[SVLS-8757] Add instance enhanced metric in Azure Functions (#114)

* Create datadog-metrics-collector crate to collect instance value with tags

* Categorize metrics with azure.functions prefix as enhanced metrics

* Use metrics collector in main loop and refactor start_dogstatsd

* Change instance metric collection interval to 3, update comments

* Add precondition for enhanced metrics collector in tokio select loop

* Precompute tags in new() rather than building them in collect_and_submit(), change missing instance log to warn

* Resolve instance ID based on hosting plan

* Add unit test for Windows fallback

* Use Tag::new() from libdd_common, make unknown a constant

* Refactor build_enhanced_metrics_tags and add unit tests for build_tags

* Rename Azure-specific files

* Add unit tests for starting metrics components

* Couple metrics aggregator and flusher together

* Add clarifying comment

* nit: fix formatting and Cargo.lock

* Update datadog-metrics-collector libdatadog rev to d7eef8031192d0ee79ba64cd824804c5a57abacf

Author: kathiehuang

Cargo.lock

@@ -0,0 +1,11 @@
+[package]
+name = "datadog-metrics-collector"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+description = "Collector to read, compute, and submit enhanced metrics in Serverless environments"
+
+[dependencies]
+dogstatsd = { path = "../dogstatsd", default-features = true }
+tracing = { version = "0.1", default-features = false }
+libdd-common = { git = "https://github.com/DataDog/libdatadog", rev = "d7eef8031192d0ee79ba64cd824804c5a57abacf", default-features = false }

