front_end/models/trace/lantern/simulation/ConnectionPool.test.ts

// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import * as Lantern from '../lantern.js';

const {ConnectionPool} = Lantern.Simulation;

describe('ConnectionPool', () => {
  const rtt = 100;
  const throughput = 10000 * 1024;
  let requestId: number;

  function request(data: Partial<Lantern.Types.NetworkRequest> = {}): Lantern.Types.NetworkRequest {
    const url = data.url || 'http://example.com';
    const origin = new URL(url).origin;
    const scheme = url.split(':')[0];
    const host = new URL(url).hostname;

    return {
      requestId: String(requestId++),
      url,
      protocol: 'http/1.1',
      parsedURL: {scheme, securityOrigin: origin, host},
      ...data,
    } as Lantern.Types.NetworkRequest;
  }

  function simulationOptions(options: {
    rtt?: number,
    throughput?: number,
    additionalRttByOrigin?: Map<string, number>,
    serverResponseTimeByOrigin?: Map<string, number>,
  }): Required<Lantern.Types.Simulation.Options> {
    const defaults: Required<Lantern.Types.Simulation.Options> = {
      rtt: 150,
      throughput: 1024,
      additionalRttByOrigin: new Map(),
      serverResponseTimeByOrigin: new Map(),
      // These options are not used by ConnectionPool, but are required in the types.
      cpuSlowdownMultiplier: 1,
      layoutTaskMultiplier: 1,
      observedThroughput: 1,
      maximumConcurrentRequests: 8,
    };
    return Object.assign(defaults, options);
  }

  beforeEach(() => {
    requestId = 1;
  });

  describe('#constructor', () => {
    it('should create the pool', () => {
      const pool = new ConnectionPool([request()], simulationOptions({rtt, throughput}));
      // Make sure 6 connections are created for each origin
      assert.lengthOf(pool.connectionsByOrigin.get('http://example.com') ?? [], 6);
      // Make sure it populates connectionWasReused
      assert.isFalse(pool.connectionReusedByRequestId.get('1'));

      const connection = pool.connectionsByOrigin.get('http://example.com')?.[0];
      assert.isOk(connection);
      assert.strictEqual(connection.rtt, rtt);
      assert.strictEqual(connection.throughput, throughput);
      assert.strictEqual(connection.serverLatency, 30);  // sets to default value
    });

    it('should set TLS properly', () => {
      const recordA = request({url: 'https://example.com'});
      const pool = new ConnectionPool([recordA], simulationOptions({rtt, throughput}));
      const connection = pool.connectionsByOrigin.get('https://example.com')?.[0];
      assert.isOk(connection?.ssl, 'should have set connection TLS');
    });

    it('should set H2 properly', () => {
      const recordA = request({protocol: 'h2'});
      const pool = new ConnectionPool([recordA], simulationOptions({rtt, throughput}));
      const connection = pool.connectionsByOrigin.get('http://example.com')?.[0];
      assert.isOk(connection?.isH2(), 'should have set HTTP/2');
      assert.lengthOf(pool.connectionsByOrigin.get('http://example.com') ?? [], 1);
    });

    it('should set origin-specific RTT properly', () => {
      const additionalRttByOrigin = new Map([['http://example.com', 63]]);
      const pool = new ConnectionPool([request()], simulationOptions({rtt, throughput, additionalRttByOrigin}));
      const connection = pool.connectionsByOrigin.get('http://example.com')?.[0];
      assert.isOk(connection);
      assert.strictEqual(connection.rtt, rtt + 63);
    });

    it('should set origin-specific server latency properly', () => {
      const serverResponseTimeByOrigin = new Map([['http://example.com', 63]]);
      const pool = new ConnectionPool([request()], simulationOptions({rtt, throughput, serverResponseTimeByOrigin}));
      const connection = pool.connectionsByOrigin.get('http://example.com')?.[0];
      assert.isOk(connection);
      assert.strictEqual(connection.serverLatency, 63);
    });
  });

  describe('.acquire', () => {
    it('should remember the connection associated with each request', () => {
      const requestA = request();
      const requestB = request();
      const pool = new ConnectionPool([requestA, requestB], simulationOptions({rtt, throughput}));

