hmon: fix Cargo build, small code changes

Cargo.toml

@@ -6,6 +6,7 @@ members = [
     "src/health_monitoring_lib",
     "examples/rust_supervised_app",
 ]
+default-members = ["src/health_monitoring_lib"]
 
 [workspace.package]
 edition = "2021"

src/health_monitoring_lib/BUILD

@@ -42,6 +42,7 @@ CC_HDRS = [
 rust_library(
     name = "health_monitoring_lib",
     srcs = glob(["rust/**/*.rs"]),
+    crate_features = ["score_supervisor_api_client"],
     crate_root = "rust/lib.rs",
     proc_macro_deps = PROC_MACRO_DEPS,
     visibility = ["//visibility:public"],
@@ -65,6 +66,7 @@ cc_library(
 rust_static_library(
     name = "health_monitoring_lib_ffi",
     srcs = glob(["rust/**/*.rs"]),
+    crate_features = ["score_supervisor_api_client"],
     crate_name = "health_monitoring_lib",
     crate_root = "rust/lib.rs",
     proc_macro_deps = [
@@ -100,6 +102,7 @@ cc_library(
 rust_test(
     name = "tests",
     crate = ":health_monitoring_lib",
+    crate_features = ["stub_supervisor_api_client"],
     rustc_flags = [
         "-C",
         "link-arg=-lm",

src/health_monitoring_lib/Cargo.toml

@@ -7,7 +7,6 @@ edition.workspace = true
 authors.workspace = true
 license-file.workspace = true
 
-
 [lib]
 path = "rust/lib.rs"
 
@@ -18,11 +17,12 @@ workspace = true
 score_log.workspace = true
 score_testing_macros.workspace = true
 containers.workspace = true
-monitor_rs.workspace = true
+monitor_rs = { workspace = true, optional = true }
 
 [dev-dependencies]
 stdout_logger.workspace = true
 
 [features]
-default = []
+default = ["stub_supervisor_api_client"]
 stub_supervisor_api_client = []
+score_supervisor_api_client = ["monitor_rs"]

src/health_monitoring_lib/rust/common.rs

@@ -39,6 +39,9 @@ pub(crate) enum MonitorEvaluationError {
 
 /// Trait for evaluating monitors and reporting errors to be used by HealthMonitor.
 pub(crate) trait MonitorEvaluator {
+    /// Run monitor evaluation.
+    ///
+    /// - `on_error` - error handling, containing tag of failing object and error code.
     fn evaluate(&self, on_error: &mut dyn FnMut(&MonitorTag, MonitorEvaluationError));
 }
 

src/health_monitoring_lib/rust/lib.rs

@@ -15,6 +15,7 @@ mod common;
 mod ffi;
 mod log;
 mod protected_memory;
+mod supervisor_api_client;
 mod tag;
 mod worker;
 
@@ -217,12 +218,13 @@ impl HealthMonitor {
         let monitoring_logic = worker::MonitoringLogic::new(
             monitors,
             self.supervisor_api_cycle,
-            // Currently only `ScoreSupervisorAPIClient` and `StubSupervisorAPIClient` are supported.
-            // The later is meant to be used for testing purposes.
-            #[cfg(not(any(test, feature = "stub_supervisor_api_client")))]
-            worker::ScoreSupervisorAPIClient::new(),
-            #[cfg(any(test, feature = "stub_supervisor_api_client"))]
-            worker::StubSupervisorAPIClient {},
+            #[cfg(all(not(test), feature = "score_supervisor_api_client"))]
+            supervisor_api_client::score_supervisor_api_client::ScoreSupervisorAPIClient::new(),
+            #[cfg(any(
+                test,
+                all(feature = "stub_supervisor_api_client", not(feature = "score_supervisor_api_client"))
+            ))]
+            supervisor_api_client::stub_supervisor_api_client::StubSupervisorAPIClient::new(),
         );
 
         self.worker.start(monitoring_logic)

src/health_monitoring_lib/rust/supervisor_api_client/mod.rs

@@ -0,0 +1,28 @@
+// *******************************************************************************
+// Copyright (c) 2026 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available under the
+// terms of the Apache License Version 2.0 which is available at
+// <https://www.apache.org/licenses/LICENSE-2.0>
+//
+// SPDX-License-Identifier: Apache-2.0
+// *******************************************************************************
+
+//! Module providing [`SupervisorAPIClient`] implementations.
+//! Currently `ScoreSupervisorAPIClient` and `StubSupervisorAPIClient` are supported.
+//! The latter is meant for testing purposes.
+
+/// An abstraction over the API used to notify the supervisor about process liveness.
+pub trait SupervisorAPIClient {
+    fn notify_alive(&self);
+}
+
+// NOTE: various implementations are not mutually exclusive.
+
+#[cfg(feature = "score_supervisor_api_client")]
+pub mod score_supervisor_api_client;
+#[cfg(feature = "stub_supervisor_api_client")]
+pub mod stub_supervisor_api_client;

src/health_monitoring_lib/rust/supervisor_api_client/score_supervisor_api_client.rs

