fix(obs): distinguish metrics by process identity (#8343)

Attach process.pid to the OpenTelemetry resource and promote it for Prometheus
so counter series from restarted processes remain distinct. Preserve the stable
RustFS node and service instance attributes.

Co-authored-by: heihutu <heihutu@gmail.com>
Co-authored-by: zhi22915 <qiuzgang@gmail.com>

.docker/observability/prometheus.yml

@@ -61,6 +61,7 @@ scrape_configs:
 otlp:
   promote_resource_attributes:
     - service.instance.id
+    - process.pid
     - service.name
     - service.namespace
     - cloud.availability_zone

crates/obs/src/telemetry/resource.rs

@@ -16,9 +16,9 @@
 //!
 //! A `Resource` describes the entity producing telemetry data.  The resource
 //! built here includes the service name, service version, deployment
-//! environment, the stable RustFS node identity, and the local machine IP
-//! address so that data can be correlated across services in a distributed
-//! system.
+//! environment, the stable RustFS node identity, the process ID, and the local
+//! machine IP address so telemetry series can be correlated across service
+//! restarts and nodes.
 
 use crate::config::OtelConfig;
 use crate::node_identity::{RUSTFS_NODE_ATTRIBUTE, local_node_identity};
@@ -27,7 +27,7 @@ use opentelemetry_sdk::Resource;
 use opentelemetry_semantic_conventions::{
     SCHEMA_URL,
     attribute::{
-        DEPLOYMENT_ENVIRONMENT_NAME, NETWORK_LOCAL_ADDRESS, SERVICE_INSTANCE_ID as OTEL_SERVICE_INSTANCE_ID,
+        DEPLOYMENT_ENVIRONMENT_NAME, NETWORK_LOCAL_ADDRESS, PROCESS_PID, SERVICE_INSTANCE_ID as OTEL_SERVICE_INSTANCE_ID,
         SERVICE_VERSION as OTEL_SERVICE_VERSION,
     },
 };
@@ -48,6 +48,8 @@ use std::borrow::Cow;
 /// - `network.local.address` — the primary local IP of the current host,
 ///   useful as an operational fallback when the stable node name is not yet
 ///   initialized.
+/// - `process.pid` — distinguishes telemetry emitted by different processes
+///   running on the same node.
 ///
 /// All attributes are attached to the resource using the semantic conventions
 /// schema URL to ensure compatibility with standard OTLP backends.
@@ -70,6 +72,7 @@ pub(super) fn build_resource(config: &OtelConfig) -> Resource {
                 KeyValue::new(RUSTFS_NODE_ATTRIBUTE, node_identity.clone()),
                 KeyValue::new(OTEL_SERVICE_INSTANCE_ID, node_identity),
                 KeyValue::new(NETWORK_LOCAL_ADDRESS, local_ip),
+                KeyValue::new(PROCESS_PID, i64::from(std::process::id())),
             ],
             SCHEMA_URL,
         )
@@ -101,6 +104,12 @@ mod tests {
                 .map(|value| value.to_string()),
             Some("node1:9000".to_string())
         );
+        assert_eq!(
+            resource
+                .get(&Key::from_static_str(PROCESS_PID))
+                .map(|value| value.to_string()),
+            Some(std::process::id().to_string())
+        );
 
         rustfs_common::set_global_local_node_name(&previous).await;
     }