crates/datadog-metrics-collector/Cargo.toml

@@ -0,0 +1,176 @@
+// Copyright 2023-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
+//! Instance identity metric collector for Azure Functions.
+//!
+//! Submits `azure.functions.enhanced.instance` with value 1.0 on each
+//! collection tick, tagged with the instance identifier.
+
+use dogstatsd::aggregator::AggregatorHandle;
+use dogstatsd::metric::{Metric, MetricValue, SortedTags};
+use std::env;
+use tracing::{error, warn};
+
+const INSTANCE_METRIC: &str = "azure.functions.enhanced.instance";
+
+/// Resolves the instance ID from explicit values (used by tests).
+///
+/// Picks the env var that matches the Azure integration metric's `instance`
+/// tag for the current hosting plan with fallback logic
+/// if the preferred source is empty.
+fn resolve_instance_id_from(
+    website_sku: Option<&str>,
+    container_name: Option<&str>,
+    website_pod_name: Option<&str>,
+    computer_name: Option<&str>,
+) -> Option<String> {
+    fn non_empty(s: Option<&str>) -> Option<&str> {
+        s.filter(|v| !v.is_empty())
+    }
+
+    let sku_preferred = match website_sku {
+        Some("FlexConsumption") | Some("Dynamic") => {
+            non_empty(container_name).or(non_empty(website_pod_name))
+        }
+        Some(_) => non_empty(computer_name),
+        None => None,
+    };
+
+    sku_preferred
+        .or_else(|| non_empty(container_name))
+        .or_else(|| non_empty(website_pod_name))
+        .or_else(|| non_empty(computer_name))
+        .map(|s| s.to_lowercase())
+}
+
+/// Resolves the instance ID from environment variables.
+fn resolve_instance_id() -> Option<String> {
+    resolve_instance_id_from(
+        env::var("WEBSITE_SKU").ok().as_deref(),
+        env::var("CONTAINER_NAME").ok().as_deref(),
+        env::var("WEBSITE_POD_NAME").ok().as_deref(),
+        env::var("COMPUTERNAME").ok().as_deref(),
+    )
+}
+
+pub struct InstanceMetricsCollector {
+    aggregator: AggregatorHandle,
+    tags: Option<SortedTags>,
+}
+
+impl InstanceMetricsCollector {
+    /// Creates a new collector, returning `None` if no instance ID is found.
+    pub fn new(aggregator: AggregatorHandle, tags: Option<SortedTags>) -> Option<Self> {
+        let instance_id = resolve_instance_id();
+        let Some(instance_id) = instance_id else {
+            warn!("No instance ID found, instance metric will not be submitted");
+            return None;
+        };
+
+        // Precompute tags: enhanced metrics tags + instance tag
+        let instance_tag = format!("instance:{}", instance_id);
+        let tags = match tags {
+            Some(mut existing) => {
+                if let Ok(id_tag) = SortedTags::parse(&instance_tag) {
+                    existing.extend(&id_tag);
+                }
+                Some(existing)
+            }
+            None => SortedTags::parse(&instance_tag).ok(),
+        };
+
+        Some(Self { aggregator, tags })
+    }
+
+    pub fn collect_and_submit(&self) {
+        let metric = Metric::new(
+            INSTANCE_METRIC.into(),
+            MetricValue::gauge(1.0),
+            self.tags.clone(),
+            None,
+        );
+
+        if let Err(e) = self.aggregator.insert_batch(vec![metric]) {
+            error!("Failed to insert instance metric: {}", e);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_flex_consumption_uses_container_name() {
+        let id = resolve_instance_id_from(
+            Some("FlexConsumption"),
+            Some("0--abc-DEF"),
+            Some("0--abc-DEF"),
+            None,
+        );
+        assert_eq!(id, Some("0--abc-def".to_string()));
+    }
+
+    #[test]
+    fn test_flex_consumption_falls_back_to_pod_name_if_container_missing() {
+        let id = resolve_instance_id_from(Some("FlexConsumption"), None, Some("pod-XYZ"), None);
+        assert_eq!(id, Some("pod-xyz".to_string()));
+    }
+
+    #[test]
+    fn test_consumption_uses_container_name() {
+        let id = resolve_instance_id_from(
+            Some("Dynamic"),
+            Some("ABCD1234-111122223333444455"),
+            None,
+            None,
+        );
+        assert_eq!(id, Some("abcd1234-111122223333444455".to_string()));
+    }
+
+    #[test]
+    fn test_elastic_premium_uses_computer_name() {
+        let id =
+            resolve_instance_id_from(Some("ElasticPremium"), None, None, Some("ep0fakewk0000A1"));
+        assert_eq!(id, Some("ep0fakewk0000a1".to_string()));
+    }
+
+    #[test]
+    fn test_dedicated_uses_computer_name() {
+        let id = resolve_instance_id_from(Some("PremiumV3"), None, None, Some("p3fakewk0000B2"));
+        assert_eq!(id, Some("p3fakewk0000b2".to_string()));
+    }
+
+    #[test]
+    fn test_empty_string_is_treated_as_missing() {
+        let id =
+            resolve_instance_id_from(Some("ElasticPremium"), Some(""), Some(""), Some("worker-1"));
+        assert_eq!(id, Some("worker-1".to_string()));
+    }
+
+    #[test]
+    fn test_unknown_sku_falls_back_to_search_order() {
+        let id = resolve_instance_id_from(Some("SomeNewSku"), Some("container-1"), None, None);
+        assert_eq!(id, Some("container-1".to_string()));
+    }
+
+    #[test]
+    fn test_missing_sku_falls_back_to_search_order() {
+        let id = resolve_instance_id_from(None, Some("container-1"), None, Some("worker-1"));
+        assert_eq!(id, Some("container-1".to_string()));
+    }
+
+    #[test]
+    fn test_no_env_vars_returns_none() {
+        let id = resolve_instance_id_from(None, None, None, None);
+        assert_eq!(id, None);
+    }
+
+    // On Windows Consumption we've observed CONTAINER_NAME and WEBSITE_POD_NAME
+    // unset but COMPUTERNAME set
+    #[test]
+    fn test_windows_consumption_falls_through_to_computer_name() {
+        let id = resolve_instance_id_from(Some("Dynamic"), None, None, Some("10-20-30-40"));
+        assert_eq!(id, Some("10-20-30-40".to_string()));
+    }
+}

