refactor(telemetry): OTel-format ids and explicit session id

The local JSONL output exposed two schema rough edges. First, session_id
was vscode.env.sessionId verbatim, which is a UUID concatenated with a
ms timestamp ("0f465473-...-bed92cb4ed3a1777982179036"), looking like a
malformed UUID. Second, event_id and trace_id were UUIDv4 with hyphens,
not the lowercase-hex form OTel uses, so a future exporter would need a
translation layer for no real reason.

- Add src/telemetry/ids.ts with newTraceId (16 bytes / 32 hex),
  newSpanId (8 bytes / 16 hex), and newSessionId (16 bytes / 32 hex).
  Names and widths match OTel.
- buildSession takes sessionId as a parameter instead of reading
  vscode.env.sessionId, decoupling our schema from VS Code's quirks.
- TelemetryService accepts sessionId in its constructor and forwards
  it to buildSession.
- ServiceContainer generates one sessionId via newSessionId() and
  threads it to both LocalJsonlSink (filename slug) and TelemetryService
  (event payload), so the on-disk filename and the session_id field
  always match.
- service.ts: replace crypto.randomUUID() with newSpanId / newTraceId
  at every event emission.
- Tests updated for the new sessionId parameter and the new id format
  regex (/^[0-9a-f]{16}$/ for event_id, sessionId is now an explicit
  test fixture).

trace_id stays on every event (including single-event "traces"). You
cannot know at emit time whether a phase child will follow, and a
consistent schema is more valuable to consumers than 36 bytes per
event.

Author: EhabY

src/core/container.ts

@@ -3,6 +3,7 @@ import * as vscode from "vscode";
 import { CoderApi } from "../api/coderApi";
 import { LoginCoordinator } from "../login/loginCoordinator";
 import { OAuthCallback } from "../oauth/oauthCallback";
+import { newSessionId } from "../telemetry/ids";
 import { TelemetryService } from "../telemetry/service";
 import { LocalJsonlSink } from "../telemetry/sinks/localJsonlSink";
 import { SpeedtestPanelFactory } from "../webviews/speedtest/speedtestPanelFactory";
@@ -93,15 +94,18 @@ export class ServiceContainer implements vscode.Disposable {
 			context.extensionUri,
 			this.logger,
 		);
+		// Shared by the sink (filename) and the service (event payload).
+		const sessionId = newSessionId();
 		const localJsonlSink = LocalJsonlSink.start(
 			{
 				baseDir: this.pathResolver.getTelemetryPath(),
-				sessionId: vscode.env.sessionId,
+				sessionId,
 			},
 			this.logger,
 		);
 		this.telemetryService = new TelemetryService(
 			context,
+			sessionId,
 			[localJsonlSink],
 			this.logger,
 		);

src/telemetry/event.ts

@@ -68,8 +68,12 @@ export interface TelemetrySink {
 	dispose(): Promise<void>;
 }
 
-/** Build session attributes. `extensionVersion` falls back to `"unknown"`. */
-export function buildSession(ctx: vscode.ExtensionContext): SessionContext {
+/** Build session attributes. `extensionVersion` falls back to `"unknown"`.
+ * `sessionId` is caller-supplied so payload and sink filename agree. */
+export function buildSession(
+	ctx: vscode.ExtensionContext,
+	sessionId: string,
+): SessionContext {
 	// "unknown" only for malformed package.json or test fixtures missing `version`.
 	const packageJson = ctx.extension.packageJSON as { version?: unknown };
 	const extensionVersion =
@@ -78,7 +82,7 @@ export function buildSession(ctx: vscode.ExtensionContext): SessionContext {
 	return {
 		extensionVersion,
 		machineId: vscode.env.machineId,
-		sessionId: vscode.env.sessionId,
+		sessionId,
 		osType: detectOsType(),
 		osVersion: os.release(),
 		hostArch: process.arch,

src/telemetry/ids.ts

@@ -0,0 +1,20 @@
+import { randomBytes } from "node:crypto";
+
+// OTel-format ids: lowercase hex, no separators. Keeps a future OTel
+// exporter a 1:1 mapping.
+
+/** OTel `trace_id`: 16 bytes / 32 hex. */
+export function newTraceId(): string {
+	return randomBytes(16).toString("hex");
+}
+
+/** OTel `span_id` (used as `event_id`): 8 bytes / 16 hex. */
+export function newSpanId(): string {
+	return randomBytes(8).toString("hex");
+}
+
+/** Our own session id (16 bytes / 32 hex). Avoids `vscode.env.sessionId`,
+ * which is a UUID concatenated with a timestamp. */
+export function newSessionId(): string {
+	return randomBytes(16).toString("hex");
+}

src/telemetry/service.ts

@@ -17,6 +17,7 @@ import {
 	type TelemetryLevel,
 	type TelemetrySink,
 } from "./event";
+import { newSpanId, newTraceId } from "./ids";
 import { NOOP_SPAN, type Span } from "./span";
 
 const LEVEL_ORDER: Readonly<Record<TelemetryLevel, number>> = {
@@ -53,10 +54,11 @@ export class TelemetryService implements vscode.Disposable {
 
