AnyCable

This guide shows you how to replace Action Cable with AnyCable. Both provide similar functionality, but have different scaling characteristics. While AnyCable has the potential to reduce RAM requirements on large deployments, the need to run multiple processes makes it impossible to run AnyCable alongside even a tiny Rails application on a 256MB machine. A minimum of 512MB is required.

The configuration below also runs nginx as a reverse proxy to avoid any firewall issues.

Prepare Your Application

If you haven't already dones so, perform the steps described in the Provisioning Redis section of the Getting Started guide. Also be sure that the pg gem is listed in your Gemfile.

Now add the anycable-rails gem:

bundle add anycable-rails

Edit config/cable.yml thus:

 production:
-  adapter: redis
-  url: <%= ENV.fetch("REDIS_URL") { "redis://localhost:6379/1" } %>
-  channel_prefix: namelist_production
+  adapter: any_cable

Update Your Image

Modify Dockerfile to install foreman, anycable-go and nginx:

 FROM base

+RUN gem install foreman
+RUN curl -L https://go.dev/dl/go1.19.linux-amd64.tar.gz | tar xz -C /opt
+RUN GOBIN=/usr/local/bin /opt/go/bin/go install github.com/anycable/anycable-go/cmd/anycable-go@latest
+
-ARG PROD_PACKAGES="postgresql-client file vim curl gzip libsqlite3-0"
+ARG PROD_PACKAGES="postgresql-client file vim curl gzip libsqlite3-0 nginx"
 ENV PROD_PACKAGES=${PROD_PACKAGES}

 RUN --mount=type=cache,id=prod-apt-cache,sharing=locked,target=/var/cache/apt \
     --mount=type=cache,id=prod-apt-lib,sharing=locked,target=/var/lib/apt \
     apt-get update -qq && \
     apt-get install --no-install-recommends -y \
     ${PROD_PACKAGES} \
     && rm -rf /var/lib/apt/lists /var/cache/apt/archives
+
+ADD config/nginx.conf /etc/nginx/sites-available/default

 COPY --from=gems /app /app
 COPY --from=node_modules /app/node_modules /app/node_modules

Edit fly.toml to run foreman::

 [env]
   PORT = "8080"
-  SERVER_COMMAND = "bin/rails fly:server"
+  SERVER_COMMAND = "foreman start -f Procfile.fly"

Add Procfile.fly to start the four processes required:

nginx: nginx -g 'daemon off;'
server: bin/rails server -p 8081
anycable: bundle exec anycable
ws: anycable-go --port=8082

Add config/nginx.conf to reverse proxy cable traffic to anycable-go and send the remainder to your Rails application::

server {
        listen 8080 default_server;
        listen [::]:8080 default_server;

        location /cable {
                proxy_pass http://localhost:8082/cable;
                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection "Upgrade";
                proxy_set_header Host $host;
        }

        location / {
                proxy_pass http://localhost:8081/;
                proxy_set_header origin 'https://localhost:8081';
        }
}

Deployment

If you haven't already done so, scale your machine:

fly scale vm shared-cpu-1x --memory 512

Now you are ready to deploy:

fly deploy