Allow gzip compression in exporter

Author: Grzegorz Daszuta

README.md

@@ -12,6 +12,13 @@ npm install @microlabs/otel-cf-workers @opentelemetry/api
 > To be able to use the Open Telemetry library you have to add the NodeJS compatibility flag in your `wrangler.toml` file.
 
 ```
+compatibility_flags = [ "nodejs_compat", "nodejs_zlib" ]
+```
+
+alternatively, in recent version nodejs_zlib is enabled by default by nodejs_compat
+
+```
+compatibility_date = "2024-09-23"
 compatibility_flags = [ "nodejs_compat" ]
 ```
 
@@ -44,6 +51,7 @@ const config: ResolveConfigFn = (env: Env, _trigger) => {
 		exporter: {
 			url: 'https://api.honeycomb.io/v1/traces',
 			headers: { 'x-honeycomb-team': env.HONEYCOMB_API_KEY },
+			compression: 'gzip',
 		},
 		service: { name: 'greetings' },
 	}
@@ -263,6 +271,7 @@ One of the advantages of using Open Telemetry is that it makes it easier to do d
 
 - The worker runtime does not expose accurate timing information to protect against side-channel attacks such as Spectre and will only update the clock on IO, so any CPU heavy processing will look like it takes 0 milliseconds.
 - Not everything is auto-instrumented yet. See the lists below for what is and isn't.
+- Exporter protocol support is currently limited to http/json.
 
 Triggers:
 

examples/queue/wrangler.toml

@@ -1,7 +1,7 @@
 name = "queues-example"
 main = "src/index.ts"
 compatibility_date = "2023-04-02"
-compatibility_flags = [ "nodejs_compat" ]
+compatibility_flags = [ "nodejs_compat", "nodejs_zlib ]
 
 # Worker defines a binding, named "QUEUE", which gives it a capability
 # to send messages to a Queue, named "my-queue".

examples/quickstart/QUICKSTART_GUIDE.md

@@ -12,7 +12,7 @@ npm install @microlabs/otel-cf-workers @opentelemetry/api
 npx wrangler secret put HONEYCOMB_API_KEY
 ```
 
-And set the Node Compatibility flag by adding `compatibility_flags = [ "nodejs_compat" ]`
+And set the Node Compatibility flag by adding `compatibility_flags = [ "nodejs_compat", "nodejs_zlib ]`
 in your `wrangler.toml`
 
 ## Example
@@ -52,6 +52,7 @@ const config: ResolveConfigFn = (env: Env, _trigger: any) => {
 		exporter: {
 			url: 'https://api.honeycomb.io/v1/traces',
 			headers: { 'x-honeycomb-team': env.HONEYCOMB_API_KEY },
+			compression: 'gzip',
 		},
 		service: { name: 'my-service-name' },
 	}

examples/quickstart/wrangler.toml

@@ -2,7 +2,7 @@
 name = "otel-quickstart-example"
 main = "src/index.ts"
 compatibility_date = "2024-09-09"
-compatibility_flags = [ "nodejs_compat" ]
+compatibility_flags = [ "nodejs_compat", "nodejs_zlib ]
 
 # [vars]
 HONEYCOMB_API_KEY = "example"

examples/worker/wrangler.toml

@@ -1,7 +1,7 @@
 name = "otel-test"
 main = "src/index.ts"
 compatibility_date = "2023-03-27"
-compatibility_flags = [ "nodejs_compat" ]
+compatibility_flags = [ "nodejs_compat", "nodejs_zlib ]
 
 kv_namespaces = [
   { binding = "OTEL_TEST", id = "f124c9696873443da0a277ddb75000ca", preview_id = "3569aab8617645d9b8ed4bd1d45c8d96" }

src/exporter.ts

@@ -1,12 +1,14 @@
-import { createExportTraceServiceRequest } from '@opentelemetry/otlp-transformer'
+import { createExportTraceServiceRequest, IExportTraceServiceRequest } from '@opentelemetry/otlp-transformer'
 import { ExportServiceError, OTLPExporterError } from '@opentelemetry/otlp-exporter-base'
 import { ExportResult, ExportResultCode } from '@opentelemetry/core'
 import { SpanExporter } from '@opentelemetry/sdk-trace-base'
 import { unwrap } from './wrap.js'
+import { gzip } from 'node:zlib'
 
 export interface OTLPExporterConfig {
 	url: string
 	headers?: Record<string, string>
+	compression?: 'gzip'
 }
 
 const defaultHeaders: Record<string, string> = {
@@ -17,9 +19,11 @@ const defaultHeaders: Record<string, string> = {
 export class OTLPExporter implements SpanExporter {
 	private headers: Record<string, string>
 	private url: string
+	private compression?: string
 	constructor(config: OTLPExporterConfig) {
 		this.url = config.url
 		this.headers = Object.assign({}, defaultHeaders, config.headers)
+		this.compression = config.compression
 	}
 
 	export(items: any[], resultCallback: (result: ExportResult) => void): void {
@@ -42,19 +46,61 @@ export class OTLPExporter implements SpanExporter {
 		})
 	}
 
-	send(items: any[], onSuccess: () => void, onError: (error: OTLPExporterError) => void): void {
+	private async gzipCompress(input: string, options = {}): Promise<Buffer> {
+		const output = (await new Promise((resolve, reject) => {
+			gzip(input, options, function (error, result) {
+				if (error) {
+					reject(error)
+				} else {
+					resolve(result)
+				}
+			})
+		})) as Buffer
+
+		return output
+	}
+
+	private async getBody(exportMessage: IExportTraceServiceRequest): Promise<string | Buffer> {
+		const jsonMessage = JSON.stringify(exportMessage)
+
+		if (this.compression === 'gzip') {
+			return await this.gzipCompress(jsonMessage)
+		}
+
+		return jsonMessage
+	}
+
+	private getHeaders(): HeadersInit {
+		const headers = { ...this.headers }
+
+		if (this.compression === 'gzip') {
+			headers['content-encoding'] = 'gzip'
+		}
+
+		return headers
+	}
+
+	private async prepareRequest(items: any[]): Promise<RequestInit> {
 		const exportMessage = createExportTraceServiceRequest(items, {
 			useHex: true,
 			useLongBits: false,
 		})
-		const body = JSON.stringify(exportMessage)
+
+		const body = await this.getBody(exportMessage)
+		const headers = this.getHeaders()
+
 		const params: RequestInit = {
 			method: 'POST',
-			headers: this.headers,
+			headers,
 			body,
 		}
 
-		unwrap(fetch)(this.url, params)
+		return params
+	}
+
+	send(items: any[], onSuccess: () => void, onError: (error: OTLPExporterError) => void): void {
+		this.prepareRequest(items)
+			.then((params) => unwrap(fetch)(this.url, params))
 			.then((response) => {
 				if (response.ok) {
 					onSuccess()