|
| 1 | +/* |
| 2 | + * JBoss, Home of Professional Open Source. |
| 3 | + * Copyright 2025 Red Hat, Inc., and individual contributors |
| 4 | + * as indicated by the @author tags. |
| 5 | + * |
| 6 | + * Licensed under the Apache License, Version 2.0 (the "License"); |
| 7 | + * you may not use this file except in compliance with the License. |
| 8 | + * You may obtain a copy of the License at |
| 9 | + * |
| 10 | + * http://www.apache.org/licenses/LICENSE-2.0 |
| 11 | + * |
| 12 | + * Unless required by applicable law or agreed to in writing, software |
| 13 | + * distributed under the License is distributed on an "AS IS" BASIS, |
| 14 | + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 15 | + * See the License for the specific language governing permissions and |
| 16 | + * limitations under the License. |
| 17 | + */ |
| 18 | +package io.undertow.server.handlers.ratelimit; |
| 19 | + |
| 20 | +import java.net.InetAddress; |
| 21 | +import java.net.InetSocketAddress; |
| 22 | +import java.util.concurrent.ConcurrentHashMap; |
| 23 | +import java.util.concurrent.TimeUnit; |
| 24 | +import java.util.concurrent.atomic.AtomicInteger; |
| 25 | + |
| 26 | +import org.xnio.XnioExecutor; |
| 27 | + |
| 28 | +import io.undertow.UndertowLogger; |
| 29 | +import io.undertow.server.HttpServerExchange; |
| 30 | +import io.undertow.util.WorkerUtils; |
| 31 | + |
| 32 | +/** |
| 33 | + * This is bit shift implementation of sliding window. Both rate and duration are converted to next 2^n in order to simply |
| 34 | + * bitshift values, rather than perform 10 based math and convert back into 2 base representation. This implementation of |
| 35 | + * {@link RateLimiter} has single, common window for all entries. For which keys are computed with bit shifting ops. This is not |
| 36 | + * precise, but has very low performance impact. |
| 37 | + */ |
| 38 | +public class BitShiftSingleWindowRateLimiter implements RateLimiter<HttpServerExchange> { |
| 39 | + // Single window to make it less resource hungry and simpler for first iteration. |
| 40 | + private int windowDuration; // duration in seconds. |
| 41 | + private int requestLimit; |
| 42 | + private volatile XnioExecutor.Key evictionKey; |
| 43 | + // numbers of bits to shift. This will be used to determine prefix for 'requestCounter'; Its based on duration next power of |
| 44 | + // 2; |
| 45 | + private int bitsToShift; |
| 46 | + // This map will store entries under key == prefix-IPAddress. where prefix is |
| 47 | + // "major" part of timestamp |
| 48 | + // Prefix math: |
| 49 | + // 10000 --> 10 |
| 50 | + // 10001 --> 10 |
| 51 | + // Next: 10+1 --> 11000 |
| 52 | + // In other words as long as bitsToShift wont cover ++, prefix will remain constant and allow fast and predictable |
| 53 | + // calculation of key. |
| 54 | + // Any key that does not start with prefix is outdated(window slid over it). |
| 55 | + // NOTE: this can be improved with Long as key and having upper store ~tstamp and lower having pure byte[] representation |
| 56 | + // of IP. Rest of logic would remain the same as for String key. |
| 57 | + // TODO: sanity check, this is IO thread, so no need for concurrent map and AtomicInteger ? |
| 58 | + private ConcurrentHashMap<String, AtomicInteger> requestCounter = new ConcurrentHashMap<String, AtomicInteger>(5000); |
| 59 | + private static final String PREFIX_SEPARATOR = "-"; |
| 60 | + private static final int TICK_BORDER = Integer.MAX_VALUE - 1; |
