¿Contenedor de Discourse con UnixSocket para Redis?

[ryanerwin]

Curious if anyone is using unixsocket /var/discourse/shared/... for Redis in their Standalone container? Seems redis-rb also supports domain sockets with:

redis = Redis.new(path: "/var/discourse/shared/standalone/redis.sock")

Apparently connecting via the Unix Domain Socket is about 20% faster than using TCP sockets, according to this article on medium…

Also, using Unix Domain Sockets would make it easier to run multiple standalone containers without separating your web and data containers… Otherwise I think you’ll end up with conflicts with Redis listening on 127.0.0.1…

I’m trying to setup two completely standalone containers on one host right now, and since they’re both for very small sites, I would prefer the flexibility of keeping them in standalone containers… Unfortunately Redis listening on 127.0.0.1 (and presumably Postgres too) will conflict…

[neounix (Dark Matter)]

@ryanerwin

Also, using Unix Domain Sockets would make it easier to run multiple standalone containers without separating your web and data containers… Otherwise I think you’ll end up with conflicts with Redis listening on 127.0.0.1…

Hi @ryanerwin

Seems you are not fully understanding containers and docker a bit; so let me help you out.

Redis runs by default in the standalone container on port 6379:

cd /var/discourse
./launcher enter app
apt install net-tools
netstat -an | grep :6379 |wc -l 

74

Now lets exit the container and check netstat for Redis:

exit
root@localhost:/var/discourse# netstat -an | grep :6379 |wc -l 
0

So, you can see that Redis is listening on localhost inside the container; and localhost inside the container was (is) not exposed outside the container.

Hence, if you have many standalone discourse containers running, there would not be any Redis conflicts between containers because Redis has not been exposed outside each container.

That’s why it’s called a “container”…

Every socket inside the container must be explicitly exposed to be available outside the container.

Hope this helps in some small way.

---

Note that unix domain sockets are very cool… I only addressed your comment about perceived Redis conflicts between standalone containers and did not address the unix domain socket topic.

[ryanerwin]

@neounix

Hence, if you have many standalone discourse containers running, there would not be any Redis conflicts between containers because Redis has not been exposed outside each container.

That’s how I thought it would work with discourse running inside of Docker too, however when I actually ran it, during the bootstrapping process I saw:

INFO -- : > cd /var/www/discourse && git reset --hard
# oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
# Redis version=5.0.5, bits=64, commit=00000000, modified=0, pid=195, just started
# Configuration loaded
# Could not create server TCP listening socket *:6379: bind: Address already in use
Checking out files: 100% (27893/27893), done.

And I had found this thread about “install fails because of other redis container”, however the problem actually was low disk space… Reorganized some things and it does work just fine with multiple standalone containers.

[neounix (Dark Matter)]

@ryanerwin

Reorganized some things and it does work just fine with multiple standalone containers.

Dear @ryanerwin,

It’s great to read that you have found the underlying issue and now understand that Redis runs “in the container” and is not exposed (from a socket I/O perspective) outside the container (as set up OOTB).

Regarding using unix domain sockets and Redis, I think this is a great idea and have not set this up (yet), and nor have I read any write-up on how to set this up for Discourse, and so I would encourage you to continue to explore this option.

If I have time, I will research this further and try to set up Redis to use a unix domain docket in Discourse on a staging server. In the meantime, if you can work this out and post your results, that would be much appreciated. I’m sure many others are also interested in this interesting Redis topic.

Thanks.

[neounix (Dark Matter)]

@ryanerwin

Curious if anyone is using unixsocket /var/discourse/shared/... for Redis in their Standalone container? Seems redis-rb also supports domain sockets with:

Hi @ryanerwin,

I hope you will be happy to hear that I have Discourse running with Redis using a unix socket in a standalone container, just like you asked about.

Check out the bottom of this screen shot from sidekiq:

In addition, here are some more screenshots from building the app:

My next steps are to:

1. Move the unix socket to the shared volume so it can be accessed outside the container.
2. Retesting with minimal ENV vars to get the “bare bones” changes to get this up and running.

Basically, I have created this new template:

-rw-r–r-- 1 root root 2028 Jun 6 08:13 redis.socketed.template.yml

and made minor changes to old friend app.yml

Since I only started on this today, I plan to test a bit more before publishing the details.

Hope this will be helpful.

