feat/openadr3_1_mdns by Jagaskak · Pull Request #367 · OpenLEADR/openleadr-rs

Jagaskak · 2026-02-11T22:16:35Z

Summary

Implements mDNS service discovery for VTN servers (resolves #276) with corresponding client-side discovery capabilities.
Implement mDNS in VTN for and an example implementation of VTN discovery for the client.

Details

VTN Changes

mDNS Service Registration: VTN advertises itself via mDNS on startup
- Service type: _openadr-http._tcp.local.
- Service metadata: OpenADR version (3.1) and API path (/programs)
- Configurable via environment variables (see .env)
Refactored server creation to make more accessible for testing

Client Changes

mDNS discovery implementation in openleadr-client/mdns.rs
- Searches for VTN services on local network
- Returns list of discovered VTNs
Example implementation in examples/discover_vtns.rs

Testing

Added a unit test for VTN implementation
Added integration test to test broadcast and discovery between VTN and VEN

Limitations

In environments with many virtual networking interfaces, explicit configuration of IP Address is needed
Discovery timeout is hardcoded to 20 seconds in the client

Signed-off-by: Akshaya Jagannadharao <[email protected]>

codecov · 2026-02-13T08:43:12Z

Codecov Report

❌ Patch coverage is 96.03175% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.82%. Comparing base (a39857b) to head (fbf04ec).
⚠️ Report is 4 commits behind head on openadr3_1.

Files with missing lines	Patch %	Lines
openleadr-vtn/src/main.rs	0.00%	3 Missing ⚠️
openleadr-client/src/mdns.rs	94.73%	1 Missing ⚠️
openleadr-vtn/src/lib.rs	97.05%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##           openadr3_1     #367      +/-   ##
==============================================
+ Coverage       80.07%   80.82%   +0.75%     
==============================================
  Files              41       44       +3     
  Lines            4898     5013     +115     
==============================================
+ Hits             3922     4052     +130     
+ Misses            976      961      -15

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pohlm01

Thanks a lot for your PR! As mentioned, it runs on my machine, which is great. I still found a couple of points that could use some improvement. Let me know if you could use any help.

pohlm01 · 2026-02-13T08:40:42Z

openleadr-client/examples/discover_vtns.rs

+async fn main() {
+    info!("Searching for VTN servers...");
+
+    let vtns = discover_local_vtns("_openadr-http._tcp.local.").await;


According to the spec, this should be _openadr3._tcp.local., shouldn't it? (Also see various other places in the code)

https://github.com/oadr3-org/specification/blob/main/3.1.1/Definition.md#discovery-and-configuration-of-local-vtns

pohlm01 · 2026-02-13T08:47:45Z

openleadr-client/src/mdns.rs

+    let timeout = tokio::time::sleep(std::time::Duration::from_secs(20));
+    tokio::pin!(timeout);


Maybe move the sleep in the loop. I think that would look cleaner to me, and you can skip the pin!. Additionally, it might be nice to add two more parameters to the function:

The maximum time you want to search, i.e., the timeout

An optional limit of VTNs to discover. I imagine most users want to discover only a single VTN and immediately return as soon as it's found instead of waiting for the full timeout.

pohlm01 · 2026-02-13T08:58:03Z

openleadr-vtn/src/mdns.rs

+    let mdns = ServiceDaemon::new().expect("Failed to create daemon");
+
+    // Include metadata about the VTN service, such as version and API path
+    let properties = [("version", "3.1"), ("path", "/programs")];


I think you should double-check that with the spec:

The version has three parts, i.e, 3.1.0

The path isn't a property that's specified

base_path is missing

local_url is missing

We might want to skip proram_names, requires_auth, and openapi_url for now. Especially the program_names seem like a challenge to me, as it changes over the curse of the VTN lifetime.

pohlm01 · 2026-02-13T08:59:51Z

openleadr-vtn/src/mdns.rs

+
+        // Search for the ServiceResolved event, timeout after 5 seconds if not found
+        let mut found = false;
+        let timeout = tokio::time::sleep(Duration::from_secs(5));