| 61 | + /** |
| 62 | + * Create bit shift limiter. Implementation will adjust values of both windowDuration and requestLimit, to adjust to next ^2. |
| 63 | + * Meaning duration of 33, will become 64. requestLimit will be adjusted to reflect this "stretch". |
| 64 | + * |
| 65 | + * @param windowDuration |
| 66 | + * @param requestLimit |
| 67 | + */ |
| 68 | + public BitShiftSingleWindowRateLimiter(final int windowDuration, final int requestLimit) { |
| 69 | + assert windowDuration > 0; |
| 70 | + assert requestLimit > 0; |
| 71 | + this.bitsToShift = determineBitShiftForDuration(windowDuration); |
| 72 | + this.windowDuration = Math.toIntExact(1L << this.bitsToShift) / 1000; |
| 73 | + // need to adjust requests, based on difference between bitshift duration and one that was passed here. |
| 74 | + // This is done to cover cases when nextP2 is not close to duration, for instance original duration 33s, will |
| 75 | + // switch to ~64, to have it work properly, we need to adjust limit as well. |
| 76 | + this.requestLimit = (int)(((float)this.windowDuration/windowDuration) * requestLimit); |
| 77 | + if(this.requestLimit == TICK_BORDER) { |
| 78 | + this.requestLimit--;//2M, but needs to be covered. Check {@link RateLimiter#getRequestLimit()} |
| 79 | + } |
| 80 | + |
| 81 | + } |
| 82 | + |
| 83 | + @Override |
| 84 | + public int getWindowDuration() { |
| 85 | + return this.windowDuration; |
| 86 | + } |
| 87 | + |
| 88 | + @Override |
| 89 | + public int getRequestLimit() { |
| 90 | + return this.requestLimit; |
| 91 | + } |
| 92 | + |
| 93 | + @Override |
| 94 | + public int timeToWindowSlide(final HttpServerExchange exchange) { |
| 95 | + // window is common so we ignore parameter. |
| 96 | + // nextPrefix->miliseconds-currentMilis/1000->s; |
| 97 | + final long currentMilis = System.currentTimeMillis(); |
| 98 | + return Math.toIntExact((((generatePrefix(currentMilis) + 1)<<bitsToShift) - currentMilis)/1000); |
| 99 | + } |
| 100 | + |
| 101 | + @Override |
| 102 | + public int increment(final HttpServerExchange exchange) { |
| 103 | + evictionCheck(exchange); |
| 104 | + |
| 105 | + final String ipAddress = getIPAddress(exchange, true); |
| 106 | + final String key = generateKey(ipAddress); |
| 107 | + AtomicInteger ai = requestCounter.computeIfAbsent(key, v -> new AtomicInteger()); |
| 108 | + return ai.accumulateAndGet(1, (value, upTick) -> { |
| 109 | + // JIC |
| 110 | + if (value < TICK_BORDER) { |
| 111 | + return value + upTick; //currentValue + 1(upTick) |
| 112 | + } else { |
| 113 | + return Integer.MAX_VALUE; //cap at Integer.MAX_VALUE, check RateLimi |
| 114 | + } |
| 115 | + }); |
| 116 | + } |
| 117 | + |
| 118 | + @Override |
| 119 | + public int current(final HttpServerExchange exchange) { |
| 120 | + final String ipAddress = getIPAddress(exchange, true); |
| 121 | + final String key = generateKey(ipAddress); |
| 122 | + AtomicInteger entry = requestCounter.get(key); |
| 123 | + if(entry != null) { |
| 124 | + return entry.get(); |
| 125 | + } else { |
| 126 | + return -1; |
| 127 | + } |
| 128 | + } |
| 129 | + |
| 130 | + private String getIPAddress(final HttpServerExchange exchange, final boolean warn) { |
| 131 | + final InetSocketAddress sourceAddress = exchange.getSourceAddress(); |
| 132 | + InetAddress address = sourceAddress.getAddress(); |
| 133 | + if (address == null) { |
| 134 | + // this can happen when we have an unresolved X-forwarded-for address |
