Guide: IIS Thread pool optimization

We’ve just released our new IIS Threading guide, which explains how the IIS thread pool works and how it affects your website performance.

It turns out that many people don’t have a clear sense of how the IIS thread pool relates to hangs and slowdowns in their website.

So, we took the opportunity to clear things up, and explain how IIS thread pool exhaustion or thread starvation actually affects IIS site performance.

This includes:

  1. 503 Queue Full errors, or application pool queue buildup
  2. Reduced RPS, especially for high performance websites

We also explain how most traditional hangs and slow loads are NOT caused by IIS threadpool issues, but instead the application-specific thread pools like the CLR thread pool, or the Classic ASP thread pool.

Monitoring IIS thread performance

We also show a simple way to monitor IIS counters to detect IIS pool issues.

If you have LeanSentry installed on the server, you can get a lot deeper into actually diagnosing most thread pool issues down to code (part of our application pool failure diagnostics). We’ll cover this well.

LeanSentry diagnosing IIS thread pool issues causing 503 queue full errors
LeanSentry diagnosing an 503 queue full incident down to code causing CPU overload, which is then causing IIS thread delays.

Optimizing the thread pool

In the guide, we dig into the specific causes of threading issues, that actually happen. This is based on monitoring 30K+ IIS websites with LeanSentry in the last decade.

Surprisingly, there are only a couple causes of thread pool issues that matter.

We’ll cover each one, and how to configure the IIS threadpool to resolve them.

For the juicy details, head over to the thread pool guide.

Guide: Maximum IIS application pool availability

Building on our last week’s Reset, Restart, Recycle IIS guide, this week we are digging deeper into improving IIS application pool availability.

Head over to How to maximize IIS application pool availability to see how you can tweak your IIS websites to:

  1. Start in 100%-warm state, for best cold-start performance (even after a production restart or recycle)
  2. Have zero startup delay (despite the warmup we just mentioned)

Yes, basically you CAN have your cake and eat it too.

Meaning your website is always warm, and can recycle without the users feeling it. This requires getting a lot of pieces right, and guide shows you exactly how to do that.

Best of all, it requires ZERO code.

Configure it all instantly with the ConfigureWarmup tool

We have a tool that will automatically configure the warmup configuration for your website. We’ll be releasing this tool shortly, but if you want it now, be sure to sign up for the Guide newsletter early access. This will allow you to get all our guides, and tools, before they are publicly released online.

Guide: how to restart IIS websites correctly

Our first guide in the IIS Expert guides series is out.

This one is about the right ways to restart IIS websites, and the production impacts of the different ways customers do it.

We also discuss in detail WHEN you should restart IIS or recycle your application pool, and when you shouldn’t … and the better alternatives to restarting.

Improving IIS application pool availability

This post is part 1 of our upcoming series on how to configure IIS for maximum availability. The next guide will touch on how to configure your sites for 100% warm operation, with zero startup delays. We also have a tool called ConfigureWarmup that can do this for you automatically, and can even test your warmup performance. Stay tuned for these coming in the next two weeks.

P.S. Be sure to sign up for the IIS guides newsletter to get early access to all of these.

Expert IIS guides series

It’s hard to believe that LeanSentry is turning 10!

During the last 10 years, we went from a collection of IIS troubleshooting tools that Mike wrote to help fix performance problems for large IIS sites like MySpace, Microsoft mobile, and Vevo to a comprehensive diagnostic service for troubleshooting and optimizing IIS websites.

What’s more, we’ve worked with thousands of companies and IT/developer pros like you to help solve real issues for real applications.

During this time, the number one challenge we’ve heard from our customers is the need for best-practice knowledge, and real-world skills on how to do troubleshooting and optimization. Even with a diagnostic service like LeanSentry, many customers still found it difficult to make the actual changes they needed to resolve their problems.

Get the guides

We personally worked with, and helped thousands of you to do this. Now, we’ll be sharing our techniques and tools we’ve used through the years to empower as many people as possible to run reliable, high performance websites on the Microsoft web platform.

We’ll cover topics like:

  1. How to configure your IIS website for maximum availability,
  2. How to save cloud hosting costs with smart optimizations,
  3. What kind of IIS monitoring helps you fix website issues, and what is a waste of your time,
  4. How to quickly recover from memory leaks, hangs, high CPU issues, queueing, and others,
  5. Best practice application patterns ASP.NET developers can use to build faster, more reliable, more scalable apps,
  6. Tools we use to all these things correctly, and much more

We’ll also look at a bunch of things that DON’T WORK. There are a lot of those … including popular things that take down your website, break your webserver, or cause you to spend 4x more money on your cloud hosting.

