Manual protobuf encoding for OTLP (#81)

* Manual protobuf encoding for OTLP

* fix lints

* changeset

.changeset/brown-starfishes-drive.md

@@ -0,0 +1,5 @@
+---
+"@vercel/otel": patch
+---
+
+Manual protobuf encoding for OTLP to save about 180K binary size

.github/workflows/unit-test.yml

@@ -0,0 +1,36 @@
+name: Unit Tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    name: "unit tests"
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [18.x]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v2
+
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v3
+        with:
+          node-version: ${{ matrix.node-version }}
+          cache: "pnpm"
+
+      - name: Install dependencies
+        run: pnpm install
+
+      - name: Build
+        run: pnpm build
+
+      - name: Run unit  tests
+        run: pnpm unit-test

package.json

@@ -11,6 +11,7 @@
     "eslint-fix": "turbo eslint -- --fix",
     "release": "pnpm build && changeset publish",
     "type-check": "turbo --continue type-check",
+    "unit-test": "turbo unit-test",
     "version-packages": "changeset version && pnpm i --no-frozen-lockfile && git add ."
   },
   "keywords": [],

packages/otel/build.ts

@@ -1,9 +1,15 @@
+import { stat } from "node:fs/promises";
 import type { Plugin } from "esbuild";
 import { build } from "esbuild";
 
 const MINIFY = true;
 const SOURCEMAP = false;
 
+const MAX_SIZES = {
+  "dist/node/index.js": 210_000,
+  "dist/edge/index.js": 180_000,
+};
+
 type ExternalPluginFactory = (external: string[]) => Plugin;
 const externalCjsToEsmPlugin: ExternalPluginFactory = (external) => ({
   name: "external",
@@ -93,6 +99,25 @@ async function buildAll(): Promise<void> {
       ],
     }),
   ]);
+
+  // Check max size.
+  const errors: string[] = [];
+  for (const [file, maxSize] of Object.entries(MAX_SIZES)) {
+    // eslint-disable-next-line no-await-in-loop
+    const s = await stat(file);
+    if (s.size > maxSize) {
+      errors.push(
+        `${file}: the size of ${s.size} is over the maximum allowed size of ${maxSize}`
+      );
+    }
+  }
+  if (errors.length > 0) {
+    for (const error of errors) {
+      // eslint-disable-next-line no-console
+      console.error(error);
+    }
+    process.exit(1);
+  }
 }
 
 void buildAll();

packages/otel/package.json

@@ -50,6 +50,7 @@
   },
   "scripts": {
     "build": "pnpm clean && pnpm tsx build.ts && pnpm build-types && pnpm build-site",
+    "build-only": "pnpm tsx build.ts",
     "build-types": "tsc --noEmit false --declaration --emitDeclarationOnly --stripInternal --declarationDir dist/types src/index.ts",
     "build-site": "pnpm build-typedoc && cp index.html LICENSE CHANGELOG.md dist-site",
     "build-typedoc": "pnpm typedoc src/index.ts",
@@ -71,15 +72,16 @@
     "@opentelemetry/instrumentation": "^0.46.0",
     "@opentelemetry/otlp-exporter-base": "^0.46.0",
     "@opentelemetry/otlp-proto-exporter-base": "^0.46.0",
+    "@opentelemetry/otlp-transformer": "^0.46.0",
     "@opentelemetry/resources": "^1.19.0",
     "@opentelemetry/sdk-logs": "^0.46.0",
     "@opentelemetry/sdk-metrics": "^1.19.0",
-    "@opentelemetry/semantic-conventions": "^1.19.0",
-    "@opentelemetry/otlp-transformer": "^0.46.0",
     "@opentelemetry/sdk-trace-base": "^1.19.0",
+    "@opentelemetry/semantic-conventions": "^1.19.0",
     "@types/node": "18.15.11",
     "esbuild": "^0.19.4",
     "eslint-config": "workspace:*",
+    "protobufjs": "^7.2.6",
     "rimraf": "3.0.2",
     "tsx": "^4.6.2",
     "typedoc": "^0.25.8",

packages/otel/src/exporters/exporter-trace-otlp-proto-fetch.ts

@@ -1,12 +1,11 @@
 import type { ReadableSpan, SpanExporter } from "@opentelemetry/sdk-trace-base";
 import type { IExportTraceServiceRequest } from "@opentelemetry/otlp-transformer";
 import { createExportTraceServiceRequest } from "@opentelemetry/otlp-transformer/build/src/trace";
-import { ServiceClientType } from "@opentelemetry/otlp-proto-exporter-base/build/src/platform/index";
-import { getExportRequestProto } from "@opentelemetry/otlp-proto-exporter-base/build/src/platform/util";
 import type { ExportResult } from "@opentelemetry/core";
 import { OTLPExporterEdgeBase } from "./otlp-exporter-base";
 import { getDefaultUrl } from "./trace-config";
 import type { OTLPExporterConfig } from "./config";
+import { encodeTraceServiceRequest } from "./proto";
 
 /**
  * OTLP exporter for the `http/protobuf` protocol. Compatible with the "edge" runtime.
@@ -52,10 +51,7 @@ class Impl extends OTLPExporterEdgeBase<
     contentType: string;
     headers?: Record<string, string> | undefined;
   } {
-    const serviceClientType = ServiceClientType.SPANS;
-    const exportRequestType = getExportRequestProto(serviceClientType);
-    const message = exportRequestType.create(serviceRequest);
-    const body = exportRequestType.encode(message).finish();
+    const body = encodeTraceServiceRequest(serviceRequest);
     return {
       body,
       contentType: "application/x-protobuf",