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Load Impact & Async Postback Error

Load Impact Performance Testing - Healthy Sites Mean Consistent Testing

I thought I’d post about this as others may have run into this issue and not finding the right information about resolving it. We spent a lot of time googling to no avail.

In anticipation of our largest traffic spike of the year, we ran a load test using Load Impact, a third-party service that bombards your website with virtual users as a means of testing how your servers handle an influx of increasing traffic. For a small fee, of course.

We began a test of 800 VUs over the course of a 1/2 hour and began seeing the following error (ASP.NET):

There was an error
SITE ERROR TYPE: System.InvalidOperationException [500] Error Message: The page is performing an async postback but the ScriptManager.SupportsPartialRendering property is set to false. Ensure that the property is set to true during an async postback. URL:https://www.foo.com/foo USER AGENT:LoadImpactRload/3.2.0 (Load Impact; http://loadimpact.com); REFERRER: Error Stack: at System.Web.UI.ScriptManager.OnPageInitComplete(Object sender, EventArgs e) at System.Web.UI.Page.OnInitComplete(EventArgs e) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

This error came with every request and eventually the server choked. Figuring that we uncovered some major bug, we took to googling, finding fixes from simple to complicated. The thing is, looking back in our error logs, we’ve only seen this error a few times in real life and even then, only coming from some mobile devices. So, we deduced that this error was triggered by Load Impact itself. Sure enough, we changed the user agent, re-ran the tests, and the errors disappeared.

The Load Impact tests default to Load Impact as the user agent. You can change this via the Advanced Settings in the portal or you can add a line at the top of your scripts. Chrome on Windows is, by far, the most popular browser used to visit our website, so we added:

http.set_user_agent_string("Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36")

Easy peasy, no more errors. Hope this fixes your problem.

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TGO 2018: I’m Going to Scotland

Preliminary route of my backpacking trip across Scotland for TGO 2018.

Happy Days!!! I received word that I’m in – I made the cut and I’m eligible for the 2018 TGO (The Great Outdoors) Challenge, a coast to coast Scotland backpacking adventure.

Acceptance email for TGO Challenge 2018, backpacking Scotland coast to coast.
Acceptance email for TGO Challenge 2018, backpacking Scotland coast to coast.

I just sent in my entry fee to make it official and now I have to plan out my route to present to the TGO Challenge vetters. For those who don’t know, the TGO Challenge, in its 39th year, is a self-sustained backpacking trip from the west coast of Scotland to the east coast. Scotland is very unique in that they allow for “wild camping” on most outdoor private and public land and the culture is very accepting of this (unlike here in the States where you’d probably get shot as a trespasser).

So, now I begin the planning. I’m in the infancy stage but my initial thoughts are to:
1. Fly into Glasgow
2. Take a train to Mallaig and sign in
3. Take a ferry to Inverie
4. Backpack several days over to Loch Ness (gotta check out Nessie)
5. Backpack down to Newtonmore, stay in a hostel and have a nice shower
6. Backpack several days over to Aberdeen
7. Take a bus down to Montrose and sign out

Averaging 15 miles a day, this will take me approximately 12+ days to complete. That should allow me an extra day in Aberdeen and an extra day in Montrose if all goes well.

I will post updates as I cement my plans.