Vali, a C Library for Varlink

Posted3 months agoActive3 months ago

GalaxySnail

43 points

15 comments

emersion.frTechstory

supportivepositive

Debate

20/100

C LibraryVarlinkSystem Programming

Key topics

C Library

Varlink

System Programming

The announcement of Vali, a C library for Varlink, has been met with interest and support from the HN community, with discussions focusing on the library's design and potential applications.

Snapshot generated from the HN discussion

Discussion Activity

Active discussion

First comment

Peak period

84-96h

Avg / period

Comment distribution15 data points

Loading chart...

Based on 15 loaded comments

Key moments

01Story posted
Oct 10, 2025 at 9:13 AM EDT
3 months ago
Step 01
02First comment
Oct 14, 2025 at 1:04 AM EDT
4d after posting
Step 02
03Peak activity
11 comments in 84-96h
Hottest window of the conversation
Step 03
04Latest activity
Oct 15, 2025 at 8:47 PM EDT
3 months ago
Step 04

Generating AI Summary...

Analyzing up to 500 comments to identify key contributors and discussion patterns

Discussion (15 comments)

Showing 15 comments

NewJazz

3 months ago

1 reply

What does varlink do that grpc or capnproto don't offer? Hell, it doesn't even seem much batter than openapi...

emersion

3 months ago

2 replies

The main use-case is different: gRPC and Cap'n'Proto are designed for networked servers, while D-Bus and Varlink are designed for local IPC. Varlink is a lot simpler than other alternatives.

sam_bristow

3 months ago

2 replies

I've only had a cursory look at Varlink, but it almost felt too simple. In particular the lack of unsigned or sized integers.

This might enf up being be fine, but it gave me pause when I looked at it previously.

wolletd

3 months ago

1 reply

It's JSON with some simple idea of RPC added to it. With the main idea apparently being that it is human-readable.

We've been using Varlink for one project, but I've never found myself in a situation where I had any benefit from the data being JSON. You rarely read the raw data. But compared to gRPC or CapnProto, you lost compile-time type checking and now you need 10mins of testing a vending machine before you get a "key not found"-error because you missed one spot on renaming.

Also, I've written varlink-cpp building on asio and nl-json at some point: https://github.com/wolletd/varlink-cpp. But as our varlink usage declined, it never found much usage and isn't maintained.

emersion

3 months ago

"you lost compile-time type checking" makes it sound like you haven't been using code generation? Varlink has an interface definition language which makes everything type-safe.

jauntywundrkind

3 months ago

Varlink exists only to be extremely simple.

The Linux ecosystem was using D-Bus for basically everything. But there was some need for IPC in early boot, before any D-Bus brokers were started.

Varlink was the answer, as a simple direct (vs DBus's broker mediated) IPC.

NewJazz

3 months ago

Simpler is pretty subjective. A lot of people have already ingrained the complexity of grpc and/or capnproto. And more importantly, there are a lot of well maintained libraries for those protocols.

At the end of the day, local or remote, it is all just pushing data over sockets, no?

andrewshadura

3 months ago

1 reply

I'm wondering why Varlink, while incredibly similar to JSON-RPC, is designed to be incompatible with it?

NewJazz

3 months ago

Linux people don't want web folks messing with their plumbing is my take lol.

More realistically, adding HTTP where it is not needed adds unnecessary complexity.

burstmode

3 months ago

1 reply

So, there's another copy of CORBA. :-)

guerrilla

3 months ago

That's intentional. That's where this began. GNOME started out by implementing CORBA in a library called ORBit. It was eventually replaced by D-Bus which got more widespread usage across desktop environments and components. Eventually that was adopted at the OS level because of systemd and now they're replacing that with this. So, literally yes.

ongy

3 months ago

Huh, that way of doing asynchronicity is quite interesting.

Though my Haskell and Rust primed brain really dislikes the way ownership of the memory allocation for the response struct works.

It gets allocated by the caller (library), handed over to the function fully owned, and then gets consumed by the response function?

malkia

3 months ago

json, rpc, and that uint64_t bit integer

blixtra

3 months ago

If you want to know more about Varlink, Lennart Poettering gave a talk about it at All Systems Go! last year. https://media.ccc.de/v/all-systems-go-2024-276-varlink-now-/...

sho_hn

3 months ago

Here's a C++/Qt one by KDE hacker David Edmundson: https://blog.davidedmundson.co.uk/blog/introducing-qtvarlink...

View full discussion on Hacker News

ID: 45538628Type: storyLast synced: 11/20/2025, 1:48:02 PM

Want the full context?

Jump to the original sources

Read the primary article or dive into the live Hacker News thread when you're ready.

Open link View on HN