feature: add global labels and namespace support for dogstatsd exporter (#555)

Author: nappairam

metrics-exporter-dogstatsd/src/builder.rs

@@ -1,5 +1,6 @@
 use std::{fmt, net::SocketAddr, sync::Arc, time::Duration};
 
+use metrics::Label;
 use thiserror::Error;
 use tracing::debug;
 
@@ -97,6 +98,8 @@ pub struct DogStatsDBuilder {
     histogram_sampling: bool,
     histogram_reservoir_size: usize,
     histograms_as_distributions: bool,
+    global_labels: Vec<Label>,
+    global_prefix: Option<String>,
 }
 
 impl DogStatsDBuilder {
@@ -229,6 +232,29 @@ impl DogStatsDBuilder {
         self
     }
 
+    /// Set Global labels for all metrics to this exporter
+    ///
+    /// Global labels are applied to all metrics.
+    #[must_use]
+    pub fn with_global_labels(mut self, labels: Vec<Label>) -> Self {
+        self.global_labels = labels;
+        self
+    }
+
+    /// Adds a global prefix for every metric name.
+    ///
+    /// Global prefix is applied to all metrics. Its intended use is to introduce a configurable
+    /// namespace for every metric generated by the application such that different deployments
+    /// can operate on their own family of metrics without overlap.
+    #[must_use]
+    pub fn set_global_prefix<P>(mut self, prefix: P) -> Self
+    where
+        P: Into<String>,
+    {
+        self.global_prefix = Some(prefix.into());
+        self
+    }
+
     /// Sets whether or not to enable telemetry for the exporter.
     ///
     /// When enabled, additional metrics will be sent to the configured remote server that provide insight into the
@@ -321,6 +347,8 @@ impl DogStatsDBuilder {
             histogram_sampling: self.histogram_sampling,
             histogram_reservoir_size: self.histogram_reservoir_size,
             histograms_as_distributions: self.histograms_as_distributions,
+            global_labels: self.global_labels,
+            global_prefix: self.global_prefix,
         };
 
         let state = Arc::new(State::new(state_config));
@@ -387,6 +415,8 @@ impl Default for DogStatsDBuilder {
             histogram_sampling: false,
             histogram_reservoir_size: DEFAULT_HISTOGRAM_RESERVOIR_SIZE,
             histograms_as_distributions: true,
+            global_labels: Vec::default(),
+            global_prefix: Option::default(),
         }
     }
 }

metrics-exporter-dogstatsd/src/state.rs

@@ -1,6 +1,6 @@
 use std::{collections::HashSet, time::SystemTime};
 
-use metrics::Key;
+use metrics::{Key, Label};
 use metrics_util::registry::Registry;
 use tracing::error;
 
@@ -27,6 +27,12 @@ pub struct StateConfiguration {
 
     /// Whether or not to emit histograms as distributions.
     pub histograms_as_distributions: bool,
+
+    /// Global labels to add to all metrics
+    pub global_labels: Vec<Label>,
+
+    /// Global prefix/namespace to use for all metrics
+    pub global_prefix: Option<String>,
 }
 
 /// Exporter state.
@@ -96,7 +102,19 @@ impl State {
 
             active_counters += 1;
 
-            let result = writer.write_counter(&key, value, self.get_aggregation_timestamp());
+            let prefix = if key.name().starts_with("datadog.dogstatsd.client") {
+                None
+            } else {
+                self.config.global_prefix.as_deref()
+            };
+
+            let result = writer.write_counter(
+                &key,
+                value,
+                self.get_aggregation_timestamp(),
+                prefix,
+                &self.config.global_labels,
+            );
             if result.any_failures() {
                 let points_dropped = result.points_dropped();
                 error!(
@@ -117,7 +135,18 @@ impl State {
 
         for (key, gauge) in gauges {
             let (value, points_flushed) = gauge.flush();
-            let result = writer.write_gauge(&key, value, self.get_aggregation_timestamp());
+            let prefix = if key.name().starts_with("datadog.dogstatsd.client") {
+                None
+            } else {
+                self.config.global_prefix.as_deref()
+            };
+            let result = writer.write_gauge(
+                &key,
+                value,
+                self.get_aggregation_timestamp(),
+                prefix,
+                &self.config.global_labels,
+            );
             if result.any_failures() {
                 let points_dropped = result.points_dropped();
                 error!(metric_name = key.name(), points_dropped, "Failed to build gauge payload.");
@@ -137,13 +166,30 @@ impl State {
             }
 
             active_histograms += 1;
+            let prefix = if key.name().starts_with("datadog.dogstatsd.client") {
+                None
+            } else {
+                self.config.global_prefix.as_deref()
+            };
 
             histogram.flush(|maybe_sample_rate, values| {
                 let points_len = values.len();
                 let result = if self.config.histograms_as_distributions {
-                    writer.write_distribution(&key, values, maybe_sample_rate)
+                    writer.write_distribution(
+                        &key,
+                        values,
+                        maybe_sample_rate,
+                        prefix,
+                        &self.config.global_labels,
+                    )
                 } else {
-                    writer.write_histogram(&key, values, maybe_sample_rate)
+                    writer.write_histogram(
+                        &key,
+                        values,
+                        maybe_sample_rate,
+                        prefix,
+                        &self.config.global_labels,
+                    )
                 };
 
                 // Scale the points flushed/dropped values by the sample rate to determine the true number of points flushed/dropped.