Word Boundaries Regex

\b

This is the second time this week where I have had to ask myself "how did I not know about this?"

There is a regex character to identify word boundaries: \b This is a zero length match, similar to the caret and dollar sign. It finds the boundaries between words, allowing you to search for a whole word match.

Below is a sample extension method that uses this to replace words in a string.

Implementation

public static class StringExtensions

{

    private static readonly Regex WordRegex = new Regex(@"\b\w+\b", RegexOptions.Compiled);

    public static string ReplaceWords(

        this string input,

        string find,

        string replace,

        StringComparison comparison = StringComparison.InvariantCulture)

    {

        return WordRegex.Replace(input, m => m.Value.Equals(find, comparison)

            ? replace

            : m.Value);

    }

}

Common Logging Extensions with Caller Information

Update: Added the BreakParameter.

I have made it an (arguably bad) habit of manually adding the class and method name as a prefix to all my log lines. It is not that I enjoy typing out the same strings over and over, it's that I do not always trust things like the NLog callsite. Using the stack frame to identify a calling method always requires a bit of cleverness on the part of the author, as you never can be totally sure when you are dealing with a wrapper class or an async call stack.

I was recently introduced to the Caller Information attributes in C# 5, and now I think I am in love.

Disclaimer: I have not used this very much yet, but I intend to start! I think that these attributes are absolutely brilliant in their simplicity: a compiler trick to insert debug information directly into your code. That is freak'n sweet, and it's performant! I am not sure how this flew under my radar, but now that I know about it....

Below is a little T4 template that I wrote up to generate overloads for Common Logging that will include caller information. To customize this for your needs, just update the the GetFormat method at the bottom of the template.

Unit Tests

   1:  using System;

   2:  using System.Collections.Generic;

   3:  using Common.Logging.Simple;

   4:  using Xunit;

   5:   

   6:  namespace Common.Logging.Tests

   7:  {

   8:      /// <summary>

   9:      /// Tests for Common Logging extensions that use Caller Information

  10:      /// https://msdn.microsoft.com/en-us/library/mt653988.aspx

  11:      /// </summary>

  12:      public class LogCallTests

  13:      {

  14:          [Fact]

  15:          public void LogFromMethod()

  16:          {

  17:              var log = new QueueSimpleLogger();

  18:              var ex = new Exception("Boom");

  19:   

  20:              log.Debug("Hello");

  21:              log.Debug("World", ex);

  22:   

  23:              log.DebugCall("Hello");

  24:              log.DebugCall("World", ex);

  25:   

  26:              log.WarnFormat("Hello - {0}", "Zero");

  27:              log.WarnFormat("World - {0}", ex, "Zero");

  28:   

  29:              log.WarnFormatCall("Hello - {0}", "Zero");

  30:              log.WarnFormatCall("World - {0}", ex, "Zero");

  31:   

  32:              Assert.Equal(8, log.Queue.Count);

  33:   

  34:              Assert.Equal("Hello", log.Queue.Dequeue());

  35:              Assert.Equal("World - Ex: Boom", log.Queue.Dequeue());

  36:   

  37:              Assert.Equal("LogCallTests.LogFromMethod(23) - Hello", log.Queue.Dequeue());

  38:              Assert.Equal("LogCallTests.LogFromMethod(24) - World - Ex: Boom", log.Queue.Dequeue());

  39:   

  40:              Assert.Equal("Hello - Zero", log.Queue.Dequeue());

  41:              Assert.Equal("World - Zero - Ex: Boom", log.Queue.Dequeue());

  42:   

  43:              Assert.Equal("LogCallTests.LogFromMethod(29) - Hello - Zero", log.Queue.Dequeue());

  44:              Assert.Equal("LogCallTests.LogFromMethod(30) - World - Zero - Ex: Boom", log.Queue.Dequeue());

  45:          }

  46:   

  47:          [Fact]

  48:          public void LogFromAction()

  49:          {

  50:              var log = new QueueSimpleLogger();

  51:              var ex = new Exception("Boom");

  52:              Action action = () =>

  53:              {

  54:                  log.Debug("Hello");

  55:                  log.Debug("World", ex);

  56:   

  57:                  log.DebugCall("Hello");

  58:                  log.DebugCall("World", ex);

  59:   

  60:                  log.WarnFormat("Hello - {0}", "Zero");

  61:                  log.WarnFormat("World - {0}", ex, "Zero");

  62:   

  63:                  log.WarnFormatCall("Hello - {0}", "Zero");

  64:                  log.WarnFormatCall("World - {0}", ex, "Zero");

  65:              };

  66:   

  67:              action();

  68:   

  69:              Assert.Equal(8, log.Queue.Count);

  70:   

  71:              Assert.Equal("Hello", log.Queue.Dequeue());

  72:              Assert.Equal("World - Ex: Boom", log.Queue.Dequeue());

  73:   

  74:              Assert.Equal("LogCallTests.LogFromAction(57) - Hello", log.Queue.Dequeue());

  75:              Assert.Equal("LogCallTests.LogFromAction(58) - World - Ex: Boom", log.Queue.Dequeue());

  76:   

  77:              Assert.Equal("Hello - Zero", log.Queue.Dequeue());

  78:              Assert.Equal("World - Zero - Ex: Boom", log.Queue.Dequeue());

  79:   

  80:              Assert.Equal("LogCallTests.LogFromAction(63) - Hello - Zero", log.Queue.Dequeue());

  81:              Assert.Equal("LogCallTests.LogFromAction(64) - World - Zero - Ex: Boom", log.Queue.Dequeue());

  82:          }

  83:   

  84:          private class QueueSimpleLogger : AbstractSimpleLogger

  85:          {

  86:              public readonly Queue<string> Queue = new Queue<string>(); 

  87:   

  88:              public QueueSimpleLogger()

  89:                  : base(string.Empty, LogLevel.All, true, true, true, string.Empty)

  90:              {

  91:              }

  92:   

  93:              protected override void WriteInternal(LogLevel level, object message, Exception exception)

  94:              {

  95:                  var s = message.ToString();

  96:                  if (exception != null) s += " - Ex: " + exception.Message;

  97:                  Queue.Enqueue(s);

  98:              }

  99:          }

 100:      }

 101:  }

IResourceLoader: Balancing Semaphores

Recently I need to get balance getting resources from a restricted number of sources. So, for example...

I am getting resource R, and I have factories A, B and C creating those Rs. Each of those factories has a very limited capacity for creating those resources, and can only create two Rs at a time. It is easy to put the factories behind a semaphore and limit how many threads can be requesting resources from each factory at a time.

The challenge is evenly balancing the workload between all three factories. Also, please note that you can't just round robin the semaphores because there is no way to ensure that each operation will complete in the same amount of time.

To do this I created a generic IResourceLoader interface, and made two implementations: one to wrap a semaphore, and the other to wrap and balance a collection of IResourceLoaders. Below is the implementation, complete with unit tests; let's take a look!

Interface

public interface IResourceLoader<T>

{

    int Available { get; }

    int Count { get; }

    int MaxConcurrency { get; }

    Task<T> GetAsync(CancellationToken cancelToken = default(CancellationToken));

    bool TryGet(out Task<T> resource, CancellationToken cancelToken = default(CancellationToken));

}