      const connectionForA = pool.acquire(requestA);
      const connectionForB = pool.acquire(requestB);
      for (let i = 0; i < 10; i++) {
        assert.strictEqual(pool.acquireActiveConnectionFromRequest(requestA), connectionForA);
        assert.strictEqual(pool.acquireActiveConnectionFromRequest(requestB), connectionForB);
      }

      assert.deepEqual(pool.connectionsInUse(), [connectionForA, connectionForB]);
    });

    it('should allocate at least 6 connections', () => {
      const pool = new ConnectionPool([request()], simulationOptions({rtt, throughput}));
      for (let i = 0; i < 6; i++) {
        assert.isOk(pool.acquire(request()), `did not find connection for ${i}th request`);
      }
    });

    it('should allocate all connections', () => {
      const records = new Array(7).fill(undefined, 0, 7).map(() => request());
      const pool = new ConnectionPool(records, simulationOptions({rtt, throughput}));
      const connections = records.map(request => pool.acquire(request));
      assert.isOk(connections[0], 'did not find connection for 1st request');
      assert.isOk(connections[5], 'did not find connection for 6th request');
      assert.isOk(connections[6], 'did not find connection for 7th request');
    });

    it('should be oblivious to connection reuse', () => {
      const coldRecord = request();
      const warmRecord = request();
      const pool = new ConnectionPool([coldRecord, warmRecord], simulationOptions({rtt, throughput}));
      pool.connectionReusedByRequestId.set(warmRecord.requestId, true);

      assert.isOk(pool.acquire(coldRecord), 'should have acquired connection');
      assert.isOk(pool.acquire(warmRecord), 'should have acquired connection');
      pool.release(coldRecord);

      for (const connection of pool.connectionsByOrigin.get('http://example.com') ?? []) {
        connection.setWarmed(true);
      }

      assert.isOk(pool.acquire(coldRecord), 'should have acquired connection');
      assert.isOk(pool.acquireActiveConnectionFromRequest(warmRecord), 'should have acquired connection');
    });

    it('should acquire in order of warmness', () => {
      const recordA = request();
      const recordB = request();
      const recordC = request();
      const pool = new ConnectionPool([recordA, recordB, recordC], simulationOptions({rtt, throughput}));
      pool.connectionReusedByRequestId.set(recordA.requestId, true);
      pool.connectionReusedByRequestId.set(recordB.requestId, true);
      pool.connectionReusedByRequestId.set(recordC.requestId, true);

      const connections = pool.connectionsByOrigin.get('http://example.com');
      assert.isOk(connections);
      const [connectionWarm, connectionWarmer, connectionWarmest] = connections;
      connectionWarm.setWarmed(true);
      connectionWarm.setCongestionWindow(10);
      connectionWarmer.setWarmed(true);
      connectionWarmer.setCongestionWindow(100);
      connectionWarmest.setWarmed(true);
      connectionWarmest.setCongestionWindow(1000);

      assert.strictEqual(pool.acquire(recordA), connectionWarmest);
      assert.strictEqual(pool.acquire(recordB), connectionWarmer);
      assert.strictEqual(pool.acquire(recordC), connectionWarm);
    });
  });

  describe('.release', () => {
    it('noop for request without connection', () => {
      const requestA = request();
      const pool = new ConnectionPool([requestA], simulationOptions({rtt, throughput}));
      assert.isUndefined(pool.release(requestA));
    });

    it('frees the connection for reissue', () => {
      const requests = new Array(6).fill(undefined, 0, 7).map(() => request());
      const pool = new ConnectionPool(requests, simulationOptions({rtt, throughput}));
      requests.push(request());

      requests.forEach(request => pool.acquire(request));

      assert.lengthOf(pool.connectionsInUse(), 6);
      assert.isNotOk(pool.acquire(requests[6]), 'had connection that is in use');

      pool.release(requests[0]);
      assert.lengthOf(pool.connectionsInUse(), 5);

      assert.isOk(pool.acquire(requests[6]), 'could not reissue released connection');
      assert.isNotOk(pool.acquire(requests[0]), 'had connection that is in use');
    });
  });
});