If Linux tried to be an entire computing system all in one code base, (sed, vim, grep, top, etc., etc.) what do you think that would look like code base/maintainability wise? Sounds like a nightmare to me.
The system is defined by a graph of these nodes, since you can pipe messages wherever they're needed; all nodes can be many-many. Each node is a self-contained application which communicates to a master node via tcp/ip (like most pub/sub systems a master node is requried to tell nodes where to send messages). So you can do cool stuff like have lots of seprate networked computers all talking to each other (fairly) easily.
It works pretty well and once you've got a particular node stable - e.g. the node that acquires images - you don't need to touch it. If you need to refactor or bugfix, you only edit that code. If you need to test new things, you can just drop them into an existing system because there's separation between the code (e.g. you just tell the system what your new node will publish/subscribe and it'll do the rest).
There is definitely a feeling of duct tape and glue, since you're often using nodes made by lots of different people, some of which are maintainted, others aren't, different naming conventions, etc. However, I think that's just because ROS is designed to be as generic as possible, rather than a side effect of it running like a microservice.
I get where you are coming from. But you will go async sooner or later if you need any reasonable error recovery or reliability.
The only question is how much pain you will suffer before you do so.
gRPC has no queuing and the connection is held open until the call returns. All of Google's cloud databases are immediately consistent for most operations
But strictly speaking, even inside a single multicore CPU, there is no such thing as immediate consistency. The universe doesn't allow you to update information in two places simultaneously. You can only propagate at the speed of light.
Oh, and the concept of "simultaneous" is suspect too.
Our hardware cousins have striven mightily and mostly successfully for decades to create the illusion that code runs in a Newtonian universe. But it is very much a relativistic one.
You mean like BSD?
Busybox is a slightly better example (even though it’s also a userspace program).
they're part of the same repo and built at the same time than the kernel. Run a big "make universe" here : https://github.com/freebsd/freebsd and see for yourself. That they are different binaries does not matter a lot, it's just a question of user interface. See for instance busybox where all the userspace is in a single binary.
There is the "base" system which is the OS itself and common packages (all the ones you mentioned), then there is the "ports" repo which contains many open-source applications with patches to make them work with OpenBSD.
Here is a Github mirror of their repos: https://github.com/openbsd
I think OpenBSD has reaped many of the same advantages described by Segment with their monorepo approach, such as easily being able to add pledge[1] to many ports relatively quickly.
Also I can pipe these tools together from the same terminal session, like
tail -f foo | grep something | awk ...
Probably one could come up with an abstraction to do Lego with Microservices but we're not there yet.
That's news to me, and seems insane.
Unless you mean "their own database tables", not "database servers". But that's just the same as having multiple directories and files in a Unix filesystem.
If you can afford all your components sharing the same database without creating a big dependency hell, then your problem is _too small_ for microservices.
If your problem is so large that you have to split it up to manage its complexity, start considering microservices (it might still not be the right option for you).
If it could be avoided, these systems were not touched anymore. Instead, other applications where attached to the front and sides.
So I would say: it applies to systems where proper modularization was neglected. In the anecdotical cases I referred to, one major element of this deficiency was a complex database, shared across the whole system.
You would have to have an oddly disconnected schema if modifications to the program don't result in programs accessing parts of the database that other programs are already accessing. If this isn't a problem it means you're using your database as nature intended and letting it provide a language-neutral, shared repository with transactional and consistency guarantees.
so maybe not microservices, but fine nonetheless.
EDIT: two more comments:
- this is exactly what relational databases were designed for. If people can't do this with their micro-services, maybe their choice of database is the issue.
- "micro-service" as the original post suggests, is not synonymous with good. "monolith" is only synonymous with bad because it got run-over by the hype-train. If you have something that works well, be happy. Most people don't.
This video is strangely relevant in this thread... https://www.youtube.com/watch?v=X0tjziAQfNQ
You mean GNU coreutils?