feat: Add configuration option for metric temporality

Update config file docs to add information about Temporality

Co-authored-by: Dale Seo <[email protected]>

Author: swcollard

.changesets/feat_metric_temporality.md

@@ -0,0 +1,8 @@
+### feat: Add configuration option for metric temporality - @swcollard PR #413
+
+Creates a new configuration option for telemetry to set the Metric temporality to either Cumulative (default) or Delta.
+
+* Cumulative - The metric value will be the overall value since the start of the measurement.
+* Delta - The metric will be the difference in the measurement since the last time it was reported.
+
+Some observability  vendors require that one is used over the other so we want to support the configuration in the MCP Server.

crates/apollo-mcp-server/src/runtime/telemetry.rs

@@ -7,7 +7,7 @@ use crate::runtime::telemetry::sampler::SamplerOption;
 use apollo_mcp_server::generated::telemetry::TelemetryAttribute;
 use opentelemetry::{Key, KeyValue, global, trace::TracerProvider as _};
 use opentelemetry_otlp::WithExportConfig;
-use opentelemetry_sdk::metrics::{Instrument, Stream};
+use opentelemetry_sdk::metrics::{Instrument, Stream, Temporality};
 use opentelemetry_sdk::{
     Resource,
     metrics::{MeterProviderBuilder, PeriodicReader, SdkMeterProvider},
@@ -44,17 +44,38 @@ pub struct MetricsExporters {
     omitted_attributes: Option<HashSet<TelemetryAttribute>>,
 }
 
+#[derive(Debug, Deserialize, JsonSchema)]
+pub enum MetricTemporality {
+    Cumulative,
+    Delta,
+}
+
+impl OTLPMetricExporter {
+    pub fn to_temporality(&self) -> Temporality {
+        match self
+            .temporality
+            .as_ref()
+            .unwrap_or(&MetricTemporality::Cumulative)
+        {
+            MetricTemporality::Cumulative => Temporality::Cumulative,
+            MetricTemporality::Delta => Temporality::Delta,
+        }
+    }
+}
+
 #[derive(Debug, Deserialize, JsonSchema)]
 pub struct OTLPMetricExporter {
     endpoint: String,
     protocol: String,
+    temporality: Option<MetricTemporality>,
 }
 
 impl Default for OTLPMetricExporter {
     fn default() -> Self {
         Self {
             endpoint: "http://localhost:4317".into(),
             protocol: "grpc".into(),
+            temporality: Some(MetricTemporality::Cumulative),
         }
     }
 }
@@ -122,10 +143,12 @@ fn init_meter_provider(telemetry: &Telemetry) -> Result<SdkMeterProvider, anyhow
         "grpc" => opentelemetry_otlp::MetricExporter::builder()
             .with_tonic()
             .with_endpoint(otlp.endpoint.clone())
+            .with_temporality(otlp.to_temporality())
             .build()?,
         "http/protobuf" => opentelemetry_otlp::MetricExporter::builder()
             .with_http()
             .with_endpoint(otlp.endpoint.clone())
+            .with_temporality(otlp.to_temporality())
             .build()?,
         other => {
             return Err(anyhow::anyhow!(
@@ -331,6 +354,7 @@ mod tests {
                 otlp: Some(OTLPMetricExporter {
                     protocol: "bogus".to_string(),
                     endpoint: "http://localhost:4317".to_string(),
+                    temporality: None,
                 }),
                 omitted_attributes: None,
             }),
@@ -354,6 +378,7 @@ mod tests {
                 otlp: Some(OTLPMetricExporter {
                     protocol: "http/protobuf".to_string(),
                     endpoint: "http://localhost:4318/v1/metrics".to_string(),
+                    temporality: Some(MetricTemporality::Delta),
                 }),
                 omitted_attributes: None,
             }),

docs/source/config-file.mdx

@@ -244,20 +244,29 @@ transport:
 
 #### Metrics
 
-| Option                | Type             | Default                     | Description                                    |
-| :-------------------- | :--------------- | :-------------------------- | :--------------------------------------------- |
-| `otlp`                | `OTLP Exporter`  | `null` (Exporting disabled) | Configuration for exporting metrics via OTLP.  |
-| `omitted_attributes`  | `List<String>`   |                             | List of attributes to be omitted from metrics. |
+| Option                | Type                    | Default                     | Description                                    |
+| :-------------------- | :---------------------- | :-------------------------- | :--------------------------------------------- |
+| `otlp`                | `OTLP Metric Exporter`  | `null` (Exporting disabled) | Configuration for exporting metrics via OTLP.  |
+| `omitted_attributes`  | `List<String>`          |                             | List of attributes to be omitted from metrics. |
+
+
+#### OTLP Metrics Exporter
+
+| Option        | Type                                     | Default                  | Description                                                                                                                                                                                             |
+| :---------    | :--------------------------------------- | :----------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
+| `endpoint`    | `URL`                                    | `http://localhost:4137`  | URL to export data to. Requires full path.                                                                                                                                                              |
+| `protocol`    | `string`                                 | `grpc`                   | Protocol for export. Only `grpc` and `http/protobuf` are supported.                                                                                                                                     |
+| `temporality` | `MetricTemporality` | `Cumulative`             | Optional OTel property that refers to the way additive quantities are expressed, in relation to time, indicating whether reported values incorporate previous measurements (Cumulative) or not (Delta). |
 
 #### Traces
 
-| Option                | Type             | Default                     | Description                                    |
-| :-------------------- | :--------------- | :-------------------------- | :--------------------------------------------- |
-| `otlp`                | `OTLP Exporter`  | `null` (Exporting disabled) | Configuration for exporting traces via OTLP.   |
-| `sampler`             | `SamplerOption`  | `ALWAYS_ON`                 | Configuration to control sampling of traces.   |
-| `omitted_attributes`  | `List<String>`   |                             | List of attributes to be omitted from traces. |
+| Option                | Type                   | Default                     | Description                                    |
+| :-------------------- | :--------------------- | :-------------------------- | :--------------------------------------------- |
+| `otlp`                | `OTLP Trace Exporter`  | `null` (Exporting disabled) | Configuration for exporting traces via OTLP.   |
+| `sampler`             | `SamplerOption`        | `ALWAYS_ON`                 | Configuration to control sampling of traces.   |
+| `omitted_attributes`  | `List<String>`         |                             | List of attributes to be omitted from traces.  |
 
-#### OTLP Exporter
+#### OTLP Trace Exporter
 
 | Option      | Type      | Default                     | Description                                                      |
 | :---------  | :-------- | :-------------------------- | :--------------------------------------------------------------- |