World of Warcraft has been running for 22 years, and even now, Blizzard sometimes struggles to meet player demand. Yesterday, World of Warcraft: Ever opened its test phase, only to have its servers crash immediately due to a surge of players. With decades of experience launching MMO content, why did this happen? The developers said they were completely caught off guard by how popular the Ever test would be.
Senior Game Designer Josh Greenfield posted on Twitter, "Wow, I was so excited last night I couldn't sleep. The test results... were insane. These are the most outrageous numbers I've seen in my 17 years at Blizzard and nearly 8 years working on the Classic project. What we've done this time is truly extraordinary."
This might sound like an exaggeration, but Senior Game Producer Tom Ellis released a more detailed technical analysis explaining the causes of the initial glitches during the Ever launch test. Ellis clarified on Twitter, "This is not a production-level server cluster by any means. The WoW test servers usually don't experience significant traffic fluctuations, so the environment wasn't configured for high capacity."
Ellis stated that because "our small test environment only had one realm server enabled," a massive influx of players suddenly converged on this single access point, causing the server's processing logic to fail. This is why players experienced frequent disconnections after enduring long login queues.
It took the developers "about half an hour" to pinpoint this bottleneck, as both the game itself and the Battle.net service showed extremely low load. Ellis explained, "We all knew that this system needed more logging and notification alerts when triggered, but this was the first time anyone had encountered a trigger without obvious CPU anomalies. After twenty years, you still run into new problems."
Ellis also mentioned latency issues players experienced during server-responsive actions like looting items and accepting quests. "Our brave Oracle database engineers had to perform manual analyses on all data tables and set up some automated tasks for regular maintenance," but due to the excessively high frequency of server access, the standard processing rate couldn't keep up. Once the developers resolved this issue, database performance "immediately returned to normal."
Server restarts were also performed. Ellis explained, "A few hours after launch, we noticed that the CPU usage of the world server pool running the game simulation spiked, and memory was nearly exhausted." Empty maps were not being closed correctly, and these processes were slowly—or "actually not that slowly"—consuming server CPU and memory. The developers found a fix, but it required a server restart to take effect. Blizzard also used this opportunity to add more world servers and expand realm services to further improve stability.
Back in 2019, media outlets interviewed several developers about why major online games always crash at launch, suggesting these old issues inevitably recur. One developer once said it was "impossible" to completely solve these launch problems, and the situation with World of Warcraft: Ever proves that new issues always arise with each launch. That said, at least fixes are much faster now. I still remember how players struggled for weeks to play properly after the release of Diablo III...