---

Update

---

Works as expected outside the container when the unix socket is on a shared volume:

[neounix (Dark Matter)]

PR for this:

https://github.com/discourse/discourse_docker/pull/469

Note:

To implement:

• Change the redis template in the container yml file
• Add one additional line to the same container yml file

 ## Set the REDIS_URL and use the redis.socketed.template.yml to use 
 ## a unix domain socket for Redis
 REDIS_URL: unix:///shared/tmp/redis.sock

Implementation Notes:

1. If concerned about security of the Redis DB on the host, no need to expose this unix socket in the shared volume.

2. If you wish to set the permissions of the unix socket to 770 (instead of 777) , change the group of the unix socket to www-data.

[MichaIng]

¿Alguien más ha notado que REDIS_URL ya no tiene ningún efecto? Durante la (re)compilación y también al iniciar el contenedor, a pesar de que REDIS_URL está configurado para conectarse a través de un socket UNIX, intenta conectarse a través de redis://localhost:6379.

Por un lado, tiene sentido, ya que Discourse tiene configuraciones para host y puerto y solo las aplica: discourse/app/models/global_setting.rb at main · discourse/discourse · GitHub
Habría un parámetro path para definir una ruta de socket UNIX, que anularía el host y el puerto. Y habría un parámetro url, para definir una URL completa como unix:///shared/redis_data/redis.sock.

La gema de Redis documenta que la variable de entorno REDIS_URL anularía cualquier otra configuración, y hasta cierta versión de la gema Discourse/Redis esto funcionaba: redis-rb/lib/redis.rb at master · redis/redis-rb · GitHub

El uso del socket UNIX se rompió cuando Discourse pasó a la versión 5 de las gemas de Redis: DEV: Upgrade the Redis gem to v5.4 · discourse/discourse@2ed31fe · GitHub
Así que supongo que REDIS_URL se rompió en la gema de Redis (ya no anula otras opciones), y no por Discourse (donde el código relacionado no cambió).

Probablemente este commit lo rompió: Use redis-client as transport · redis/redis-rb@08a2100 · GitHub
¿Lo informaría en el repositorio de la gema de Redis, o alguien sabe que es un problema con la forma en que Discourse lo implementa?

La variable de entorno, por cierto, se pasa correctamente. La dejé en su lugar y solo configuré Redis para que no escuchara en el socket UNIX, y mientras unicorn se inicia sin problemas, sidekiq falla, echando de menos el socket UNIX en su lugar :

Error in demon processes heartbeat check: No such file or directory - connect(2) for /shared/redis_data/redis.sock
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client/ruby_connection.rb:116:in `initialize'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client/ruby_connection.rb:116:in `new'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client/ruby_connection.rb:116:in `connect'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client/ruby_connection.rb:51:in `initialize'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client.rb:759:in `new'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client.rb:759:in `block in connect'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client/middlewares.rb:12:in `connect'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client.rb:758:in `connect'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client.rb:745:in `raw_connection'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client.rb:705:in `ensure_connected'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/redis-client-0.24.0/lib/redis_client.rb:285:in `call'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/redis_client_adapter.rb:36:in `block (2 levels) in <module:CompatMethods>'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/api.rb:912:in `block in cleanup'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/config.rb:175:in `block in redis'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/connection_pool-2.5.3/lib/connection_pool.rb:110:in `block (2 levels) in with'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/connection_pool-2.5.3/lib/connection_pool.rb:109:in `handle_interrupt'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/connection_pool-2.5.3/lib/connection_pool.rb:109:in `block in with'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/connection_pool-2.5.3/lib/connection_pool.rb:106:in `handle_interrupt'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/connection_pool-2.5.3/lib/connection_pool.rb:106:in `with'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/config.rb:172:in `redis'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq.rb:74:in `redis'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/api.rb:912:in `cleanup'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/api.rb:903:in `initialize'
/var/www/discourse/lib/demon/sidekiq.rb:25:in `new'
/var/www/discourse/lib/demon/sidekiq.rb:25:in `heartbeat_check'
config/unicorn.conf.rb:131:in `block (2 levels) in reload'

Encaja en el cuadro que REDIS_URL todavía funciona, pero solo si la configuración de conexión no está definida de otra manera. Mirando el rastro del error, global_setting.rb no aplica el host y el puerto para sidekiq, como lo hace para unicorn.