High-CPU / High memory on fresh discourse install

I have been attempting to install the official version of discourse on my docker host. I have followed the instructions for setting up a standalone server, with the modification to run behind a proxy in order to share the ports with other sites I have (non-discourse). However, after installing and building, the resulting site is taking over the resources of the box, and nearly freezes all other processes, rendering the box inoperable, until I manage to forcefully kill the container.

This is the app.yml I am currently using:

## this is the all-in-one, standalone Discourse Docker container template
## After making changes to this file, you MUST rebuild
## /var/discourse/launcher rebuild app
## visit http://www.yamllint.com/ to validate this file as needed

  - "templates/postgres.template.yml"
  - "templates/redis.template.yml"
  - "templates/web.template.yml"
  - "templates/web.ratelimited.template.yml"
## Uncomment these two lines if you wish to add Lets Encrypt (https)
  #- "templates/web.ssl.template.yml"
  #- "templates/web.letsencrypt.ssl.template.yml"

## which TCP/IP ports should this container expose?
## If you want Discourse to share a port with another webserver like Apache or nginx,
## see https://meta.discourse.org/t/17247 for details
  - "80"

  db_default_text_search_config: "pg_catalog.english"

  ## Set db_shared_buffers to a max of 25% of the total memory.
  ## will be set automatically by bootstrap based on detected RAM, or you can override
  db_shared_buffers: "1024MB"

  ## can improve sorting performance, but adds memory usage per-connection
  #db_work_mem: "40MB"

  ## Which Git revision should this container use? (default: tests-passed)
  #version: tests-passed

  LANG: en_US.UTF-8

  ## How many concurrent web requests are supported? Depends on memory and CPU cores.
  ## will be set automatically by bootstrap based on detected CPUs, or you can override

  ## TODO: The domain name this Discourse instance will respond to
  ## Required. Discourse will not work with a bare IP number.
  DISCOURSE_HOSTNAME: discourse.belmankraul.com
  VIRTUAL_HOST: 'discourse.belmankraul.com'

  ## Uncomment if you want the container to be started with the same
  ## hostname (-h option) as specified above (default "$hostname-$config")

  ## TODO: List of comma delimited emails that will be made admin and developer
  ## on initial signup example 'user1@example.com,user2@example.com'
  DISCOURSE_DEVELOPER_EMAILS: '[my developer email]'

  ## TODO: The SMTP mail server used to validate new accounts and send notifications
  # SMTP ADDRESS, username, and password are required
  # WARNING the char '#' in SMTP password can cause problems!
  DISCOURSE_SMTP_ADDRESS: [my smtp server]
  DISCOURSE_SMTP_USER_NAME: [my smtp username]
  #DISCOURSE_SMTP_ENABLE_START_TLS: true           # (optional, default true)

  ## If you added the Lets Encrypt template, uncomment below to get a free SSL certificate

  ## The CDN address for this Discourse instance (configured to pull)
  ## see https://meta.discourse.org/t/14857 for details
  #DISCOURSE_CDN_URL: //discourse-cdn.example.com

## The Docker container is stateless; all data is stored in /shared
  - volume:
      host: /root/docker-persist/discourse/shared/standalone
      guest: /shared
  - volume:
      host: /root/docker-persist/discourse/shared/standalone/log/var-log
      guest: /var/log

## Plugins go here
## see https://meta.discourse.org/t/19157 for details
    - exec:
        cd: $home/plugins
          - git clone https://github.com/discourse/docker_manager.git

## Any custom commands to run after building
  - exec: echo "Beginning of custom commands"
  ## If you want to set the 'From' email address for your first registration, uncomment and change:
  ## After getting the first signup email, re-comment the line. It only needs to run once.
  #- exec: rails r "SiteSetting.notification_email='info@unconfigured.discourse.org'"
  - exec: echo "End of custom commands"

docker_args: "--network reverse-proxy"

It was copied straight off of standalone.yml in samples, with the modifications for it to work under a reverse proxy (using jwilder/nginx-proxy). In order to achieve this, I have a separate network, called reverse-proxy. All of that works perfectly after the site manages to build (the 6-8mins). The setup wizard comes up, I am able to enter all of my data. But when I finish it, the site just locks up, processor and memory usage spike, and the whole host box slows to a crawl. I have to then kill the container, in order to bring back stability to the box. My initial setup was a 4VCPU, 4GB of RAM, 60GB. I have now increased RAM to 8GB, to no avail. Any idea what is going on?

I must confess I am one of the ones who would very much rather prefer a standard docker / docker-compose implementation. I have seen the arguments for and against. I am currently having to resort to the bitnami implementation of discourse, which supports docker-compose nicely, but is behind in updates from master, until I can overcome the official implementation problem.

Thanks in advance for the help.

I have a few questions!

  1. Why do you need a reverse proxy network when there are more efficient ways of doing it?
  2. I’ve never heard of the variable VIRTUAL_HOST in regards to discourse

With that, I’d say that there is something wrong with your configuration, Please try installing discourse on a separate machine if possible . (of course, on the same provider) to check if it is discourse or something else on your existing server that is causing the resource spike.

You said this server hosts other sites. Figure out your baseline load on CPU and memory. Subtract used from available to gauge sane settings on your unicorns, db_worker & shared_buffers.

You might want to first try dropping your unicorns down to 3 and the shared buffers to something like 384MB. If that does it you might just have a fairly well loaded server (or noisy neighbors).



  1. I am using a reverse proxy network because it is recommended as optimal for using the proxy container that I run all of my solutions with.

  2. As mentioned in my original post, I am using jwilder/reverse proxy, which uses the VIRTUAL_HOST env variable to proxy the web traffic based on host name. This has been extensively talked about here at meta, and it works quite well. I have no issues with that part. More about that here:

One of the biggest questions I have about having to run Discourse on a separate machine is, why docker, then? The other thing… The minimal resource requirement is 1GB. I can’t for the life of me understand why 4GB or even 8GB would not be enough, for operation in a shared container environment. This is an on-premises ESXi vm setup, sure, I could create a separate virtual machine for this… But the question remains…why docker, then? I am assuming that by “my configuration” you mean my docker version, host OS etc (since I posted my app.yml config already). It is as follows:

Ubuntu 18.04.1 LTS x64

Docker-ce 18.06.1-ce

You just set the unicorn workers and shared_buffers to high for a shared machine.

Try setting to the values @boredomdenied suggested and rebuilding.


Rafael, you and @boredomdenied were correct. After setting my worker and shared_buffers values to what was recommended, everything is working perfectly. Thank you all for your help. I am marking @boredom’s reply as the solution.