Valuable Extended Events Sessions

Derik Hammer has a few useful extended events sessions that he’s sharing with us:

Extended Events are the all-around smart choice. They take a little bit of time to get used to, however. With thousands of new events and data points, it can be difficult to create an event session in a pinch. That is why it is important to have event sessions pre-scripted or pre-implemented on your SQL Server instances. A little bit of up-front work can save you a lot of time when you need information on the spot. Having them pre-scripted also prevents you from jumping back to Profiler, which has a much heavier footprint on your server.

When I create Extended Event sessions, I tend to use the SQL Server Management Studio wizard to find the events and actions (additional fields) that I want. Then, I will script it out and save it for later.

Below are five Extended Events sessions that I have found particularly useful and recommend you add to your toolbox.

Click through for all of those scripts, as well as queries to shred the resulting XML.

XESmartTarget: Event Handling With SQL Server

Gianluca Sartori introduces a new tool to help with event handling in SQL Server:

I am proud to introduce XESmartTarget: the easiest way to interact with extended events sessions without writing a single line of code.

XESmartTarget uses the Extended Events streaming API to connect to a session and execute some actions in response to each event. The actions you perform can be configured in a simple .json file, which controls the Response types and all their properties.

For instance, if you have a session to capture deadlocks, you may want to be notified whenever such an event is captured. All you need to do is configure XESmartTarget to send an email using the EmailResponse class. You can do that by creating a simple .json file with all the parameters needed

This looks quite interesting.

Extended Events Profiler

Marek Masko shows off the new Extended Events Profiler In SQL Server Management Studio 17.3:

XE Profiler looks promising and can be really a great feature. We can use it with no issues on any version of SQL Server which supports extended events – not only with newest SQL Server 2017. I tested it with SQL Server 2014 and it was working well. Currently, lack of configuration of new templates, and logic based on hard-coded names is the biggest concern and discomfort for the user. However Microsoft didn’t officially release yet this version of SQL Server Management Studio, so it’s hard to say what will be the final feature functionality.

I’m hoping that when the final version appears, it will be good enough to get people finally to kick the Profiler habit.

New Extended Events In SQL Server 2017

Erik Darling unwraps some of his Christmas presents a bit early:

There are, as of RC2 being released, 194(!) new Events to Extend your mind with. Not all of them are interesting to me, and I haven’t had time to pry into all of the ones that are interesting just yet.

This is a rundown of the new Events with names or descriptions that I found interesting, and will try to spend some time with.

I can’t promise anything

After all, getting some of these to fire is tougher than using a Debugger.

There are some interesting events here.

Data-Driven Fill Factors

Tracy Boggiano has an Extended Event and a procedure to track page splits and then modify index-level fill factors accordingly:

So what is the solution?  Well it really depends.  But the solution I wrote walks you through

  • Setting the default fill factor

  • Tracking page splits

  • Lowering the fill factor

Read on to learn more.

How Long Was That Event?

Taiob Ali shows that some extended event times are in milliseconds, some are in microseconds, and some are in unknownaseconds:

There was a question in dba.stackexchange.com titled “module_end extended events duration in microseconds?” that I answered and it was Microsecond in that instance.
Later on I questioned myself if the duration is always in Microseconds for extended events. I found, it is a mix of Millisecond, Microsecond and some are unknown meaning famous NULL. I wrote below tsql code to determine which is what.

Click through for the script that Taiob used to determine the answer.

Availability Group Extended Events

Tracy Boggiano shows how to enhance the built-in Extended Events session for Availability Groups:

Now that the extended events session is setup we can use some queries to query information about our AGs and error messages happening on our servers.  First to query when the server failover and becomes your primary server query the event availability_replica_state_change.  The first 10 lines just read in the files for the extended event session so you don’t have to identify the exact filenames.  Then we parse the xml event for get the timestamp, previous state, current state, repliace name, and group name for the event FROM the filenames we collected before.  In the WHERE clause were are looking for when the state has changed to PRIMARY_NORMAL indicating a failover to the server.

Read on for scripts showing what she extends and also how to query this data.

System Health XE

Kenneth Fisher describes what is in the system_health Extended Events session:

Per BOL you get the following information:

  • Errors with a severity of >= 20.

  • Memory related errors (Errors 17803, 701, 802, 8645, 8651, 8657 and 8902).

  • Non-yielding scheduler problems (Error 17883).

  • Deadlocks.

  • Sessions that have waited on locks for > 30 seconds.

  • Sessions waiting for a long time on preemptive waits (waits on external API calls).

Read on to learn more of the things this session contains as well as a couple ways you can access the data.

Finding Failed Queries

Andrew Pruski shows how to use extended events to find queries with errors:

What this is going to do is create an extended event that will automatically startup when the SQL instance starts and capture all errors recorded that have a severity level greater than 10.

Full documentation on severity levels can be found here but levels 1 through 10 are really just information and you don’t need to worry about them.

I’ve also added in some extra information in the ACTION section (for bits and bobs that aren’t automatically included) and have set the maximum number of files that can be generated to 10, each with a max size of 5MB.

Check it out.  At one point, I had created a small WPF application to show me errors that extended events caught.  It completely freaked out a developer when I IM’d him and told him how to fix the query he’d just run from the privacy of his cube, with me nowhere to be seen.

Extended Event Handler Application

Dave Mason whipped up an application to track when a particular extended event fires:

Event Responses: when an event is handled, specify how you want to respond to it. In the “Event Responses” section, there are two options: play a system sound or send email (you must choose at least one option). Pick the system sound desired and/or enter an email address.

Dave has made the source code available as well so you can extend the functionality.

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November 2017
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