java-topology/defects/haproxy/unit/HaproxyPatMatchBinAlgorithmTest.java

package unit;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * haproxy-0001: pat_match_bin list walk below LRU threshold vs O(1) map lookup.
 *
 * slow() models the defect: linked-list walk (no LRU cache, <20 entries) per request.
 * fast() models the fix: HashMap lookup at O(1) regardless of pattern count.
 *
 * Assert: slowOps > fastOps * 5 for P=15 patterns (below LRU threshold).
 */
public class HaproxyPatMatchBinAlgorithmTest {

    static long slowOps;
    static long fastOps;

    // ---- simulated pattern entry -------------------------------------------

    static class BinPattern {
        final byte[] data;
        BinPattern(byte[] data) { this.data = data; }
    }

    // ---- slow: O(P) list walk (defect) -------------------------------------

    static boolean slowMatchBin(List<BinPattern> patterns, byte[] sample) {
        for (BinPattern p : patterns) {
            slowOps++;
            if (p.data.length == sample.length) {
                boolean eq = true;
                for (int i = 0; i < sample.length; i++) {
                    if (p.data[i] != sample[i]) { eq = false; break; }
                }
                if (eq) return true;
            }
        }
        return false;
    }

    // ---- fast: O(1) HashMap lookup (fix) -----------------------------------

    static boolean fastMatchBin(Map<String, BinPattern> index, byte[] sample) {
        fastOps++;
        return index.containsKey(new String(sample));
    }

    // ---- benchmark driver --------------------------------------------------

    public static void main(String[] args) {
        final int P = 15;          // patterns: below the LRU threshold of 20
        final int REQUESTS = 10_000;

        List<BinPattern> patterns = new ArrayList<>();
        Map<String, BinPattern> index = new HashMap<>();

        for (int i = 0; i < P; i++) {
            byte[] data = ("pattern_key_" + i).getBytes();
            BinPattern bp = new BinPattern(data);
            patterns.add(bp);
            index.put(new String(data), bp);
        }

        // Worst-case: match the last pattern (maximum list walk)
        byte[] sample = ("pattern_key_" + (P - 1)).getBytes();

        slowOps = 0;
        fastOps = 0;

        for (int r = 0; r < REQUESTS; r++) {
            boolean s = slowMatchBin(patterns, sample);
            if (!s) throw new AssertionError("slow: pattern not found");
        }

        for (int r = 0; r < REQUESTS; r++) {
            boolean f = fastMatchBin(index, sample);
            if (!f) throw new AssertionError("fast: pattern not found");
        }

        long ratio = slowOps / Math.max(fastOps, 1);
        boolean pass = slowOps > fastOps * (P - 1);

        System.out.printf("haproxy-0001  slow=%d  fast=%d  ratio=%dx  %s%n",
                slowOps, fastOps, ratio, pass ? "PASS" : "FAIL");

        if (!pass) {
            System.err.printf("FAIL: expected slowOps(%d) > fastOps(%d) * %d%n",
                    slowOps, fastOps, P - 1);
            System.exit(1);
        }
    }
}