On Wednesday, April 16, 2014 6:37:53 PM UTC-7, Zhannan Ge wrote:
>
> The cause of this issue is our server changes the shard of all models in
> before filter for each request based on if the coming request method is
> "GET" or non-"GET"(POST, PATCH, PUT)
>
> If it's a "GET" request, we do
> ALL_MODELS.each { |model| model.dataset = model.dataset.server(:slave) }
>
> otherwise, we do
> ALL_MODELS.each { |model| model.dataset = model.dataset.server(:master) }
>
> The idea behind this is that, we do not want to choose whether to use
> master or slave based on if the query is a "SELECT", instead we want to
> choose slave for "GET" requests, and master for non-"GET" requests.
>
> The problem can be reproduced by the following steps:
> 1. start the server
> 2. make as many "POST" requests as you want, and the the rollback works
> fine
> 3. make a "GET" request, which would change all the models to point to
> :slave
> 4. make a "POST" request, which would change all the models back to
> :master, and the rollback starts to fail from now on just as Gabe
> N describes.
>
> If you could let us know why is this causing the problem, if we are doing
> something wrong and if you have any alternative suggestions to approach
> this.
>
Changing all models' datasets per request is not how you want to handle
this. Use the server_block extension in conjunction with a rack middleware
to change the default server per request.
I'm not sure what exactly is going wrong with the way you currently have
things setup. I would need a self-contained reproducible example to debug
something like that. However, it's pointless to expend that effort if the
server_block approach will solve the problem.
Thanks,
Jeremy
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