f1(arr, k)
  arr.sort[arr.size - k]
end

cfc1020

// Given an array of integers, A of length N, find out the maximum sum sub-array of non negative numbers from A.
/**
 * @input A : Integer array
 * 
 * @Output Integer array.
 */
package main

import "fmt"

cfc1020

class MySolution
    # @param a : string
    # @param b : string
    # @returns an integer
    def compare_versions(a, b)
        aa = a.split('.')
        bb = b.split('.')
        
        i = 0

cfc1020

# @param {Integer} n
# @return {String}
def convert_to_title(n)
    res = ''
  
    begin
      rem = n % 26
      n /= 26
      
      rem = if rem.zero?

cfc1020

# @param {Integer} n
# @return {Integer}
def binary_gap(n)
  res = 0
  
  while n.nonzero? do
    n &= n << 1
    
    res += 1
  end

cfc1020

# @param {String} address
# @return {String}
def defang_i_paddr(address)
  address.split('.').join('[.]')
end

cfc1020

# Definition for a binary tree node.
# class TreeNode
#     attr_accessor :val, :left, :right
#     def initialize(val = 0, left = nil, right = nil)
#         @val = val
#         @left = left
#         @right = right
#     end
# end
# @param {TreeNode} root

cfc1020

# @param {String} s
# @return {Integer}
def min_add_to_make_valid(s)
  res     = 0
  balance = 0

  s.each_char do |c|
    balance +=  c == '(' ? 1 : -1

    if balance < 0