craigtp

Advanced Distributed System Design Course - Udi Dahan

Notes by Craig Phillips

Fallacies of Distributed Computing

• There are 11 fallacies of Distributed Computing:
  1. The network is reliable
  2. Latency isn’t a problem
  3. Bandwidth isn’t a problem
  4. The network is secure

5. The topology won’t change

craigtp

Option Explicit 

Dim objshell,path,DigitalID, Result 
Set objshell = CreateObject("WScript.Shell")
'Set registry key path
Path = "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\"
'Registry key value
DigitalID = objshell.RegRead(Path & "DigitalProductId")
Dim ProductName,ProductID,ProductKey,ProductData
'Get ProductName, ProductID, ProductKey

craigtp

-- Create a temporary table in an in-memory variable simply to allow the
-- select statement to output multiple rows.
DECLARE @TestTable TABLE (uniqueID int)
INSERT INTO @TestTable
SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL
SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 UNION ALL SELECT 10

-- The main Select statement that shows different correct (and incorrect) ways to generate
-- "random" things in a set-based select statement.
SELECT

craigtp

SELECT DB_NAME(database_id) AS DatabaseName,
Name AS Logical_Name,
Physical_Name, (size*8)/1024 SizeMB
FROM sys.master_files
ORDER BY SizeMB DESC

craigtp

(dir -include *.cs -recurse | select-string .).Count

craigtp

# Run this as Administrator
net stop w3svc
Get-ChildItem "C:\Windows\Microsoft.NET\Framework*\v*\Temporary ASP.NET Files" -Recurse | Remove-Item -Recurse -Force
net start w3svc

craigtp

using System;

namespace ShortCodes
{
    public static class ShortCodes
    {
        // You may change the "shortcode_Keyspace" variable to contain as many or as few characters as you
        // please.  The more characters that are included in the "shortcode_Keyspace" constant, the shorter
        // the codes you can produce for a given long.
        private static string shortcodeKeyspace = "abcdefghijklmnopqrstuvwxyz0123456789";

craigtp

OK so now you have implemented the kata. Your tests should look something like this:

We can say that the tests define the object "in a calculus of itself".
They are not state based tests, they define how the behaviours of the object interact with each other.

To see the real value of this let's introduce some change ... I hear real system's do this occasionally.
Because this is a high performance system decimal math is too slow. You now need to use floats instead. 

Need help on floating point math? Check out: http://www-users.math.umd.edu/~jkolesar/mait613/floating_point_math.pdf

craigtp

Value objects are an important concept in DDD. This kata is made both to learn value objects and to learn better ways of testing.

Write a probability value object. It should contain the following methods:
   Probability CombinedWith(Probability)
   Probability InverseOf()
   Probability Either(Probability)

if you forget your probability math:
   Either:P(A) + P(B) - P(A)P(B)
   CombinedWith: P(A)P(B)

craigtp

using System;
using System.Security.Cryptography;

namespace BetterRandomNumbers
{
	// BetterRandom.cs
	// This class implements a random number generator that is based off the Windows "Next Generation" cryptographically secure
	// random number generator.  It inherits from the base Random class, so can be used as a "drop-in" replacement for the
	// built-in .NET System.Security.Random class, but providing a superior quality of random numbers.
    public class BetterRandom : Random, IDisposable