manjuraj

#include <stdlib.h>
#include <stddef.h>

/* 
 * C struct hack - the last member of the struct is of variable length
 *
 * C99 however introduces the concept of a flexible array member, which
 * allows the size of an array to be omitted if it is the last member
 * in a structure
 */

manjuraj

# Notes:
# List comprehension (listcomps) is an expression.
# With list comprehension, you get back a list, not a generator.
# With generator expression, you get back an iterator that computes values as an when needed.

# prints [1, 2, 3, 4]
[x for x in (1, 2, 3, 4)]

# prints [2, 4]
[x for x in (1, 2, 3, 4) if x % 2 == 0]

manjuraj

def gen(num):
    n = 0
    while n < num:
        yield n
        n += 1

# returns a generator object
g = gen(3)

# returns 0

manjuraj

items = [1, 2, 3]
it = iter(items)

# prints 1
print it.next()

# prints 2
print it.next()

# prints 3

manjuraj

L1 cache reference                  0.5 ns
Branch mispredict                   5 ns
L2 cache reference                  7 ns
Mutex lock/unlock                   25 ns
Main memory reference               100 ns
Compress 1K bytes with Zippy        3,000 ns
Send 2K bytes over 1 Gbps network   20,000 ns
Read 1 MB sequentially from memory  250,000 ns
Round trip within same datacenter   500,000 ns
Disk seek                           10,000,000 ns

manjuraj

branch = redis_unstable on github.com/twitter/twemproxy

## redis-benchmark through a local twemproxy (nutcracker)
$ ./redis-benchmark -q -p 22121
SET: 63291.14 requests per second
GET: 65359.48 requests per second
INCR: 64935.07 requests per second
LPUSH: 67114.09 requests per second
LPOP: 68493.15 requests per second
SADD: 66225.16 requests per second

manjuraj

IP Header = 20 TCP Header = 20 Ethernet = 20

Loopback RTT = 0.01 msec Datacenter RTT = 0.250 msec

1 Gbps = 128 MBps Assume 40% overhead, 600 Gps = 75 MBps

manjuraj

// my response to https://groups.google.com/forum/?fromgroups#!searchin/play-framework/cake/play-framework/LQ2y40QNZaE/qvRFw5of-rQJ

import play.api._
import play.api.mvc._

// Domain object
case class User(id: String, name: String)

// Trait defining the service component
trait UserServiceComponent {

manjuraj

// (1). Simplified - A Thing[A] to compute another Thing[B]
// Thing[A] is like a simplest posssible container for a value and the
// pattern, given a Thing[A], and a function flatMap, pulls a value of
// type A out of the Thing[A] and applies the function flatMap() on this
// value of type A and returns another new Thing[B] with a value of
// type B injected into it by the constructor (apply() method here)
// encapsulates a monad in loose sense
case class Thing[+A](value: A) {
  def flatMap[B](f: A => Thing[B]) = f(value)
}

manjuraj

// from: http://jonasboner.com/2008/10/06/real-world-scala-dependency-injection-di

// (1).

case class User(username: String, password: String)

trait UserRepositoryComponent {
  val userRepository: UserRepository

  class UserRepository {