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Fix rate limiter

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Time reported by nanoTime is arbitrarily and could include negative numbers
This commit is contained in:
games647
2022-01-14 14:03:14 +01:00
parent e0f823cbe4
commit 36c9ae2465
4 changed files with 109 additions and 16 deletions
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23
core/src/main/java/com/github/games647/fastlogin/core/RateLimiter.java
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@ -25,6 +25,8 @@
*/
package com.github.games647.fastlogin.core;
import com.google.common.base.Ticker;
import java.util.Arrays;
/**
@ -33,16 +35,22 @@ import java.util.Arrays;
*/
public class RateLimiter {
private final Ticker ticker;
private final long[] requests;
private final long expireTime;
private int position;
public RateLimiter(int maxLimit, long expireTime) {
public RateLimiter(Ticker ticker, int maxLimit, long expireTime) {
this.ticker = ticker;
this.requests = new long[maxLimit];
this.expireTime = expireTime;
// fill the array with the lowest values, so that the first uninitialized values will always expire
Arrays.fill(requests, Long.MIN_VALUE);
// fill the array with expired entry, because nanoTime could overflow and include negative numbers
long nowMilli = ticker.read() / 1_000_000;
long initialVal = nowMilli - expireTime;
Arrays.fill(requests, initialVal);
}
/**
@ -52,15 +60,12 @@ public class RateLimiter {
*/
public boolean tryAcquire() {
// current time millis is not monotonic - it can jump back depending on user choice or NTP
long now = System.nanoTime() / 1_000_000;
// after this the request should be expired
long toBeExpired = now - expireTime;
long nowMilli = ticker.read() / 1_000_000;
synchronized (this) {
// having synchronized will limit the amount of concurrency a lot
long oldest = requests[position];
if (oldest < toBeExpired) {
requests[position] = now;
if (nowMilli - oldest >= expireTime) {
requests[position] = nowMilli;
position = (position + 1) % requests.length;
return true;
}

3
core/src/main/java/com/github/games647/fastlogin/core/shared/FastLoginCore.java
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@ -35,6 +35,7 @@ import com.github.games647.fastlogin.core.hooks.PasswordGenerator;
import com.github.games647.fastlogin.core.storage.MySQLStorage;
import com.github.games647.fastlogin.core.storage.SQLStorage;
import com.github.games647.fastlogin.core.storage.SQLiteStorage;
import com.google.common.base.Ticker;
import com.google.common.net.HostAndPort;
import com.zaxxer.hikari.HikariConfig;
@ -122,7 +123,7 @@ public class FastLoginCore<P extends C, C, T extends PlatformPlugin<C>> {
expireTime = MAX_EXPIRE_RATE;
}
rateLimiter = new RateLimiter(maxCon, expireTime);
rateLimiter = new RateLimiter(Ticker.systemTicker(), maxCon, expireTime);
Set<Proxy> proxies = config.getStringList("proxies")
.stream()
.map(HostAndPort::fromString)

23
core/src/test/java/com/github/games647/fastlogin/core/FakeTicker.java Normal file
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@ -0,0 +1,23 @@
package com.github.games647.fastlogin.core;
import com.google.common.base.Ticker;
import java.time.Duration;
public class FakeTicker extends Ticker {
private long timestamp;
public FakeTicker(long initial) {
timestamp = initial;
}
@Override
public long read() {
return timestamp;
}
public void add(Duration duration) {
timestamp += duration.toNanos();
}
}

76
core/src/test/java/com/github/games647/fastlogin/core/RateLimiterTest.java
View File

@ -25,6 +25,7 @@
*/
package com.github.games647.fastlogin.core;
import java.time.Duration;
import java.util.concurrent.TimeUnit;
import org.junit.Test;
@ -43,14 +44,34 @@ public class RateLimiterTest {
public void allowExpire() throws InterruptedException {
int size = 3;
FakeTicker ticker = new FakeTicker(5_000_000L);
// run twice the size to fill it first and then test it
RateLimiter rateLimiter = new RateLimiter(size, 0);
RateLimiter rateLimiter = new RateLimiter(ticker, size, 0);
for (int i = 0; i < size; i++) {
assertTrue("Filling up", rateLimiter.tryAcquire());
}
for (int i = 0; i < size; i++) {
Thread.sleep(1);
ticker.add(Duration.ofSeconds(1));
assertTrue("Should be expired", rateLimiter.tryAcquire());
}
}
@Test
public void allowExpireNegative() throws InterruptedException {
int size = 3;
FakeTicker ticker = new FakeTicker(-5_000_000L);
// run twice the size to fill it first and then test it
RateLimiter rateLimiter = new RateLimiter(ticker, size, 0);
for (int i = 0; i < size; i++) {
assertTrue("Filling up", rateLimiter.tryAcquire());
}
for (int i = 0; i < size; i++) {
ticker.add(Duration.ofSeconds(1));
assertTrue("Should be expired", rateLimiter.tryAcquire());
}
}
@ -62,8 +83,28 @@ public class RateLimiterTest {
public void shouldBlock() {
int size = 3;
FakeTicker ticker = new FakeTicker(5_000_000L);
// fill the size
RateLimiter rateLimiter = new RateLimiter(size, TimeUnit.SECONDS.toMillis(30));
RateLimiter rateLimiter = new RateLimiter(ticker, size, TimeUnit.SECONDS.toMillis(30));
for (int i = 0; i < size; i++) {
assertTrue("Filling up", rateLimiter.tryAcquire());
}
assertFalse("Should be full and no entry should be expired", rateLimiter.tryAcquire());
}
/**
* Too many requests
*/
@Test
public void shouldBlockNegative() {
int size = 3;
FakeTicker ticker = new FakeTicker(-5_000_000L);
// fill the size
RateLimiter rateLimiter = new RateLimiter(ticker, size, TimeUnit.SECONDS.toMillis(30));
for (int i = 0; i < size; i++) {
assertTrue("Filling up", rateLimiter.tryAcquire());
}
@ -76,17 +117,40 @@ public class RateLimiterTest {
*/
@Test
public void blockedNotAdded() throws InterruptedException {
FakeTicker ticker = new FakeTicker(5_000_000L);
// fill the size - 100ms should be reasonable high
RateLimiter rateLimiter = new RateLimiter(1, 100);
RateLimiter rateLimiter = new RateLimiter(ticker, 1, 100);
assertTrue("Filling up", rateLimiter.tryAcquire());
Thread.sleep(50);
ticker.add(Duration.ofMillis(50));
// still is full - should fail
assertFalse("Expired too early", rateLimiter.tryAcquire());
// wait the remaining time and add a threshold, because
Thread.sleep(50 + THRESHOLD_MILLI);
ticker.add(Duration.ofMillis(50));
assertTrue("Request not released", rateLimiter.tryAcquire());
}
/**
* Blocked attempts shouldn't replace existing ones.
*/
@Test
public void blockedNotAddedNegative() throws InterruptedException {
FakeTicker ticker = new FakeTicker(-5_000_000L);
// fill the size - 100ms should be reasonable high
RateLimiter rateLimiter = new RateLimiter(ticker, 1, 100);
assertTrue("Filling up", rateLimiter.tryAcquire());
ticker.add(Duration.ofMillis(50));
// still is full - should fail
assertFalse("Expired too early", rateLimiter.tryAcquire());
// wait the remaining time and add a threshold, because
ticker.add(Duration.ofMillis(50));
assertTrue("Request not released", rateLimiter.tryAcquire());
}
}