release: WRNexusJS 0.8.0

packages/observability/src/server.ts

@@ -129,4 +129,81 @@ export function createHttpMetricExporter(
   };
 }
 
+export function createOtlpMetricExporter(
+  endpoint: string,
+  options: { headers?: HeadersInit; fetch?: typeof fetch; serviceName?: string } = {},
+): MetricExporter {
+  const send = options.fetch ?? fetch;
+  return {
+    async export(points) {
+      if (!points.length) return;
+      const metrics = points.map((point) => {
+        const attributes = Object.entries(point.labels).map(([key, value]) => ({
+          key,
+          value:
+            typeof value === "boolean"
+              ? { boolValue: value }
+              : typeof value === "number"
+                ? { doubleValue: value }
+                : { stringValue: value },
+        }));
+        const timeUnixNano = String(BigInt(Math.trunc(point.timestamp)) * 1_000_000n);
+        if (point.type === "histogram") {
+          return {
+            name: point.name,
+            histogram: {
+              aggregationTemporality: 2,
+              dataPoints: [
+                {
+                  attributes,
+                  timeUnixNano,
+                  count: String(point.count ?? 0),
+                  sum: point.sum ?? 0,
+                  min: point.min,
+                  max: point.max,
+                  bucketCounts: [String(point.count ?? 0)],
+                  explicitBounds: [],
+                },
+              ],
+            },
+          };
+        }
+        const kind = point.type === "counter" ? "sum" : "gauge";
+        return {
+          name: point.name,
+          [kind]: {
+            ...(kind === "sum" ? { aggregationTemporality: 2, isMonotonic: true } : {}),
+            dataPoints: [{ attributes, timeUnixNano, asDouble: point.value }],
+          },
+        };
+      });
+      const response = await send(endpoint, {
+        method: "POST",
+        headers: {
+          "content-type": "application/json",
+          ...Object.fromEntries(new Headers(options.headers)),
+        },
+        body: JSON.stringify({
+          resourceMetrics: [
+            {
+              resource: {
+                attributes: [
+                  { key: "service.name", value: { stringValue: options.serviceName ?? "wrnexus" } },
+                ],
+              },
+              scopeMetrics: [
+                {
+                  scope: { name: "@wrnexus/observability", version: "0.8.0" },
+                  metrics,
+                },
+              ],
+            },
+          ],
+        }),
+      });
+      if (!response.ok) throw new Error(`OTLP metric export failed with ${response.status}.`);
+    },
+  };
+}
+
 export const defaultMetrics = new MetricsRegistry();