Happytreat

# Credits to https://pdos.csail.mit.edu/6.824/notes/l-memcached.txt

k not in cache
C1 get(k), misses
C1 v1 = read k from DB
  C2 writes k = v2 in DB
  C2 delete(k)
C1 set(k, v1)
now mc has stale data, delete(k) has already happened
will stay stale indefinitely, until k is next written

Happytreat

# Install libevent needed for memaslap
sudo apt-get install libevent-dev

cd libmemcached-1.0.18
 
 
# Edit Makefile by adding LDFLAGS "-L/lib64 -lpthread"
# https://bugs.launchpad.net/libmemcached/+bug/1562677
### diff of Makefile
# -LDFLAGS =

Happytreat

// condRelease releases this connection if the error pointed to by err
// is nil (not an error) or is predefined Reusable error
// The purpose is to not recycle TCP connections that are bad.
func (cn *conn) ConnRelease(err *error) {
	if *err == nil || resumableError(*err) {
		cn.release()
	} else {
		cn.nc.Close()
	}
}

Happytreat

type ConnectionOptions struct {
	// The initial num of active connections when pool is initialised
	// Pros: Warmup the connection pool with some connections on startup. 
	InitialActiveConnections int

	// The maximum number of connections that can be active at any given 
	// time
	MaxActiveConnections int

	// The maximum number of idle connections per host that are kept alive by

Happytreat

type ConnectionPool interface {
	// This gets an active connection from the connection pool if exists,
        // else create a new connection. 
	Get() (net.Conn, error)

	// This releases an active connection back to the connection pool.
	Release(conn net.Conn) error

	// This discards an active connection from the connection pool and
        // closes the connection.

Happytreat

/** 
* Adapted Example from: Protocol-oriented Programming in Swift - WWDC 2015 
* https://developer.apple.com/videos/play/wwdc2015/408/
*/

/** 
* Without Self (protocol or class implementation)
* sortedKeys is a heterogeneous array of Ordered objects which could contain both Number and Label objects
*
* This implementation will raise an error if Self is being used: 

Happytreat

/** 
* Example from: Protocol-oriented Programming in Swift - WWDC 2015 
* https://developer.apple.com/videos/play/wwdc2015/408/
*/
protocol Ordered {
  func precedes(other: Self) -> Bool
}

// value type struct
struct Number: Ordered {

Happytreat

/** 
* Example from: Protocol-oriented Programming in Swift - WWDC 2015 
* https://developer.apple.com/videos/play/wwdc2015/408/
*/
class Ordered {
  func precedes(other: Ordered) -> Bool { fatalError("implement me!") }
}

class Label : Ordered { var textL String = "" ... }

Happytreat

/** 
 * Example from Protocol Oriented Programming - Advanced Swift Programming - raywenderlich.com 
 * https://www.youtube.com/watch?v=ekYdBcl3dzs
 */

protocol Geometry {
  var size: CGSize { get } 
  func boundingBoxArea() -> CGFloat // area -> boundingBoxArea
}

Happytreat

/** 
 * Adapted Example from Protocol Oriented Programming - Advanced Swift Programming - raywenderlich.com 
 * https://www.youtube.com/watch?v=ekYdBcl3dzs
 */

// Base class for inheritance
class Shape {
  var size: CGSize
  func draw(on context: CGContext) { fatalError("override \(#function)") }
  func area() -> CGFloat { return size.width * size.height }