@@ -0,0 +1,40 @@
+// *******************************************************************************
+// Copyright (c) 2026 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available under the
+// terms of the Apache License Version 2.0 which is available at
+// <https://www.apache.org/licenses/LICENSE-2.0>
+//
+// SPDX-License-Identifier: Apache-2.0
+// *******************************************************************************
+
+#![allow(dead_code)]
+
+use crate::log::debug;
+use crate::supervisor_api_client::SupervisorAPIClient;
+use crate::worker::Checks;
+
+pub struct ScoreSupervisorAPIClient {
+    supervisor_link: monitor_rs::Monitor<Checks>,
+}
+
+unsafe impl Send for ScoreSupervisorAPIClient {} // Just assuming it's safe to send across threads, this is a temporary solution
+
+impl ScoreSupervisorAPIClient {
+    pub fn new() -> Self {
+        let value = std::env::var("IDENTIFIER").expect("IDENTIFIER env not set");
+        debug!("ScoreSupervisorAPIClient: Creating with IDENTIFIER={}", value);
+        // This is only temporary usage so unwrap is fine here.
+        let supervisor_link = monitor_rs::Monitor::<Checks>::new(&value).expect("Failed to create supervisor_link");
+        Self { supervisor_link }
+    }
+}
+
+impl SupervisorAPIClient for ScoreSupervisorAPIClient {
+    fn notify_alive(&self) {
+        self.supervisor_link.report_checkpoint(Checks::WorkerCheckpoint);
+    }
+}

src/health_monitoring_lib/rust/supervisor_api_client/stub_supervisor_api_client.rs

@@ -0,0 +1,32 @@
+// *******************************************************************************
+// Copyright (c) 2026 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available under the
+// terms of the Apache License Version 2.0 which is available at
+// <https://www.apache.org/licenses/LICENSE-2.0>
+//
+// SPDX-License-Identifier: Apache-2.0
+// *******************************************************************************
+
+#![allow(dead_code)]
+
+use crate::log::warn;
+use crate::supervisor_api_client::SupervisorAPIClient;
+
+/// A stub implementation of the SupervisorAPIClient that logs alive notifications.
+pub struct StubSupervisorAPIClient;
+
+impl StubSupervisorAPIClient {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl SupervisorAPIClient for StubSupervisorAPIClient {
+    fn notify_alive(&self) {
+        warn!("StubSupervisorAPIClient: notify_alive called");
+    }
+}

src/health_monitoring_lib/rust/tag.rs

@@ -247,13 +247,41 @@ mod tests {
     }
 
     #[test]
-    fn tag_hash() {
-        let example_str = "EXAMPLE";
-        let tag = Tag::from(example_str.to_string());
-        let mut hasher = DefaultHasher::new();
-        tag.hash(&mut hasher);
-        let hash = hasher.finish();
-        assert_eq!(hash, 14738755424381306335);
+    fn tag_hash_is_eq() {
+        let tag1 = Tag::from("same");
+        let hash1 = {
+            let mut hasher = DefaultHasher::new();
+            tag1.hash(&mut hasher);
+            hasher.finish()
+        };
+
+        let tag2 = Tag::from("same");
+        let hash2 = {
+            let mut hasher = DefaultHasher::new();
+            tag2.hash(&mut hasher);
+            hasher.finish()
+        };
+
+        assert_eq!(hash1, hash2);
+    }
+
+    #[test]
+    fn tag_hash_is_ne() {
+        let tag1 = Tag::from("first");
+        let hash1 = {
+            let mut hasher = DefaultHasher::new();
+            tag1.hash(&mut hasher);
+            hasher.finish()
+        };
+
+        let tag2 = Tag::from("second");
+        let hash2 = {
+            let mut hasher = DefaultHasher::new();
+            tag2.hash(&mut hasher);
+            hasher.finish()
+        };
+
+        assert_ne!(hash1, hash2);
     }
 
     #[test]