Category Archives: Useful tools

Instrumentation presentation at Campus Days 2013

Campus Days 2013 logoI was fun to present today at Campus Days 2013 in Copenhagen, Denmark. The talk was about how to instrument software by using frameworks like TraceSource, EventSource, Event Tracing for Windows and how to perform post-mortem debugging via Visual Studio and PerfView.

Here is a great resource for enabling diagnostics in Azure.

Automatic Retry and Circuit Breaker made easy

Polly library logoIf you do not know Polly, you are missing out! I did not know about it until a couple of days ago and you properly never heard about it either, as this wonderful little library only has 63 downloads on NuGet at the time of writing.

Polly is an easy to use retry and circuit breaker pattern implementation for .Net – let me show you.
Start by specifying the policy – what should happen when an exception thrown:

  var policy = Policy
    .Handle<SqlException(e => e.Number == 1205) // Handling deadlock victim
    .Or<OtherException>()
    .Retry(3, (exception, retyCount, context) =>
    {
      // Log...
    });

The above policy specifies a SqlExeption with number 1205 or OtherException should be retried three times – if it still fails log and bobble the original exception up the call stack.

  var result = policy.Execute(() => FetchData(p1, p2));

It is also possible to specify the time between retries – e.g. exponential back off:

  var policy = Policy
    .Handle<MyException>()
    .WaitAndRetry(5, retryAttempt =>
      TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)
    );

Or the circuit breaker safeguarding against the same error occurs again and again if an external system is temporarily unavailable:

  var policy = Policy
    .Handle<TimeoutException>()
    .CircuitBreaker(2, TimeSpan.FromMinutes(1));

Go get it – I’m already using it :)

Check for breaking changes in APIs

Have you ever had the need to compare interfaces of two versions of the same framework?

If you have, then ApiChange is a tool for you. It’s open source, powerful and easy to use :-)

I gave it a spin comparing current trunk version 2.9.2 of Lucene.Net with the latest official release version 2.4.0.

I downloaded ApiChange and ran the following command in a command prompt:

ApiChange.exe -Diff -old C:\Lucene.Net_2_4_0\Lucene.Net.dll -new C:\trunk\Lucene.Net.dll

The output lists all the differences, but here is a summary:

  • 23 public types where removed
  • 96 public types where added
  • 158 public types where changed

Cool little tool with other features such as:

  • Diff public types for breaking changes.
  • Who uses a method?
  • Who uses a type?
  • Who uses implements an interface?
  • Who references me?
  • What format has the binary (32/64, Managed C++, Pure IL, Unmanaged)?
  • Search for all event subscribers and unsubscribers.

It’s based on Mono Cecil – a free IL parser, and not reflection as I initial thought. Go check it out…

Finding Missing Indexes with SQL Server DMVs

Finding Missing Indexes with DMVsSome time ago I wrote written about easy index wins for SQL Server 2005.

SQL server maintains statistics about indexes you should consider creating. This time I’ll show you a DMV (Dynamic Management View) that lists index candidates. This method works for SQL Server 2005 SP2 and later versions.

The query is based on three DMVs and returns index candidates where the calculated improvement is more than 10%:

SELECT
  migs.avg_total_user_cost * (migs.avg_user_impact / 100.0) * (migs.user_seeks + migs.user_scans) AS improvement_measure_pct,
  QUOTENAME(db_name(mid.database_id)) AS [database],
  QUOTENAME(OBJECT_SCHEMA_NAME(mid.object_id, mid.database_id)) AS [schema],
  QUOTENAME(OBJECT_NAME(mid.object_id, mid.database_id)) AS [table],
  'CREATE INDEX [missing_index_' + CONVERT(varchar(64), NEWID()) + ']'
  + ' ON ' + mid.statement
  + ' (' + ISNULL (mid.equality_columns, '')
  + CASE
      WHEN mid.equality_columns IS NOT NULL
	    AND mid.inequality_columns IS NOT NULL THEN ','
      ELSE ''
    END
  + ISNULL(mid.inequality_columns, '')
  + ')'
  + ISNULL(' INCLUDE (' + mid.included_columns + ')', '')
	  AS create_index_statement,
  migs.*,
  mid.database_id,
  mid.[object_id]
FROM sys.dm_db_missing_index_groups mig
  INNER JOIN sys.dm_db_missing_index_group_stats migs
	ON migs.group_handle = mig.index_group_handle
  INNER JOIN sys.dm_db_missing_index_details mid
	ON mig.index_handle = mid.index_handle
WHERE
	migs.avg_total_user_cost * (migs.avg_user_impact / 100.0) *
		(migs.user_seeks + migs.user_scans) > 10
ORDER BY
	migs.avg_total_user_cost * migs.avg_user_impact *
		(migs.user_seeks + migs.user_scans) DESC

It is important to note, that these are index candidates are only candidates and the improvements are based on estimates. The estimated improvement does not take extra disk space requirements and the maintenance of the indexes during updates, inserts and deletes. Furthermore it does not make recommendation about usage of clustered or non-clustered indexes.

This blog post is inspired by Bart Duncan’s Are you using SQL’s missing index DMVs?

Visual Studio 2010 keyboard shortcuts

I am fond of keyboard shortcuts and wish I was a keyboard-shortcut-ninja and didn’t have to rely on the mouse all the time.

Using keyboard shortcuts boosts productivity and ergonomically a better choice, as the risk of getting a tennis elbow/mouse elbow diminish.

Source of keyboard shortcuts for Visual Studio 2010: