Hi, I’m just getting started with Docker, so apologies in advance if this seems silly.
I used to self-host multiple services (RSS reader, invoicing software, personal wiki) directly on a VPS using nginx and mariadb. I messed it up recently and am starting again, but this time I took the docker route.
So I’ve set up the invoicing software (InvoiceNinja), and everything is working as I want.
Now that I want to add the other services (ttrss and dokuwiki), should I set up new containers? It feels wasteful.
Instead, if I add additional configs to the existing servers that the InvoiceNinja docker-compose generated (nginx and mysql), I’m worried that an update to Invoiceninja would have a chance of messing up the other setups as well.
It shouldn’t, from my understanding of how docker containers work, but I’m not 100% sure. What would be the best way to proceed?
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I would suggest having an nginx as a reverse proxy (I prefer avoiding a container as it’s easier to manage) and the have your services in whatever medium you prefer.
Yes, that’s exactly what I’m doing now, I was only unsure about how to map the remaining services - in the same docker containers, or in new ones.
Separate. That’s the whole point of containerisation! Otherwise you’re just doing a regular deploy with extra steps
Thank you. Yes makes sense. I guess it’s fairly obvious in hindsight.
Use new containers, that’s what they’re for.
That would be ideal, per my understanding of the architecture.
So will docker then minimize the system footprint for me? If I run two mysql containers, it won’t necessarily take twice the resources of a single mysql container? I’m seeing that the existing mysql process in
topis using 15% of my VPS’s RAM, I don’t want to spin up another one if it’s going to scale linearly.AFAIK it won’t and should you still get a bottleneck you can limit the maximum resources a service may use.
it won’t necessarily take twice the resources of a single mysql container
It will as far as runtime resources
You can (and should) just use the one MySQL container for all your applications. Set up a different database/schema for each container
I’m getting conflicting replies, so I’ll try running separate containers (which was the point of going the docker way anyway - to avoid version dependency problems).
If it doesn’t scale well I may just switch back to non-container hosting.
If I run two mysql containers, it won’t necessarily take twice the resources of a single mysql containers
It’s complicated, but essentially, no.
Docker images, are built in layers. Each layer is a step in the build process. Layers that are identical, are shared between containers to the point of it taking up the ram of only running the layer once.
Although, it should be noted that docker doesn’t load the whole container into memory, like a normal linux os. Unused stuff will just sit on your disk, just like normal. So rather, binaries or libraries loaded twice via two docker containers will only use up the ram of one instance. This is similar to how shared libraries reduce ram usage.
Docker only has these features, deduplication, if you are using overlayfs or aufs, but I think overlayfs is the default.
Should you run more than one database container? Well I dunno how mysql scales. If there is performance benefit from having only one mysqld instance, then it’s probably worth it. Like, if mysql uses up that much ram regardless of what databases you have loaded in a way that can’t be deduplicated, then you’d definitely see a benefit from a single container.
What if your services need different database versions, or even software? Then different database containers is probably better.
This how I do it, not saying it’s the best way, but serves me well :).
For each type of application, 1 docker-compose.yaml. This will have all linked containers in 1 file but all your different applications are seperate !
Every application in it’s respective folder.
- home/user/docker/app1/docker-compose.yml
- home/user/docker/app2/docker-compose.yml
- home/user/docker/app3/docker-compose.yml
Everything is behind an application proxy (traefik in my case) and served with self-signed certificate.
I access all my apps through their domain name on my LAN with wireguard.
Yes this is what I want to do. My question is how docker manages shared processes between these apps (for example, if app1 uses mysql and app2 also uses mysql).
Does it take up the RAM of 2 mysql processes? It seems wasteful if that’s the case, especially since I’m on a low-RAM VPS. I’m getting conflicting answers, so it looks like I’ll have to try it out and see.
Nah, that’s not how it works ! I have over 10 applications and half of them have databases, and that’s the prime objective of containers ! Less resource intensive and easier to deploy on low end machines. If I had to deploy 10 VMs for my 10 applications, my computer would not be able to handle it !
I have no idea how it works underneath, that’s a more technical question on how container engines work. But if you searx it or ask chatGPT (if you use this kind of tool) i’m sure you will find out how it works :).
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I’ve seen in this thread:
Fewer Letters More Letters HTTP Hypertext Transfer Protocol, the Web VPS Virtual Private Server (opposed to shared hosting) nginx Popular HTTP server
2 acronyms in this thread; the most compressed thread commented on today has 7 acronyms.
[Thread #436 for this sub, first seen 18th Jan 2024, 10:55] [FAQ] [Full list] [Contact] [Source code]
So from what i get reading your question, i would recommend reading more about container, compose files and how they work.
To your question, i assume when you are talking about adding to container you are actually referring to compose files (often called ‘stacks’)? Containers are basically almost no computational overhead.
I keep my services in extra compose files. Every service that needs a db gets a extra one. This helps to keep things simple and modular.
I need to upgrade a db from a service? -> i do just that and can leave everything else untouched.
Also, typically compose automatically creates a network where all the containing services of that stack communicate. Separating the compose files help to isolate them a little bit with the default settings.
Aren’t containers the product of compose files? i.e. the compose files spin up containers. I understand the architecture, I’m just not sure about how docker streamlines separate containers running the same process (eg, mysql).
I’m getting some answers saying that it deduplicates, and others saying that it doesn’t. It looks more likely that it’s the former though.