crates/datadog-metrics-collector/src/azure_instance.rs

@@ -0,0 +1,123 @@
+// Copyright 2023-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
+//! Shared tag builder for enhanced metrics.
+//!
+//! Tags are attached to all enhanced metrics submitted by the metrics collector.
+
+use dogstatsd::metric::SortedTags;
+use libdd_common::{azure_app_services, tag::Tag};
+use std::env;
+use tracing::warn;
+
+/// `libdd_common::azure_app_services` returns this value when the corresponding Azure metadata isn't populated.
+const AAS_UNKNOWN_VALUE: &str = "unknown";
+
+/// Builds the common tags for all enhanced metrics.
+///
+/// Sources:
+/// - Azure metadata (resource_group, subscription_id, name) from libdd_common
+/// - Environment variables (region, plan_tier, service, env, version, serverless_compat_version)
+///
+/// The DogStatsD origin tag (e.g. `origin:azurefunction`) is added by the metrics aggregator,
+/// not here.
+pub fn build_enhanced_metrics_tags() -> Option<SortedTags> {
+    let mut pairs: Vec<(&'static str, String)> = Vec::new();
+
+    if let Some(aas_metadata) = &*azure_app_services::AAS_METADATA_FUNCTION {
+        for (name, value) in [
+            ("resource_group", aas_metadata.get_resource_group()),
+            ("subscription_id", aas_metadata.get_subscription_id()),
+            ("name", aas_metadata.get_site_name()),
+        ] {
+            if value != AAS_UNKNOWN_VALUE {
+                pairs.push((name, value.to_string()));
+            }
+        }
+    }
+
+    for (tag_name, env_var) in [
+        ("region", "REGION_NAME"),
+        ("plan_tier", "WEBSITE_SKU"),
+        ("service", "DD_SERVICE"),
+        ("env", "DD_ENV"),
+        ("version", "DD_VERSION"),
+        ("serverless_compat_version", "DD_SERVERLESS_COMPAT_VERSION"),
+    ] {
+        if let Ok(val) = env::var(env_var) {
+            pairs.push((tag_name, val));
+        }
+    }
+
+    build_tags(pairs)
+}
+
+fn build_tags(pairs: impl IntoIterator<Item = (&'static str, String)>) -> Option<SortedTags> {
+    let mut tags: Vec<Tag> = Vec::new();
+    for (key, value) in pairs {
+        if value.is_empty() {
+            continue;
+        }
+        // Tag::new validates the combined "key:value" string: it must be
+        // non-empty and not start or end with a colon
+        match Tag::new(key, &value) {
+            Ok(t) => tags.push(t),
+            Err(e) => warn!("Skipping invalid tag {key}:{value}: {e}"),
+        }
+    }
+    if tags.is_empty() {
+        return None;
+    }
+    let joined = tags
+        .iter()
+        .map(|t| t.as_ref())
+        .collect::<Vec<&str>>()
+        .join(",");
+    SortedTags::parse(&joined).ok()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_build_tags_returns_none_when_no_pairs() {
+        let pairs: Vec<(&'static str, String)> = Vec::new();
+        assert!(build_tags(pairs).is_none());
+    }
+
+    #[test]
+    fn test_build_tags_returns_none_when_all_values_empty() {
+        let pairs = vec![("service", String::new()), ("env", String::new())];
+        assert!(build_tags(pairs).is_none());
+    }
+
+    #[test]
+    fn test_build_tags_skips_empty_values() {
+        let pairs = vec![("service", String::new()), ("env", "dev".to_string())];
+        let tags = build_tags(pairs).unwrap().to_strings();
+        assert_eq!(tags, vec!["env:dev"]);
+    }
+
+    #[test]
+    fn test_build_tags_includes_all_nonempty_pairs() {
+        let pairs = vec![
+            ("service", "svc-1".to_string()),
+            ("env", "dev".to_string()),
+            ("version", "1.2.3".to_string()),
+        ];
+        let mut tags = build_tags(pairs).unwrap().to_strings();
+        tags.sort();
+        assert_eq!(tags, vec!["env:dev", "service:svc-1", "version:1.2.3"]);
+    }
+
+    #[test]
+    fn test_build_tags_rejects_trailing_colon_values() {
+        let pairs = vec![
+            ("service", "svc-1:".to_string()),
+            ("env", "dev".to_string()),
+        ];
+        let tags = build_tags(pairs).unwrap().to_strings();
+        assert_eq!(tags, vec!["env:dev"]);
+    }
+}

crates/datadog-metrics-collector/src/azure_tags.rs

@@ -0,0 +1,11 @@
+// Copyright 2023-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
+#![cfg_attr(not(test), deny(clippy::panic))]
+#![cfg_attr(not(test), deny(clippy::unwrap_used))]
+#![cfg_attr(not(test), deny(clippy::expect_used))]
+#![cfg_attr(not(test), deny(clippy::todo))]
+#![cfg_attr(not(test), deny(clippy::unimplemented))]
+
+pub mod azure_instance;
+pub mod azure_tags;

crates/datadog-metrics-collector/src/lib.rs

@@ -11,6 +11,7 @@ windows-pipes = ["datadog-trace-agent/windows-pipes", "dogstatsd/windows-pipes"]
 
 [dependencies]
 datadog-logs-agent = { path = "../datadog-logs-agent" }
+datadog-metrics-collector = { path = "../datadog-metrics-collector" }
 datadog-trace-agent = { path = "../datadog-trace-agent" }
 libdd-trace-utils = { git = "https://github.com/DataDog/libdatadog", rev = "d7eef8031192d0ee79ba64cd824804c5a57abacf" }
 datadog-fips = { path = "../datadog-fips", default-features = false }