BLPOP - Upstash Documentation

Use BLPOP to pop an element from the head of the first non-empty list, blocking until one has an element or the timeout expires.

It is the blocking form of LPOP and it accepts several keys, which are checked in the order given, so earlier keys act as higher priority queues. The reply names the key the element came from together with the element itself, which matters when you are waiting on more than one queue.

The timeout is in seconds, may be fractional, and 0 waits indefinitely; when it expires the reply is null. Blocking lets a worker wait for work without polling, which cuts both latency and wasted commands. When several clients are blocked on the same key they are served in the order they started waiting.

Syntax#

BLPOP <key> [<key> ...] <timeout>

Arguments#

Argument	Required	Repeatable	Description
`<key>`	Yes	Yes	Redis key targeted by the command.
`<timeout>`	Yes	No	Seconds to block; `0` blocks indefinitely.

Important points#

A blocking form holds the request until data arrives or its timeout expires. Set the client/network timeout longer than the command timeout.

Response#

The reply reports the result of the operation. Error replies have the same shape in RESP2 and RESP3 and are surfaced as exceptions by the SDKs below.

Protocol	Reply
RESP2	Null bulk string or null array, or two-element key/value array
RESP3	Null, or two-element key/value array

Note

Client libraries often decode bulk strings, maps, sets, and numeric strings into language-native values. The table describes the Redis wire reply.

Examples#

TCP examples use the TLS REDIS_URL from the Upstash console. REST examples use UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN.

Redis CLI

BLPOP my-key 1.5

@upstash/redis

Note

This command is not supported yet in @upstash/redis.

upstash_redis

Note

This command is not supported yet in upstash_redis.

ioredis

import Redis from "ioredis";const redis = new Redis(process.env.REDIS_URL!);const result = await redis.blpop("my-key", "1.5");console.log(result);

node-redis

import { createClient } from "redis";const client = await createClient({ url: process.env.REDIS_URL })  .on("error", console.error)  .connect();const result = await client.blPop("my-key", 1.5);console.log(result);

redis-py

import osimport redisclient = redis.from_url(os.environ["REDIS_URL"])result = client.blpop(["my-key"], timeout=1.5)print(result)

go-redis

package mainimport (    "context"    "fmt"    "os"    "time"    "github.com/redis/go-redis/v9")func main() {    opts, err := redis.ParseURL(os.Getenv("REDIS_URL"))    if err != nil {        panic(err)    }    client := redis.NewClient(opts)    result, err := client.BLPop(context.Background(), 1500*time.Millisecond, "my-key").Result()    if err != nil {        panic(err)    }    fmt.Println(result)}

jedis

import java.net.URI;import redis.clients.jedis.Jedis;try (Jedis jedis = new Jedis(new URI(System.getenv("REDIS_URL")))) {  Object result = jedis.blpop(1.5, "my-key");  System.out.println(result);}

redis-rs

use redis::TypedCommands;fn main() -> redis::RedisResult<()> {    let url = std::env::var("REDIS_URL").expect("REDIS_URL is not set");    let client = redis::Client::open(url)?;    let mut connection = client.get_connection()?;    let result = connection.blpop("my-key", 1.5)?;    println!("{result:?}");    Ok(())}