Moving the sleep right into the select! branch seems cleaner to me

pohlm01 · 2026-02-13T09:00:37Z

openleadr-vtn/src/mdns.rs

+            }
+        }
+
+        assert!(found, "The mDNS service was not discovered within the 5s timeout.");


nitpik: The timeout is 0.5s

pohlm01 · 2026-02-13T09:12:51Z

openleadr-vtn/tests/mdns_integration_test.rs

+    std::env::set_var("PORT", "3999"); // Random port
+    std::env::set_var("MDNS_SERVICE_TYPE", "_openadr-test._tcp.local.");
+    std::env::set_var("MDNS_SERVER_NAME", "test-vtn-integration");
+    std::env::set_var("MDNS_IP_ADDRESS", "127.0.0.1");


Unfortunately, set_var is marked unsafe from the 2024 edition onwards (and was already unsafe before, but the marking was missing). We have an outstanding issue to migrate to the 2024 edition that's currently blocked by other tests that also use the set_var function.
Maybe you can find a way to either make sure the usage of unsafe is fine here and mark it as such (with an explanation), or avoid the set_var function. I haven't looked into this myself now, so I don't know what the best solution from the top of my head, but let me know if you could use any assistance.

pohlm01 · 2026-02-13T09:14:55Z

openleadr-client/src/mdns.rs

+                    if let Some(host) = info.get_addresses().iter().next() {
+                        let port = info.get_port();
+                        if let Ok(url) = url::Url::parse(&format!("http://{}:{}", host, port)) {
+                            found_urls.push(url);
+                        }


I don't think we gain a lot from formatting the url here. Instead, I think we should return a struct with all the information we can get from the announcement (version, base_path, local_url, etc.).

pohlm01 · 2026-02-13T10:12:13Z

Also, please make sure to run cargo fmt and fix the Clippy issues. The "Audit dependencies" failure should be solved if you merge the latest changes from the openadr3_1 branch.

Jagaskak added 10 commits February 11, 2026 13:20

mdns used, tests pass

992aba8

Signed-off-by: Akshaya Jagannadharao <[email protected]>

unit test for mdns

5441e3c

Signed-off-by: Akshaya Jagannadharao <[email protected]>

pull mdns vars from .env

01f3a12

Signed-off-by: Akshaya Jagannadharao <[email protected]>

removed automatic ip discovery and created client example of using mdns

233a0f8

Signed-off-by: Akshaya Jagannadharao <[email protected]>

pull out server creation and implement integration test

85e9fb6

Signed-off-by: Akshaya Jagannadharao <[email protected]>

move test to openleadr-vtn

76bbab1

Signed-off-by: Akshaya Jagannadharao <[email protected]>

fix lib imports

c5e1f73

Signed-off-by: Akshaya Jagannadharao <[email protected]>

reset VTN PORT in env file

2d9e11d

Signed-off-by: Akshaya Jagannadharao <[email protected]>

new lines at EOF

4bbfbd9

Signed-off-by: Akshaya Jagannadharao <[email protected]>

switch prints to traces

fbf04ec

Signed-off-by: Akshaya Jagannadharao <[email protected]>

pohlm01 self-requested a review February 13, 2026 08:34

pohlm01 assigned Jagaskak Feb 13, 2026

pohlm01 linked an issue Feb 13, 2026 that may be closed by this pull request

mDNS for finding local VTNs #276

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pohlm01 reviewed Feb 13, 2026

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feat/openadr3_1_mdns#367

feat/openadr3_1_mdns#367
Jagaskak wants to merge 10 commits intoOpenLEADR:openadr3_1from
Jagaskak:feat/openadr3_1_mdns

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		let timeout = tokio::time::sleep(std::time::Duration::from_secs(20));
		tokio::pin!(timeout);

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Summary

Details

VTN Changes

Client Changes

Testing

Limitations

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