java-topology/defects/pulsar/unit/Pulsar0007ModularLoadMgrTest.java

package unit;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * CWE-407 unit test: pulsar-0007
 *
 * Models ModularLoadManagerImpl.reapDeadBrokerPreallocations(List<String> aliveBrokers).
 *
 * DEFECT: The method takes List<String> aliveBrokers from listLocks().
 *         For each broker in loadData.getBrokerData().keySet(),
 *         it calls aliveBrokers.contains(broker) — O(B) per iteration.
 *         Total: O(B²) triggered on every broker metadata notification.
 *
 * FIX:    Convert aliveBrokers to HashSet<String> at method entry.
 *         contains() becomes O(1); total: O(B).
 *
 * Asserts: slowOps > fastOps * 10 at B=500 brokers.
 */
public class Pulsar0007ModularLoadMgrTest {

    /**
     * Simulates defective reapDeadBrokerPreallocations.
     * aliveBrokers is a List<String> — contains() is O(B).
     */
    static long slow(int numBrokers, int numDead) {
        // numBrokers total, numDead are dead (not in alive list)
        List<String> aliveBrokers = new ArrayList<>();
        Set<String> allBrokerSet = new HashSet<>();
        for (int i = numDead; i < numBrokers; i++) {
            String broker = "broker-" + i + ":8080";
            aliveBrokers.add(broker);
        }
        // All brokers in loadData (both alive and dead)
        List<String> allBrokers = new ArrayList<>();
        for (int i = 0; i < numBrokers; i++) {
            allBrokers.add("broker-" + i + ":8080");
        }

        long ops = 0;
        for (String broker : allBrokers) {
            // O(alive.size()) scan — the defect
            for (String alive : aliveBrokers) {
                ops++;
                if (alive.equals(broker)) break;
                // if not found, we scan the entire list
            }
            // In the real code, also checks contains() returning false for dead brokers
            // For dead brokers, the full list is scanned
        }
        return ops;
    }

    /**
     * Simulates the patched version.
     * Converts aliveBrokers List to HashSet at method entry.
     */
    static long fast(int numBrokers, int numDead) {
        List<String> aliveBrokersList = new ArrayList<>();
        for (int i = numDead; i < numBrokers; i++) {
            aliveBrokersList.add("broker-" + i + ":8080");
        }
        Set<String> aliveBrokersSet = new HashSet<>(aliveBrokersList); // O(B) once

        List<String> allBrokers = new ArrayList<>();
        for (int i = 0; i < numBrokers; i++) {
            allBrokers.add("broker-" + i + ":8080");
        }

        long ops = 0;
        for (String broker : allBrokers) {
            ops++; // O(1) hash probe
            aliveBrokersSet.contains(broker);
        }
        return ops;
    }

    /**
     * Count accurate dead-broker detections (correctness check).
     */
    static int countDead(List<String> all, List<String> alive) {
        int count = 0;
        for (String broker : all) {
            if (!alive.contains(broker)) count++;
        }
        return count;
    }

    static int countDeadFast(List<String> all, List<String> alive) {
        Set<String> aliveSet = new HashSet<>(alive);
        int count = 0;
        for (String broker : all) {
            if (!aliveSet.contains(broker)) count++;
        }
        return count;
    }

    public static void main(String[] args) {
        int passed = 0;
        int total = 0;

        // Test 1: 200 brokers, 20 dead
        {
            total++;
            int B = 200, D = 20;
            long sOps = slow(B, D);
            long fOps = fast(B, D);
            // slow: for each of B brokers, scans up to (B-D) alive brokers = ~36000
            // fast: B ops = 200
            boolean ok = sOps > fOps * 10L;
            System.out.printf("Test 1 [B=%d dead=%d slow=%d fast=%d ratio=%.1fx]: %s%n",
                    B, D, sOps, fOps, (double) sOps / fOps, ok ? "PASS" : "FAIL");
            if (ok) passed++;
        }

        // Test 2: 500 brokers, 50 dead
        {
            total++;
            int B = 500, D = 50;
            long sOps = slow(B, D);
            long fOps = fast(B, D);
            boolean ok = sOps > fOps * 50L;
            System.out.printf("Test 2 [B=%d dead=%d slow=%d fast=%d ratio=%.1fx]: %s%n",
                    B, D, sOps, fOps, (double) sOps / fOps, ok ? "PASS" : "FAIL");
            if (ok) passed++;
        }

        // Test 3: worst case — all brokers are dead (full scan per check)
        {
            total++;
            int B = 300;
            List<String> alive = new ArrayList<>(); // empty — all dead
            List<String> all = new ArrayList<>();
            for (int i = 0; i < B; i++) all.add("broker-" + i);

            long sOps = 0;
            for (String broker : all) {
                // contains on empty list — 0 ops but it returns immediately
                // Simulate non-empty alive list where none match
                for (String a : alive) { sOps++; if (a.equals(broker)) break; }
                sOps++; // simulate the contains() call cost even for empty
            }
            // Use a more interesting case: alive list has B/2 different brokers
            List<String> aliveHalf = new ArrayList<>();
            for (int i = B; i < B + B / 2; i++) aliveHalf.add("broker-" + i);
            List<String> allB = new ArrayList<>();
            for (int i = 0; i < B; i++) allB.add("broker-" + i);

            long slowOps = 0;
            for (String broker : allB) {
                for (String a : aliveHalf) { slowOps++; if (a.equals(broker)) break; }
            }
            long fastOps = 0;
            Set<String> aliveSet = new HashSet<>(aliveHalf);
            for (String broker : allB) { fastOps++; aliveSet.contains(broker); }

            boolean ok = slowOps > fastOps * 50L;
            System.out.printf("Test 3 [B=%d all-dead slow=%d fast=%d ratio=%.1fx]: %s%n",
                    B, slowOps, fastOps, (double) slowOps / fastOps, ok ? "PASS" : "FAIL");
            if (ok) passed++;
        }

        // Test 4: correctness — same dead broker detection
        {
            total++;
            int B = 100, D = 10;
            List<String> all = new ArrayList<>();
            List<String> alive = new ArrayList<>();
            for (int i = 0; i < B; i++) all.add("broker-" + i);
            for (int i = D; i < B; i++) alive.add("broker-" + i);

            int slowDead = countDead(all, alive);
            int fastDead = countDeadFast(all, alive);

            boolean ok = slowDead == D && fastDead == D && slowDead == fastDead;
            System.out.printf("Test 4 [correctness dead_expected=%d slow=%d fast=%d equal=%b]: %s%n",
                    D, slowDead, fastDead, slowDead == fastDead, ok ? "PASS" : "FAIL");
            if (ok) passed++;
        }

        System.out.printf("%d/%d PASS%n", passed, total);
        if (passed != total) System.exit(1);
    }
}