> ## Documentation Index
> Fetch the complete documentation index at: https://upstash-redis-1-18.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# ARRING

> Append values to a fixed-size ring.

Use `ARRING` to append values to an array that wraps around after a fixed number of slots.

The array is confined to indexes `0` through `<size> - 1`. Appends advance the same cursor [`ARINSERT`](/redis/commands/array/arinsert) uses, but wrap back to `0` on reaching the end, so the newest `<size>` values are kept and older ones are overwritten in place. That bounds the memory a stream of writes can consume without any trimming command, which is what makes it a fit for rolling windows such as the last N samples or the last N log lines.

The size is stored with the key and every call restates it. Calling `ARRING` with a different size reshapes the ring: the most recent values that still fit are kept and relaid from index `0`, and anything outside the new window is dropped. The reply is the index the last value was written to; read the window back with [`ARLASTITEMS`](/redis/commands/array/arlastitems), which follows the cursor and returns the values in write order.

See the [array command overview](/redis/commands/array/overview) for the data model these commands share.

## Syntax

```redis theme={null}
ARRING <key> <size> <value> [<value> ...]
```

## Arguments

| Argument  | Required | Repeatable | Description                                                   |
| --------- | -------- | ---------- | ------------------------------------------------------------- |
| `<key>`   | Yes      | No         | Array key targeted by the command.                            |
| `<size>`  | Yes      | No         | Number of slots in the ring. Must be greater than `0`.        |
| `<value>` | Yes      | Yes        | Value to append. Repeat to append several values in one call. |

## Important points

* The reply is the index the last value was written to, not the number of values written.
* Calling `ARRING` with a size different from the stored one rebuilds the ring, keeping the most recent values that fit in the new size.
* Writing more values than `<size>` in one call leaves only the last `<size>` of them.

## 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    | Integer, or bulk string when the index exceeds the signed 64-bit range |
| RESP3    | Integer, or Big number when the index exceeds the signed 64-bit range  |

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

## Examples

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

<AccordionGroup>
  <Accordion title="Redis CLI" icon="terminal">
    ```bash theme={null}
    ARRING my-array 100 hello world
    ```
  </Accordion>

  <Accordion title="@upstash/redis" icon="node-js" iconType="brands">
    <Note>
      This command is not supported yet in `@upstash/redis`.
    </Note>
  </Accordion>

  <Accordion title="upstash_redis" icon="python" iconType="brands">
    <Note>
      This command is not supported yet in `upstash_redis`.
    </Note>
  </Accordion>

  <Accordion title="ioredis" icon="node-js" iconType="brands">
    ```ts theme={null}
    import Redis from "ioredis";

    const redis = new Redis(process.env.REDIS_URL!);
    const result = await redis.arring("my-array", 100, "hello", "world");
    console.log(result);
    ```
  </Accordion>

  <Accordion title="node-redis" icon="node-js" iconType="brands">
    ```ts theme={null}
    import { createClient } from "redis";

    const client = await createClient({ url: process.env.REDIS_URL })
      .on("error", console.error)
      .connect();
    const result = await client.arRing("my-array", 100, ["hello", "world"]);
    console.log(result);
    ```
  </Accordion>

  <Accordion title="redis-py" icon="python" iconType="brands">
    ```python theme={null}
    import os
    import redis

    client = redis.from_url(os.environ["REDIS_URL"])
    result = client.arring("my-array", 100, "hello", "world")
    print(result)
    ```
  </Accordion>

  <Accordion title="go-redis" icon="golang" iconType="brands">
    ```go theme={null}
    package main

    import (
        "context"
        "fmt"
        "os"

        "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.ARRing(context.Background(), "my-array", 100, "hello", "world").Result()
        if err != nil {
            panic(err)
        }
        fmt.Println(result)
    }
    ```
  </Accordion>

  <Accordion title="jedis" icon="java" iconType="brands">
    ```java theme={null}
    import java.net.URI;

    import redis.clients.jedis.Jedis;

    try (Jedis jedis = new Jedis(new URI(System.getenv("REDIS_URL")))) {
      Object result = jedis.arring("my-array", 100, "hello", "world");
      System.out.println(result);
    }
    ```
  </Accordion>

  <Accordion title="redis-rs" icon="rust" iconType="brands">
    ```rust theme={null}
    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 mut command = redis::cmd("ARRING");
        command.arg("my-array");
        command.arg("100");
        command.arg("hello");
        command.arg("world");
        let result: redis::Value = command.query(&mut connection)?;
        println!("{result:?}");
        Ok(())
    }
    ```
  </Accordion>
</AccordionGroup>