java-topology/defects/kylin/unit/JobSchedulerAlgorithm.java

package unit;

import java.util.*;
import java.util.stream.*;

/**
 * Standalone unit test for kylin-0001:
 * JdbcJobScheduler — List<String>.contains() in stream filter → O(J²).
 *
 * Simulates the releaseJobLock() pattern:
 *   jobInfoIds collected as List<String>, then used in stream filter with .contains().
 *
 * Compile: javac -d . JobSchedulerAlgorithm.java
 * Run:     java unit.JobSchedulerAlgorithm
 */
public class JobSchedulerAlgorithm {

    // ── Result ───────────────────────────────────────────────────────────────

    static class Result {
        final List<String> toRemoveLocks;
        final long ns;
        Result(List<String> locks, long ns) { this.toRemoveLocks = locks; this.ns = ns; }
    }

    // ── Defective: collects jobInfoIds into List → O(J) .contains per jobId ─

    static class DefectiveAlgorithm {
        /**
         * @param jobIds     all job IDs found in the lock table
         * @param jobInfoIds job IDs that have corresponding JobInfo records (as List)
         */
        Result releaseJobLock(List<String> jobIds, List<String> jobInfoIds) {
            long t0 = System.nanoTime();
            // Mirrors the defective code:
            //   List<String> jobInfoIds = jobs.stream().map(JobInfo::getJobId).collect(Collectors.toList());
            //   ... filter(jobId -> !jobInfoIds.contains(jobId)) ...
            List<String> toRemoveLocks = jobIds.stream()
                    .filter(jobId -> !jobInfoIds.contains(jobId))  // CWE-407 site: O(J) per call
                    .collect(Collectors.toList());
            return new Result(toRemoveLocks, System.nanoTime() - t0);
        }
    }

    // ── Fixed: uses Set<String> → O(1) .contains ────────────────────────────

    static class FixedAlgorithm {
        Result releaseJobLock(List<String> jobIds, List<String> jobInfoIdsList) {
            long t0 = System.nanoTime();
            // Fix: collect into HashSet for O(1) membership
            Set<String> jobInfoIds = new HashSet<>(jobInfoIdsList);
            List<String> toRemoveLocks = jobIds.stream()
                    .filter(jobId -> !jobInfoIds.contains(jobId))  // O(1)
                    .collect(Collectors.toList());
            return new Result(toRemoveLocks, System.nanoTime() - t0);
        }
    }

    // ── Helpers ──────────────────────────────────────────────────────────────

    static List<String> makeJobIds(int N) {
        List<String> ids = new ArrayList<>(N);
        for (int i = 0; i < N; i++) ids.add("job-" + i);
        return ids;
    }

    // ── Assertions ───────────────────────────────────────────────────────────

    static void assertEquals(Object expected, Object actual, String msg) {
        if (!expected.equals(actual))
            throw new AssertionError(msg + ": expected=" + expected + " actual=" + actual);
    }

    static void assertTrue(boolean cond, String msg) {
        if (!cond) throw new AssertionError(msg);
    }

    public static void main(String[] args) {
        System.out.println("=== kylin-0001: JobSchedulerAlgorithm ===");

        DefectiveAlgorithm defAlg = new DefectiveAlgorithm();
        FixedAlgorithm fixAlg = new FixedAlgorithm();

        // Correctness test 1: some jobs have info, some don't
        {
            List<String> jobIds = makeJobIds(20);
            // Only even-numbered jobs have a JobInfo record
            List<String> jobInfoIds = jobIds.stream()
                    .filter(id -> Integer.parseInt(id.replace("job-", "")) % 2 == 0)
                    .collect(Collectors.toList());

            Result dr = defAlg.releaseJobLock(new ArrayList<>(jobIds), new ArrayList<>(jobInfoIds));
            Result fr = fixAlg.releaseJobLock(new ArrayList<>(jobIds), new ArrayList<>(jobInfoIds));

            // Sort both for comparison (order may differ)
            List<String> dSorted = new ArrayList<>(dr.toRemoveLocks); Collections.sort(dSorted);
            List<String> fSorted = new ArrayList<>(fr.toRemoveLocks); Collections.sort(fSorted);

            assertEquals(dSorted, fSorted, "toRemoveLocks contents");
            // All odd-numbered jobs should be in toRemoveLocks
            assertTrue(dr.toRemoveLocks.size() == 10, "expected 10 orphan locks, got " + dr.toRemoveLocks.size());
            System.out.println("PASS  correctness (J=20, half missing)");
        }

        // Correctness test 2: all jobs have info records (no locks to remove)
        {
            List<String> jobIds = makeJobIds(10);
            Result dr = defAlg.releaseJobLock(new ArrayList<>(jobIds), new ArrayList<>(jobIds));
            Result fr = fixAlg.releaseJobLock(new ArrayList<>(jobIds), new ArrayList<>(jobIds));
            assertEquals(0, dr.toRemoveLocks.size(), "no orphan locks (defective)");
            assertEquals(0, fr.toRemoveLocks.size(), "no orphan locks (fixed)");
            System.out.println("PASS  correctness all-present (J=10)");
        }

        // Benchmark at J=2000
        {
            int J = 2000;
            List<String> jobIds = makeJobIds(J);
            // Half the jobs have info records
            List<String> jobInfoIds = jobIds.subList(0, J / 2);

            // warm up
            for (int i = 0; i < 5; i++) {
                defAlg.releaseJobLock(new ArrayList<>(jobIds), new ArrayList<>(jobInfoIds));
                fixAlg.releaseJobLock(new ArrayList<>(jobIds), new ArrayList<>(jobInfoIds));
            }

            long defNs = 0, fixNs = 0;
            int reps = 30;
            for (int i = 0; i < reps; i++) {
                defNs += defAlg.releaseJobLock(new ArrayList<>(jobIds), new ArrayList<>(jobInfoIds)).ns;
                fixNs += fixAlg.releaseJobLock(new ArrayList<>(jobIds), new ArrayList<>(jobInfoIds)).ns;
            }
            defNs /= reps; fixNs /= reps;
            double ratio = (double) defNs / Math.max(1, fixNs);

            System.out.printf("BENCH J=%d reps=%d%n", J, reps);
            System.out.printf("  defective avg: %,d ns%n", defNs);
            System.out.printf("  fixed     avg: %,d ns%n", fixNs);
            System.out.printf("  speedup:       %.1fx%n", ratio);

            assertTrue(ratio >= 2.0, "Expected fixed >= 2x faster, got " + ratio + "x");
            System.out.println("PASS  speedup >= 2x");
        }

        System.out.println("=== ALL PASS ===");
    }
}