ProfilingPlugin.js

const fs = require("fs");
const { Tracer } = require("chrome-trace-event");
const validateOptions = require("schema-utils");
const schema = require("../../schemas/plugins/debug/ProfilingPlugin.json");
let inspector = undefined;

try {
	// eslint-disable-next-line node/no-unsupported-features/node-builtins
	inspector = require("inspector");
} catch (e) {
	console.log("Unable to CPU profile in < node 8.0");
}

class Profiler {
	constructor(inspector) {
		this.session = undefined;
		this.inspector = inspector;
	}

	hasSession() {
		return this.session !== undefined;
	}

	startProfiling() {
		if (this.inspector === undefined) {
			return Promise.resolve();
		}

		try {
			this.session = new inspector.Session();
			this.session.connect();
		} catch (_) {
			this.session = undefined;
			return Promise.resolve();
		}

		return Promise.all([
			this.sendCommand("Profiler.setSamplingInterval", {
				interval: 100
			}),
			this.sendCommand("Profiler.enable"),
			this.sendCommand("Profiler.start")
		]);
	}

	sendCommand(method, params) {
		if (this.hasSession()) {
			return new Promise((res, rej) => {
				return this.session.post(method, params, (err, params) => {
					if (err !== null) {
						rej(err);
					} else {
						res(params);
					}
				});
			});
		} else {
			return Promise.resolve();
		}
	}

	destroy() {
		if (this.hasSession()) {
			this.session.disconnect();
		}

		return Promise.resolve();
	}

	stopProfiling() {
		return this.sendCommand("Profiler.stop");
	}
}

/**
 * @typedef {Object} Trace
 * @description an object that wraps Tracer and Profiler with a counter
 * @property {Tracer} trace instance of Tracer
 * @property {number} counter Counter
 * @property {Profiler} profiler instance of Profiler
 * @property {Function} end the end function
 */

/**
 * @param {string} outputPath The location where to write the log.
 * @returns {Trace} The trace object
 */
const createTrace = outputPath => {
	const trace = new Tracer({
		noStream: true
	});
	const profiler = new Profiler(inspector);
	const fsStream = fs.createWriteStream(outputPath);

	let counter = 0;

	trace.pipe(fsStream);
	// These are critical events that need to be inserted so that tools like
	// chrome dev tools can load the profile.
	trace.instantEvent({
		name: "TracingStartedInPage",
		id: ++counter,
		cat: ["disabled-by-default-devtools.timeline"],
		args: {
			data: {
				sessionId: "-1",
				page: "0xfff",
				frames: [
					{
						frame: "0xfff",
						url: "webpack",
						name: ""
					}
				]
			}
		}
	});

	trace.instantEvent({
		name: "TracingStartedInBrowser",
		id: ++counter,
		cat: ["disabled-by-default-devtools.timeline"],
		args: {
			data: {
				sessionId: "-1"
			}
		}
	});

	return {
		trace,
		counter,
		profiler,
		end: callback => {
			// Wait until the write stream finishes.
			fsStream.on("finish", () => {
				callback();
			});
			// Tear down the readable trace stream.
			trace.push(null);
		}
	};
};

const pluginName = "ProfilingPlugin";

class ProfilingPlugin {
	constructor(opts) {
		validateOptions(schema, opts || {}, "Profiling plugin");
		opts = opts || {};
		this.outputPath = opts.outputPath || "events.json";
	}

	apply(compiler) {
		const tracer = createTrace(this.outputPath);
		tracer.profiler.startProfiling();

		// Compiler Hooks
		Object.keys(compiler.hooks).forEach(hookName => {
			compiler.hooks[hookName].intercept(
				makeInterceptorFor("Compiler", tracer)(hookName)
			);
		});

		Object.keys(compiler.resolverFactory.hooks).forEach(hookName => {
			compiler.resolverFactory.hooks[hookName].intercept(
				makeInterceptorFor("Resolver", tracer)(hookName)
			);
		});

		compiler.hooks.compilation.tap(
			pluginName,
			(compilation, { normalModuleFactory, contextModuleFactory }) => {
				interceptAllHooksFor(compilation, tracer, "Compilation");
				interceptAllHooksFor(
					normalModuleFactory,
					tracer,
					"Normal Module Factory"
				);
				interceptAllHooksFor(
					contextModuleFactory,
					tracer,
					"Context Module Factory"
				);
				interceptAllParserHooks(normalModuleFactory, tracer);
				interceptTemplateInstancesFrom(compilation, tracer);
			}
		);

