3 ms·

To amplify, I do a ton of queue adjustment work with Unicorn at the backlog level. It is so frequent that we set up Unicorn startup to read from an ENV variable

To amplify, I do a ton of queue adjustment work with Unicorn at the backlog level. It is so frequent that we set up Unicorn startup to read from an ENV variable on Heroku that we set as needed. With two Unicorn workers we found that 25 was the best backlog threshold to accept (it refuses additional requests). When we were able to go to 5 Unicorn workers on Heroku we had to start to adjust that.

tibbon 14y ago
You don't happen to have any documentation for how to do that do you? Very curious. Never seen anything about setting up Unicorn like this prior (I'm just using 3 or 4 Unicorns/dyno currently)
- scottshea 14y ago
  We did this in unicorn.rb `:backlog => Integer(ENV['UNICORN_BACKLOG'] || 200)` and then set the UNICORN_BACKLOG variable by the Heroku command line `heroku config:set UNICORN_BACKLOG=25 -a <app_name>`. We have been as high as 1024 and as low as 10. We settled in at 25 for us.
- jwrubel 14y ago
  Here's a gist of our unicorn.rb config (https://gist.github.com/apangeajwrubel/4953849 https://gist.github.com/apangeajwrubel/4953849) Using env variables lets us adjust parameters without a code push (still requires a restart). We saw dramatic reduction in 'long tail' requests when we dropped the backlog to 25. We're experimenting now (thanks to @scottshea) with even lower values. At some point the routing mesh will give up retrying and throw an H21 (https://devcenter.heroku.com/articles/error-codes#h21-backend-connection-refused https://devcenter.heroku.com/articles/error-codes#h21-backen...). One data point that would be useful from heroku is how many retries we get.
- pointful 14y ago
  To expand on this: You have to remove the port declaration from the line for Unicorn in your Procfile, and then add a line like this to your unicorn.rb file to define the listener port along with adjusting the backlog size: listen ENV['PORT'], :backlog => Integer(ENV['UNICORN_BACKLOG'] || 100)

tibbon 14y ago

You don't happen to have any documentation for how to do that do you? Very curious. Never seen anything about setting up Unicorn like this prior (I'm just using 3 or 4 Unicorns/dyno currently)

scottshea 14y ago
We did this in unicorn.rb `:backlog => Integer(ENV['UNICORN_BACKLOG'] || 200)` and then set the UNICORN_BACKLOG variable by the Heroku command line `heroku config:set UNICORN_BACKLOG=25 -a <app_name>`. We have been as high as 1024 and as low as 10. We settled in at 25 for us.
jwrubel 14y ago
Here's a gist of our unicorn.rb config (https://gist.github.com/apangeajwrubel/4953849 https://gist.github.com/apangeajwrubel/4953849) Using env variables lets us adjust parameters without a code push (still requires a restart). We saw dramatic reduction in 'long tail' requests when we dropped the backlog to 25. We're experimenting now (thanks to @scottshea) with even lower values. At some point the routing mesh will give up retrying and throw an H21 (https://devcenter.heroku.com/articles/error-codes#h21-backend-connection-refused https://devcenter.heroku.com/articles/error-codes#h21-backen...). One data point that would be useful from heroku is how many retries we get.
pointful 14y ago
To expand on this: You have to remove the port declaration from the line for Unicorn in your Procfile, and then add a line like this to your unicorn.rb file to define the listener port along with adjusting the backlog size: listen ENV['PORT'], :backlog => Integer(ENV['UNICORN_BACKLOG'] || 100)