Tair Serverless KV client-side throttling - Tair (Redis® OSS-Compatible)

When a Tair Serverless KV instance experiences a traffic spike, it automatically scales out to twice its original peak capacity. By default, requests that exceed the original peak capacity are queued during the scale-out process. This behavior is consistent with open source Redis. To have throttled requests return an error immediately, you can set the return-err-when-throttle parameter to yes. Throttled requests then return a THROTTLED error. You can retry or discard requests that receive this error. The following code samples show how to retry requests.

Jedis

Import the Jedis dependency.

<!-- This example uses version 5.2.0. -->
<dependency>
    <groupId>redis.clients</groupId>
    <artifactId>jedis</artifactId>
    <version>5.2.0</version>
</dependency>

Code sample.

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;
import redis.clients.jedis.exceptions.JedisException;

public class JedisThrottledTest {
    private static final Logger logger = LoggerFactory.getLogger(JedisThrottledTest.class);

    private static final int MAX_RETRY = 10; // Maximum retry attempts

    public static void main(String[] args) {
        if (args.length < 3) {
            System.out.println("Usage: java -jar JedisThrottledTest.jar <host> <port> <password>");
            return;
        }

        String host = args[0];
        int port = Integer.parseInt(args[1]);
        String password = args[2];

        JedisPoolConfig poolConfig = new JedisPoolConfig();
        poolConfig.setMaxTotal(32);
        poolConfig.setMaxIdle(32);
        poolConfig.setMinIdle(16);

        JedisPool jedisPool = new JedisPool(poolConfig, host, port, 3000, password);
        for (int i = 0; i < 4; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    for (int i = 0; i < Integer.MAX_VALUE; i++) {
                        executeWithRetry(jedisPool, "key" + i, "value" + i);
                    }
                }
            }).start();
        }
    }

    private static void executeWithRetry(JedisPool jedisPool, String key, String value) {
        int retryCount = 0;
        while (retryCount < MAX_RETRY) {
            try (Jedis jedis = jedisPool.getResource()) {
                jedis.set(key, value);
                break;
            } catch (JedisException e) {
                if (e.getMessage().contains("THROTTLED")) {
                    logger.info("Throttled error occurred (attempt " + retryCount + "): " + e.getMessage());
                    retryCount++;
                    if (retryCount >= MAX_RETRY) {
                        logger.info("Max retry attempts reached.");
                        throw e;
                    }
                    try {
                        int sleepTime = (int)Math.pow(2, retryCount);
                        Thread.sleep(sleepTime * 1000);
                    } catch (InterruptedException ie) {
                        Thread.currentThread().interrupt();
                        throw new RuntimeException("Thread interrupted during retry delay", ie);
                    }
                } else {
                    throw e;
                }
            }
        }
    }
}

Valkey-java

Import the Valkey-java dependency.

Important

Use valkey-java version 5.4.0 or later.

<dependency>
    <groupId>io.valkey</groupId>
    <artifactId>valkey-java</artifactId>
    <version>5.4.0</version>
</dependency>

Code sample.

import java.time.Duration;

import io.valkey.DefaultJedisClientConfig;
import io.valkey.ExceptionHandler;
import io.valkey.HostAndPort;
import io.valkey.UnifiedJedis;
import io.valkey.providers.PooledConnectionProvider;
import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ThrottledTest {
    private static final Logger logger = LoggerFactory.getLogger(ThrottledTest.class);

    /**
     * Implements exponential backoff.
     */
    static class ExponentialBackoffCallback implements ExceptionHandler.ErrorCallback {
        private int attempt = 0;

        @Override
        public void onError(String errorMessage) {
            int sleepTime = (int)Math.pow(2, attempt);
            try {
                logger.info("Sleeping for " + sleepTime + " seconds before handling: " + errorMessage);
                Thread.sleep(sleepTime * 1000);
            } catch (InterruptedException ie) {
                // Ignore the error.
            }
            attempt++;
        }
    }

    public static void main(String[] args) {
        if (args.length < 3) {
            System.out.println("Usage: java -jar ThrottledTest.jar <host> <port> <password>");
            return;
        }

        String host = args[0];
        int port = Integer.parseInt(args[1]);
        String password = args[2];

        GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig();
        poolConfig.setMaxTotal(32);
        poolConfig.setMaxIdle(32);
        poolConfig.setMinIdle(16);

        int maxAttempts = 100; // Maximum retry attempts
        Duration maxTotalRetriesDuration = Duration.ofSeconds(1000); // Maximum total duration for retries
        PooledConnectionProvider provider = new PooledConnectionProvider(new HostAndPort(host, port),
            DefaultJedisClientConfig.builder().password(password).build(), poolConfig);

        ExceptionHandler handler = new ExceptionHandler();
        handler.register(
            message -> message.contains("THROTTLED"),
            new ExponentialBackoffCallback()
        );

        UnifiedJedis unifiedJedis = new UnifiedJedis(provider, maxAttempts, maxTotalRetriesDuration, handler);
        for (int i = 0; i < 4; i++) { // Use four threads to generate high QPS.
            new Thread(new Runnable() {
                @Override
                public void run() {
                    for (int i = 0; i < Integer.MAX_VALUE; i++) {
                        try {
                            unifiedJedis.set("" + i, "" + i);
                        } catch (Exception e) {
                            logger.error("Error occurred {}", e.getMessage());
                        }
                    }
                }
            }).start();
        }
    }
}

redis-py

This example uses redis-py version 6.1.1.

import sys
import time
import threading
import logging
from redis import Redis, RedisError

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

MAX_RETRY = 10  # Maximum retry attempts

def execute_with_retry(redis_client, key, value):
    retry_count = 0
    while retry_count < MAX_RETRY:
        try:
            redis_client.set(key, value)
            break  # If successful, exit the loop.
        except RedisError as e:
            if "THROTTLED" in str(e):
                logger.info(f"Throttled error occurred (attempt {retry_count}): {e}")
                retry_count += 1
                if retry_count >= MAX_RETRY:
                    logger.info("Max retry attempts reached.")
                    raise e
                sleep_time = 2 ** retry_count
                time.sleep(sleep_time)
            else:
                logger.error(f"Non-throttled Redis error: {e}")
                raise e

def worker(redis_client):
    i = 0
    while True:
        try:
            execute_with_retry(redis_client, f"key{i}", f"value{i}")
            i += 1
        except Exception as e:
            logger.exception(f"Unexpected error in worker: {e}")
            time.sleep(1)  # Avoid tight loop in case of persistent errors

def main():
    if len(sys.argv) < 4:
        print("Usage: python script.py <host> <port> <password>")
        return

    host = sys.argv[1]
    port = int(sys.argv[2])
    password = sys.argv[3]

    redis_client = Redis(
        host=host,
        port=port,
        password=password,
        socket_timeout=3,
        decode_responses=True
    )

    # Test the connection.
    try:
        redis_client.ping()
        logger.info("Successfully connected to Redis")
    except RedisError as e:
        logger.error(f"Failed to connect to Redis: {e}")
        return

    # Create and start 10 threads.
    threads = []
    for i in range(10):
        thread = threading.Thread(target=worker, args=(redis_client,))
        thread.daemon = True
        thread.start()
        threads.append(thread)
        logger.info(f"Started worker thread {i}")

    # Keep the main thread running.
    try:
        while True:
            time.sleep(1)
    except KeyboardInterrupt:
        logger.info("Program interrupted. Exiting...")

    # Wait for all threads to complete.
    for thread in threads:
        thread.join()

if __name__ == "__main__":
    main()