		// We need to write out the CPU profile when we are all done.
		compiler.hooks.done.tapAsync(
			{
				name: pluginName,
				stage: Infinity
			},
			(stats, callback) => {
				tracer.profiler.stopProfiling().then(parsedResults => {
					if (parsedResults === undefined) {
						tracer.profiler.destroy();
						tracer.trace.flush();
						tracer.end(callback);
						return;
					}

					const cpuStartTime = parsedResults.profile.startTime;
					const cpuEndTime = parsedResults.profile.endTime;

					tracer.trace.completeEvent({
						name: "TaskQueueManager::ProcessTaskFromWorkQueue",
						id: ++tracer.counter,
						cat: ["toplevel"],
						ts: cpuStartTime,
						args: {
							src_file: "../../ipc/ipc_moji_bootstrap.cc",
							src_func: "Accept"
						}
					});

					tracer.trace.completeEvent({
						name: "EvaluateScript",
						id: ++tracer.counter,
						cat: ["devtools.timeline"],
						ts: cpuStartTime,
						dur: cpuEndTime - cpuStartTime,
						args: {
							data: {
								url: "webpack",
								lineNumber: 1,
								columnNumber: 1,
								frame: "0xFFF"
							}
						}
					});

					tracer.trace.instantEvent({
						name: "CpuProfile",
						id: ++tracer.counter,
						cat: ["disabled-by-default-devtools.timeline"],
						ts: cpuEndTime,
						args: {
							data: {
								cpuProfile: parsedResults.profile
							}
						}
					});

					tracer.profiler.destroy();
					tracer.trace.flush();
					tracer.end(callback);
				});
			}
		);
	}
}

const interceptTemplateInstancesFrom = (compilation, tracer) => {
	const {
		mainTemplate,
		chunkTemplate,
		hotUpdateChunkTemplate,
		moduleTemplates
	} = compilation;

	const { javascript, webassembly } = moduleTemplates;

	[
		{
			instance: mainTemplate,
			name: "MainTemplate"
		},
		{
			instance: chunkTemplate,
			name: "ChunkTemplate"
		},
		{
			instance: hotUpdateChunkTemplate,
			name: "HotUpdateChunkTemplate"
		},
		{
			instance: javascript,
			name: "JavaScriptModuleTemplate"
		},
		{
			instance: webassembly,
			name: "WebAssemblyModuleTemplate"
		}
	].forEach(templateObject => {
		Object.keys(templateObject.instance.hooks).forEach(hookName => {
			templateObject.instance.hooks[hookName].intercept(
				makeInterceptorFor(templateObject.name, tracer)(hookName)
			);
		});
	});
};

const interceptAllHooksFor = (instance, tracer, logLabel) => {
	if (Reflect.has(instance, "hooks")) {
		Object.keys(instance.hooks).forEach(hookName => {
			instance.hooks[hookName].intercept(
				makeInterceptorFor(logLabel, tracer)(hookName)
			);
		});
	}
};

const interceptAllParserHooks = (moduleFactory, tracer) => {
	const moduleTypes = [
		"javascript/auto",
		"javascript/dynamic",
		"javascript/esm",
		"json",
		"webassembly/experimental"
	];

	moduleTypes.forEach(moduleType => {
		moduleFactory.hooks.parser
			.for(moduleType)
			.tap("ProfilingPlugin", (parser, parserOpts) => {
				interceptAllHooksFor(parser, tracer, "Parser");
			});
	});
};

const makeInterceptorFor = (instance, tracer) => hookName => ({
	register: ({ name, type, context, fn }) => {
		const newFn = makeNewProfiledTapFn(hookName, tracer, {
			name,
			type,
			fn
		});
		return {
			name,
			type,
			context,
			fn: newFn
		};
	}
});

// TODO improve typing
/** @typedef {(...args: TODO[]) => void | Promise<TODO>} PluginFunction */

/**
 * @param {string} hookName Name of the hook to profile.
 * @param {Trace} tracer The trace object.
 * @param {object} options Options for the profiled fn.
 * @param {string} options.name Plugin name
 * @param {string} options.type Plugin type (sync | async | promise)
 * @param {PluginFunction} options.fn Plugin function
 * @returns {PluginFunction} Chainable hooked function.
 */
const makeNewProfiledTapFn = (hookName, tracer, { name, type, fn }) => {
	const defaultCategory = ["blink.user_timing"];

	switch (type) {
		case "promise":
			return (...args) => {
				const id = ++tracer.counter;
				tracer.trace.begin({
					name,
					id,
					cat: defaultCategory
				});
				const promise = /** @type {Promise<*>} */ (fn(...args));
				return promise.then(r => {
					tracer.trace.end({
						name,
						id,
						cat: defaultCategory
					});
					return r;
				});
			};
		case "async":
			return (...args) => {
				const id = ++tracer.counter;
				tracer.trace.begin({
					name,
					id,
					cat: defaultCategory
				});
				fn(...args, (...r) => {
					const callback = args.pop();
					tracer.trace.end({
						name,
						id,
						cat: defaultCategory
					});
					callback(...r);
				});
			};
		case "sync":
			return (...args) => {
				const id = ++tracer.counter;
				// Do not instrument ourself due to the CPU
				// profile needing to be the last event in the trace.
				if (name === pluginName) {
					return fn(...args);
				}

				tracer.trace.begin({
					name,
					id,
					cat: defaultCategory
				});
				let r;
				try {
					r = fn(...args);
				} catch (error) {
					tracer.trace.end({
						name,
						id,
						cat: defaultCategory
					});
					throw error;
				}
				tracer.trace.end({
					name,
					id,
					cat: defaultCategory
				});
				return r;
			};
		default:
			break;
	}
};

module.exports = ProfilingPlugin;
module.exports.Profiler = Profiler;