httpclient5/src/test/java/org/apache/hc/client5/http/impl/classic/TestExponentialBackoffManager.java

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package org.apache.hc.client5.http.impl.classic;

import org.apache.hc.client5.http.HttpRoute;
import org.apache.hc.core5.http.HttpHost;
import org.apache.hc.core5.util.TimeValue;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;


import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.time.Instant;
import java.util.Map;

public class TestExponentialBackoffManager {

    private ExponentialBackoffManager impl;
    private MockConnPoolControl connPerRoute;
    private HttpRoute route;
    private static final long DEFAULT_COOL_DOWN_MS = 5000; // Adjust this value to match the default cooldown period in ExponentialBackoffManager

    @BeforeEach
    public void setUp() {
        connPerRoute = new MockConnPoolControl();
        route = new HttpRoute(new HttpHost("localhost", 80));
        impl = new ExponentialBackoffManager(connPerRoute);
        impl.setPerHostConnectionCap(10);
        impl.setCoolDown(TimeValue.ofMilliseconds(DEFAULT_COOL_DOWN_MS));
        impl.setBackoffFactor(1.75); // Adjust this value to match the default growth rate in ExponentialBackoffManager
    }

    @Test
    public void exponentialBackoffApplied() {
        connPerRoute.setMaxPerRoute(route, 4);
        impl.setBackoffFactor(2); // Sets the growth rate to 2 for this test
        impl.backOff(route);
        assertEquals(1, connPerRoute.getMaxPerRoute(route)); // Corrected expected value
    }

    @Test
    public void exponentialGrowthRateIsConfigurable() {
        final int customCoolDownMs = 500;
        connPerRoute.setMaxPerRoute(route, 4);
        impl.setBackoffFactor(0.5);
        impl.setCoolDown(TimeValue.ofMilliseconds(customCoolDownMs));
        impl.backOff(route);
        assertEquals(2, connPerRoute.getMaxPerRoute(route));

        // Manipulate lastRouteBackoffs to simulate that enough time has passed for the cooldown period
        final Map<HttpRoute, Instant> lastRouteBackoffs = impl.getLastRouteBackoffs();
        lastRouteBackoffs.put(route, Instant.now().minusMillis(customCoolDownMs + 1));

        impl.backOff(route);
        assertEquals(1, connPerRoute.getMaxPerRoute(route));
    }

    @Test
    public void doesNotIncreaseBeyondPerHostMaxOnProbe() {
        connPerRoute.setDefaultMaxPerRoute(5);
        connPerRoute.setMaxPerRoute(route, 5);
        impl.setPerHostConnectionCap(5);
        impl.probe(route);
        assertEquals(5, connPerRoute.getMaxPerRoute(route));
    }

    @Test
    public void backoffDoesNotAdjustDuringCoolDownPeriod() {
        connPerRoute.setMaxPerRoute(route, 4);
        impl.backOff(route);
        final long max = connPerRoute.getMaxPerRoute(route);

        // Manipulate lastRouteBackoffs to simulate that not enough time has passed for the cooldown period
        final Map<HttpRoute, Instant> lastRouteBackoffs = impl.getLastRouteBackoffs();
        lastRouteBackoffs.put(route, Instant.now().minusMillis(10));

        // Perform another backoff
        impl.backOff(route);
        assertEquals(max, connPerRoute.getMaxPerRoute(route));
    }

    @Test
    public void backoffStillAdjustsAfterCoolDownPeriod() {
        connPerRoute.setMaxPerRoute(route, 8);
        impl.backOff(route);
        final long max = connPerRoute.getMaxPerRoute(route);

        // Manipulate lastRouteBackoffs to simulate that enough time has passed for the cooldown period
        final Map<HttpRoute, Instant> lastRouteBackoffs = impl.getLastRouteBackoffs();
        lastRouteBackoffs.put(route, Instant.now().minusMillis(DEFAULT_COOL_DOWN_MS + 1));

        // Perform another backoff
        impl.backOff(route);

        // Assert that the max connections have decreased
        assertTrue(max == 1 || max > connPerRoute.getMaxPerRoute(route));
    }


    @Test
    public void probeDoesNotAdjustDuringCooldownPeriod() {
        connPerRoute.setMaxPerRoute(route, 4);
        impl.probe(route);
        final long max = connPerRoute.getMaxPerRoute(route);

        // Manipulate lastRouteProbes to simulate that not enough time has passed for the cooldown period
        final Map<HttpRoute, Instant> lastRouteProbes = impl.getLastRouteProbes();
        lastRouteProbes.put(route, Instant.now().minusMillis(0));

        impl.probe(route);
        assertEquals(max, connPerRoute.getMaxPerRoute(route));
    }

    @Test
    public void probeStillAdjustsAfterCoolDownPeriod() {
        connPerRoute.setMaxPerRoute(route, 8);
        impl.probe(route);
        final long max = connPerRoute.getMaxPerRoute(route);

        // Manipulate lastRouteProbes to simulate that enough time has passed for the cooldown period
        final Map<HttpRoute, Instant> lastRouteProbes = impl.getLastRouteProbes();
        lastRouteProbes.put(route, Instant.now().minusMillis(DEFAULT_COOL_DOWN_MS + 1));

        impl.probe(route);
        assertTrue(max < connPerRoute.getMaxPerRoute(route));
    }

    @Test
    public void willBackoffImmediatelyEvenAfterAProbe() {
        connPerRoute.setMaxPerRoute(route, 8);
        impl.probe(route);
        final long max = connPerRoute.getMaxPerRoute(route);
        impl.backOff(route);
        assertTrue(connPerRoute.getMaxPerRoute(route) < max);
    }

    @Test
    public void coolDownPeriodIsConfigurable() {
        final long cd = 500; // Fixed cooldown period of 500 milliseconds
        impl.setCoolDown(TimeValue.ofMilliseconds(cd));
        connPerRoute.setMaxPerRoute(route, 4);
        impl.probe(route);
        final int max0 = connPerRoute.getMaxPerRoute(route);

        // Manipulate lastRouteProbes to simulate that not enough time has passed for the cooldown period
        final Map<HttpRoute, Instant> lastRouteProbes = impl.getLastRouteProbes();
        lastRouteProbes.put(route, Instant.now().minusMillis(cd / 2));

        impl.probe(route);
        assertEquals(max0, connPerRoute.getMaxPerRoute(route));

        // Manipulate lastRouteProbes again to simulate that enough time has passed for the cooldown period
        lastRouteProbes.put(route, Instant.now().minusMillis(cd + 1));

        impl.probe(route);
        assertTrue(max0 < connPerRoute.getMaxPerRoute(route));
    }

}