To be the first to receive content, be sure to head over to https://www.leansentry.com/guide and sign up for the Guide newsletter.

Sign up for the expert IIS guides newsletter.

See you soon!

Year in Review 2017

You might not know it, but 2017 has been a big year at LeanSentry.

Over the last 5 years, we’ve helped over 10,000 customers take control of production issues in their Microsoft web stack. All the while, we’ve been flying “under the radar” while working out the kinks in our product and our business model. Continue reading Year in Review 2017

Get rid of your unhealthy Azure instances

Have you ever had an Azure instance that just was not performing up to your expectations?

We have. And in the past, they were very hard to get rid of without affecting your entire cloud deployment.

How-To: Remove Azure instances that became slow or unhealthy

In this week’s How-To post, we’ll cover the new API that lets us easily remove an Azure instance that is performing poorly or has become unhealthy. We also share a tool we wrote to automate the removal, so you can remove dead Azure instances quickly whenever you need.

Read more: Azure: Remove unhealthy or slow role instances.

A bit of history

Back when we launched LeanSentry 2 years ago, we had a lot of issues with Azure instances not performing up to our expectations. In particular, the Azure host processes would die whenever the instances experienced high memory utilization from our custom cache layer, and begin to constantly recycle the role/reboot the VM. This caused service outages during times of peak usage.

Back then, the only way to take an instance out of rotation was to do VIP swap, or to scale down the service to a point where the offending instance would be removed (and so would all other instances with higher instance ids). Because we maintained a lot of in-memory and on-disk state on the instance, both of those options would be a huge no-no. So, we lobbied Microsoft to create an option to remove a specific instance, instead of trashing half of your service.

The Azure team came through and finally released an API to do this. This has been a godsend, allowing us to intelligently manage how we scale up and down so we can keep the instances with the highest efficiency / warmest cache.

For more on how to when to do this, and a tool to quickly delete instances, check out the How-To post here.

LeanSentry How-To: IIS & ASP.NET recommendations from our team

In the last 2 years, we’ve helped thousands of big and small companies to improve their IIS servers & ASP.NET applications.

Today, we are announcing LeanSentry How-To: a series of best-practice guides to help you solve common performance problems & improve your site health.

We’ll cover topics like:

1. Azure best practices
2. IIS & ASP.NET performance
3. Improving application & server stability
4. Advanced tools & techniques for troubleshooting production problems

To get these, sign up for our How-To series at LeanSentry How-To.

If you have specific areas or questions you would like to see covered, email us or post them here anytime.

Fix IIS & ASP.NET hangs faster with Hang diagnostics

Automatic hang diagnostics for IIS & ASP.NET apps has been one of LeanSentry’s most popular features.

Now, Hang diagnostics are getting even better, with more expert insight into hangs, better root cause detection, and more code-level data for your developers.

Automatically diagnose ASP.NET hangs

LeanSentry’s Hang diagnostics feature helps you resolve your website’s slowdowns, better than you can with generic monitoring tools. It does this by detecting and by automatically diagnosing dozens of common IIS, ASP.NET, and Classic ASP performance problems whenever your site experiences them.

No intrusive profilers, DebugDiag, or other tools needed. Like most of LeanSentry, hang diagnostics have virtually zero overhead during normal operation, and only a small overhead (5-10 seconds of analysis) when a problem is confirmed. This means you can add LeanSentry’s deep diagnostic insight to your existing monitoring without any conflicts or performance drops.

What’s new?

A lot! We’ve improved the diagnostic algorithms to detect more problems. Then there is the brand new diagnostic report interface that gives you better guidance, and more information on what caused the hangs.

See the actual IIS & ASP.NET operation

See the real request flow during ASP.NET hangs
See the actual request flow, and the key IIS & ASP.NET performance issues during the hang.

Expert guidance

Full ASP.NET hang analysis
LeanSentry analyzes the specific causes of the hang in your app, and gives you best practice guidance on how to address it.

Identify the function, slow SQL, REST call causing blocking

Diagnose ASP.NET hangs down to code, SQL query, and more
LeanSentry automatically determines the application code causing request blocking or thread pool exhaustion, and shows your the line of code, SQL query, REST url, or file being accessed.

Try it out

If you are still troubleshooting hangs the hard way, or trying to use the generic transaction monitoring tools, you are missing out. To learn more, check out LeanSentry’s hang diagnostics, and do a trial to see it for yourself.