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Lag with live pages with >100 participants

#1 by Rok


I am inquiring about the limits of live pages concerning a larger number of participants.

We are hosting a game on Heroku with about 120 participants at a time, ideally increasing to 200. The game features two simple live functions and a chat feature.

In the first part of the game, participants engage in an effort game for 3 minutes. Every few seconds, they submit an answer, triggering two live function calls (browser->server->browser x2).

In the next part of the game, which some participants may reach while others are still in the first part, we use a built-in chat feature for pairs of participants and a live function call to update another participant's slider position upon slider change. (It only triggers one live function call on slider change and does not trigger while dragging.)

Bot testing with 150 bots did not reveal any specific non-live function lag sources; the bots played the game without issues.

However, participants are experiencing extreme server lag, resulting in them getting stuck and timing out of the experiment after waiting for several minutes.

Are there any known issues with live games, or suggested limits on the number of live calls per second or participants playing a live game? Are there recommended ways to set up Heroku to better support live games, such as adding specific additional dynos? A few years ago, when live functions were new to oTree, I experienced similar issues with a different game, and the only solution that worked at the time was removing a significant portion of my live code. This time, I can't do this.

Thank you for your assistance,

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