 	public constructor(
 		ctx: vscode.ExtensionContext,
+		sessionId: string,
 		private readonly sinks: readonly TelemetrySink[],
 		private readonly logger: Logger,
 	) {
-		this.#session = buildSession(ctx);
+		this.#session = buildSession(ctx, sessionId);
 		this.#level = readLevel();
 		this.#configWatcher = watchConfigurationChanges(
 			[{ setting: TELEMETRY_LEVEL_SETTING, getValue: readLevel }],
@@ -86,7 +88,7 @@ export class TelemetryService implements vscode.Disposable {
 		if (this.#level === "off") {
 			return;
 		}
-		this.#safeEmit(crypto.randomUUID(), eventName, properties, measurements);
+		this.#safeEmit(newSpanId(), eventName, properties, measurements);
 	}
 
 	public logError(
@@ -98,7 +100,7 @@ export class TelemetryService implements vscode.Disposable {
 		if (this.#level === "off") {
 			return;
 		}
-		this.#safeEmit(crypto.randomUUID(), eventName, properties, measurements, {
+		this.#safeEmit(newSpanId(), eventName, properties, measurements, {
 			error,
 		});
 	}
@@ -118,7 +120,7 @@ export class TelemetryService implements vscode.Disposable {
 			return fn(NOOP_SPAN);
 		}
 		return this.#startSpan(eventName, fn, properties, measurements, {
-			traceId: crypto.randomUUID(),
+			traceId: newTraceId(),
 			traceLevel: this.#level,
 		});
 	}
@@ -140,7 +142,7 @@ export class TelemetryService implements vscode.Disposable {
 		measurements: Record<string, number>,
 		spanOpts: SpanOptions,
 	): Promise<T> {
-		const eventId = crypto.randomUUID();
+		const eventId = newSpanId();
 		const { traceId, traceLevel } = spanOpts;
 		const span: Span = {
 			traceId,

test/unit/core/commandManager.test.ts

@@ -35,6 +35,7 @@ function makeHarness(): Harness {
 	const sink = new TestSink();
 	const telemetry = new TelemetryService(
 		fakeContext(),
+		"test-session",
 		[sink],
 		createMockLogger(),
 	);

test/unit/telemetry/event.test.ts

@@ -12,12 +12,12 @@ function fakeContext(version: unknown = "1.2.3-test"): vscode.ExtensionContext {
 
 describe("buildSession", () => {
 	it("populates session-stable fields from the extension context, vscode env, and host", () => {
-		const session = buildSession(fakeContext());
+		const session = buildSession(fakeContext(), "session-abc");
 
 		expect(session).toMatchObject({
 			extensionVersion: "1.2.3-test",
 			machineId: "test-machine-id",
-			sessionId: "test-session-id",
+			sessionId: "session-abc",
 			platformName: "Visual Studio Code",
 			platformVersion: "1.106.0-test",
 			hostArch: process.arch,
@@ -32,8 +32,10 @@ describe("buildSession", () => {
 		const noVersion = {
 			extension: { packageJSON: {} },
 		} as unknown as vscode.ExtensionContext;
-		expect(buildSession(noVersion).extensionVersion).toBe("unknown");
-		expect(buildSession(fakeContext(123)).extensionVersion).toBe("unknown");
+		expect(buildSession(noVersion, "s").extensionVersion).toBe("unknown");
+		expect(buildSession(fakeContext(123), "s").extensionVersion).toBe(
+			"unknown",
+		);
 	});
 });
 

test/unit/telemetry/service.test.ts

@@ -24,12 +24,15 @@ interface Harness {
 	config: MockConfigurationProvider;
 }
 
+const TEST_SESSION_ID = "test-session";
+
 function makeHarness(level: "off" | "local" = "local"): Harness {
 	const config = new MockConfigurationProvider();
 	config.set("coder.telemetry.level", level);
 	const sink = new TestSink();
 	const service = new TelemetryService(
 		fakeContext(),
+		TEST_SESSION_ID,
 		[sink],
 		createMockLogger(),
 	);
@@ -38,7 +41,12 @@ function makeHarness(level: "off" | "local" = "local"): Harness {
 
 function makeService(sinks: TelemetrySink[]): TelemetryService {
 	new MockConfigurationProvider().set("coder.telemetry.level", "local");
-	return new TelemetryService(fakeContext(), sinks, createMockLogger());
+	return new TelemetryService(
+		fakeContext(),
+		TEST_SESSION_ID,
+		sinks,
+		createMockLogger(),
+	);
 }
 
 describe("TelemetryService", () => {
@@ -63,13 +71,11 @@ describe("TelemetryService", () => {
 				context: {
 					extensionVersion: "1.2.3-test",
 					machineId: "test-machine-id",
-					sessionId: "test-session-id",
+					sessionId: TEST_SESSION_ID,
 					deploymentUrl: "",
 				},
 			});
-			expect(event.eventId).toMatch(
-				/^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/,
-			);
+			expect(event.eventId).toMatch(/^[0-9a-f]{16}$/);
 			expect(event.timestamp).toMatch(/^\d{4}-\d{2}-\d{2}T/);
 		});