BLMOVE - Upstash Documentation

Use BLMOVE to move an element from one list to another, blocking until the source has an element or the timeout expires.

It is the blocking form of LMOVE: when the source list is not empty it behaves identically and returns immediately, and when it is empty the connection waits instead of returning null. The timeout is given in seconds, may be fractional, and 0 waits indefinitely. If several clients are waiting on the same key, the one that has been waiting longest is served first.

Because the element is never outside a list, this is the standard way to build a reliable queue: a worker blocks until work appears, atomically moves it to a processing list, and deletes it from there when done, so an interrupted job can be recovered instead of lost.

Syntax#

BLMOVE <source> <destination> (LEFT | RIGHT) (LEFT | RIGHT) <timeout>

Arguments#

Argument	Required	Repeatable	Description
`<source>`	Yes	No	Redis key used as source.
`<destination>`	Yes	No	Redis key used as destination.
`(LEFT \| RIGHT)`	Yes	No	Which end of the source list the element is taken from: `LEFT` (head) or `RIGHT` (tail).
`(LEFT \| RIGHT)`	Yes	No	Which end of the destination list the element is pushed onto: `LEFT` (head) or `RIGHT` (tail).
`<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	Bulk string or Null bulk string or null array
RESP3	Bulk string or Null

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

BLMOVE source-key destination-key LEFT LEFT 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.blmove("source-key", "destination-key", "LEFT", "LEFT", "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.blMove("source-key", "destination-key", "LEFT", "LEFT", 1.5);console.log(result);

redis-py

import osimport redisclient = redis.from_url(os.environ["REDIS_URL"])result = client.blmove("source-key", "destination-key", 1.5, "LEFT", "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.BLMove(context.Background(), "source-key", "destination-key", "LEFT", "LEFT", 1500*time.Millisecond).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.blmove("source-key", "destination-key", redis.clients.jedis.args.ListDirection.LEFT, redis.clients.jedis.args.ListDirection.LEFT, 1.5);  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.blmove(        "source-key",        "destination-key",        Direction::Left,        Direction::Left,        1.5,    )?;    println!("{result:?}");    Ok(())}