| 135 | + // in this case we just return the IP of the balancer |
| 136 | + //TODO: this needs impr |
| 137 | + address = ((InetSocketAddress) exchange.getConnection().getPeerAddress()).getAddress(); |
| 138 | + if(warn) { |
| 139 | + UndertowLogger.REQUEST_LOGGER.rateLimitFailedToGetProperAddress(exchange.getRequestURI(), address.getHostAddress()); |
| 140 | + } |
| 141 | + } |
| 142 | + return address.getHostAddress(); |
| 143 | + } |
| 144 | + |
| 145 | + @Override |
| 146 | + public String getLimiterID() { |
| 147 | + return "bit-shift-window"; |
| 148 | + } |
| 149 | + |
| 150 | + @Override |
| 151 | + public RateLimitUnit getUnit() { |
| 152 | + return RateLimitUnit.REQUEST; |
| 153 | + } |
| 154 | + |
| 155 | + @Override |
| 156 | + public HttpServerExchange generateKey(HttpServerExchange e) { |
| 157 | + return e; |
| 158 | + } |
| 159 | + |
| 160 | + private void evictionCheck(HttpServerExchange exchange) { |
| 161 | + // we need to parasite on IO threads for eviction. |
| 162 | + XnioExecutor.Key key = this.evictionKey; |
| 163 | + if (key == null) { |
| 164 | + this.evictionKey = WorkerUtils.executeAfter(exchange.getIoThread(), new Runnable() { |
| 165 | + @Override |
| 166 | + public void run() { |
| 167 | + evictionKey = null; |
| 168 | + evictOldWindow(); |
| 169 | + } |
| 170 | + }, this.windowDuration, TimeUnit.SECONDS); |
| 171 | + } |
| 172 | + } |
| 173 | + |
| 174 | + private void evictOldWindow() { |
| 175 | + // evict entries that are not 'current' or 'current+1' - just in case eviction starts in one window and finish in next. |
| 176 | + // in such case 'current' will become stale already and will be evicted on next call. Thats fine. |
| 177 | + // prefix + 1 will translate into bitshift ++ |
| 178 | + final long currentPrefix = generatePrefix(); |
| 179 | + final String current = String.valueOf(currentPrefix); |
| 180 | + final String next = String.valueOf(currentPrefix + 1); |
| 181 | + |
| 182 | + ConcurrentHashMap.KeySetView<String, AtomicInteger> keys = requestCounter.keySet(); |
| 183 | + // remove obsolete keys |
| 184 | + keys.removeIf(k -> !k.startsWith(current) && !k.startsWith(next)); |
| 185 | + |
| 186 | + } |
| 187 | + |
| 188 | + private String generateKey(String ipAddress) { |
| 189 | + return generatePrefix() + PREFIX_SEPARATOR + ipAddress; |
| 190 | + } |
| 191 | + |
| 192 | + private long generatePrefix(long timeMilis) { |
| 193 | + return timeMilis >> this.bitsToShift; |
| 194 | + } |
| 195 | + |
| 196 | + private long generatePrefix() { |
| 197 | + return generatePrefix(System.currentTimeMillis()); |
| 198 | + } |
| 199 | + |
| 200 | + private int nextPowerOf2(final int v) { |
| 201 | + // this will return closest one bit, for 19, it will be 16. << 1 to get next highest |
| 202 | + final int higherOneBitValue = Integer.highestOneBit(v); |
| 203 | + if (v == higherOneBitValue) { |
| 204 | + return higherOneBitValue; |
| 205 | + } else { |
| 206 | + return higherOneBitValue << 1; |
| 207 | + } |
| 208 | + } |
| 209 | + |
| 210 | + private int determineBitShiftForDuration(final int duration) { |
| 211 | + // duration to milliseconds. |
| 212 | + final int nextP2 = nextPowerOf2(duration * 1000); |
| 213 | + // since its pure next power of 2, it has leading 1 and trailing zeros, which are equal to bit shift |
| 214 | + return Integer.numberOfTrailingZeros(nextP2); |
| 215 | + } |
| 216 | + |
| 217 | +} |
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