Participant Numbers and postgress connections

[Jonas]

On heroku, in addition to the database size and RAM the maximum nuber of connections also varies between different postgress plans. I am wondering if there is a relation between the number of otree participants and the number of postgress connections used. I vaguely remember that I had database issues with sessions that had more participants than the maximum amount of connections my heroku plan offered a couple of years ago but I tried to reproduce this with the latest version of oTree 5 and it seemed to work with more participants than the connection limmit. 

[Chris @ oTree]

the number of database connections is not related to the number of participants. Rather, it is related to the number of server processes. In the simplest setup, each process has 1 database connection. Now that oTree runs in a single main process, it uses fewer connections than before, when there were 3 processes that used connection pooling which further complicates things. 

In reality, there may be a few more connections active. For example there is actually a second process that runs a task queue. I haven’t confirmed this but I would expect that the new version should only use like 5 or fewer connections even when there are many participants.

Sent from my phone

On Jun 9, 2021, at 8:01 AM, Jonas <jonasf...@gmail.com> wrote:

On heroku, in addition to the database size and RAM the maximum nuber of connections also varies between different postgress plans. I am wondering if there is a relation between the number of otree participants and the number of postgress connections used. I vaguely remember that I had database issues with sessions that had more participants than the maximum amount of connections my heroku plan offered a couple of years ago but I tried to reproduce this with the latest version of oTree 5 and it seemed to work with more participants than the connection limmit. 

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