BLMPOP - Upstash Documentation

Use BLMPOP to pop elements from the first non-empty list among several, blocking until one has elements or the timeout expires.

It is the blocking form of LMPOP: keys are examined in the order given, so listing a high priority queue first drains it before the others are considered, LEFT or RIGHT chooses the end, and COUNT sets how many elements to take. The reply names the key that was popped from along with the elements.

The timeout is in seconds, may be fractional, and 0 waits indefinitely; when it expires the reply is null. This is the command to reach for when one worker serves several queues of differing priority.

Syntax#

BLMPOP <timeout> <numkeys> <key> [<key> ...] (LEFT | RIGHT) [COUNT <count>]

Arguments#

Argument	Required	Repeatable	Description
`<timeout>`	Yes	No	Seconds to block; `0` blocks indefinitely.
`<numkeys>`	Yes	No	Number of key arguments that follow.
`<key>`	Yes	Yes	Redis key targeted by the command.
`(LEFT \| RIGHT)`	Yes	No	Which end to pop from: `LEFT` (head) or `RIGHT` (tail).
`COUNT <count>`	No	No	Maximum number of elements to pop.

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 array: key and array of values
RESP3	Null, or two-element array: key and array of values

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

BLMPOP 1.5 1 my-key LEFT

@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.blmpop("1.5", "1", "my-key", "LEFT");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.blmPop(1.5, "my-key", "LEFT");console.log(result);

redis-py

import osimport redisclient = redis.from_url(os.environ["REDIS_URL"])result = client.blmpop(1.5, 1, "my-key", direction="LEFT")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.BLMPop(context.Background(), 1500*time.Millisecond, "LEFT", 0, "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.blmpop(1.5, redis.clients.jedis.args.ListDirection.LEFT, "my-key");  System.out.println(result);}

redis-rs

use redis::{Direction, 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.blmpop(1.5, 1, "my-key", Direction::Left, 1)?;    println!("{result:?}");    Ok(())}