feat(js): Add OTEL support

js/package.json

@@ -172,7 +172,10 @@
     "zod": "^3.23.8"
   },
   "peerDependencies": {
-    "openai": "*"
+    "openai": "*",
+    "@opentelemetry/api": "^1.9.0",
+    "@opentelemetry/exporter-trace-otlp-proto": "^0.202.0",
+    "@opentelemetry/sdk-trace-base": "^2.0.1"
   },
   "peerDependenciesMeta": {
     "openai": {

js/src/_internal/index.ts

@@ -0,0 +1 @@
+export * from "./otel/index.js";

js/src/_internal/otel/client.ts

@@ -0,0 +1,85 @@
+import { type TracerProvider as OTELTracerProvider } from "@opentelemetry/api";
+import { OTLPTraceExporter } from "@opentelemetry/exporter-trace-otlp-proto";
+import {
+  BatchSpanProcessor,
+  BasicTracerProvider,
+} from "@opentelemetry/sdk-trace-base";
+
+import {
+  getEnvironmentVariable,
+  setEnvironmentVariable,
+} from "../../utils/env.js";
+
+const HAS_OTEL = getEnvironmentVariable("OTEL_ENABLED") === "true";
+
+/**
+ * Convert headers string in format "name=value,name2=value2" to object
+ */
+function parseHeadersString(headersStr: string): Record<string, string> {
+  const headers: Record<string, string> = {};
+  if (!headersStr) return headers;
+
+  headersStr.split(",").forEach((pair) => {
+    const [name, ...valueParts] = pair.split("=");
+    if (name && valueParts.length > 0) {
+      headers[name.trim()] = valueParts.join("=").trim();
+    }
+  });
+
+  return headers;
+}
+
+export function getOTLPTracerProvider(): OTELTracerProvider {
+  if (!HAS_OTEL) {
+    throw new Error(
+      "OpenTelemetry packages are required to use this function. " +
+        "Please install the required OpenTelemetry packages."
+    );
+  }
+
+  // Set LangSmith-specific defaults if not already set in environment
+  if (!getEnvironmentVariable("OTEL_EXPORTER_OTLP_ENDPOINT")) {
+    const lsEndpoint =
+      getEnvironmentVariable("LANGSMITH_ENDPOINT") ||
+      getEnvironmentVariable("LANGCHAIN_ENDPOINT") ||
+      "https://api.smith.langchain.com";
+    setEnvironmentVariable("OTEL_EXPORTER_OTLP_ENDPOINT", `${lsEndpoint}/otel`);
+  }
+
+  // Configure headers with API key and project if available
+  if (!getEnvironmentVariable("OTEL_EXPORTER_OTLP_HEADERS")) {
+    const apiKey =
+      getEnvironmentVariable("LANGSMITH_API_KEY") ||
+      getEnvironmentVariable("LANGCHAIN_API_KEY");
+
+    if (!apiKey) {
+      throw new Error(
+        "LANGSMITH_API_KEY or LANGCHAIN_API_KEY environment variable is required"
+      );
+    }
+
+    let headers = `x-api-key=${apiKey}`;
+
+    const project =
+      getEnvironmentVariable("LANGSMITH_PROJECT") ||
+      getEnvironmentVariable("LANGCHAIN_PROJECT");
+    if (project) {
+      headers += `,Langsmith-Project=${project}`;
+    }
+
+    setEnvironmentVariable("OTEL_EXPORTER_OTLP_HEADERS", headers);
+  }
+
+  const headersStr = getEnvironmentVariable("OTEL_EXPORTER_OTLP_HEADERS") || "";
+  const headersObj = parseHeadersString(headersStr);
+
+  const langsmithSpanExporter = new OTLPTraceExporter({
+    url: getEnvironmentVariable("OTEL_EXPORTER_OTLP_ENDPOINT"),
+    headers: headersObj,
+  });
+  const spanProcessor = new BatchSpanProcessor(langsmithSpanExporter);
+
+  return new BasicTracerProvider({
+    spanProcessors: [spanProcessor],
+  });
+}

js/src/_internal/otel/index.ts

@@ -0,0 +1,3 @@
+export * from "./client.js";
+export * from "./translator.js";
+export * from "./utils.js";