Troubleshooting the HELLO Command in Redis Software – Redis Knowledge Base

The HELLO command is used for RESP3 protocol negotiation in Redis Software. Support depends on your Redis version and how your cluster is configured. This article walks through Step-by-Step Solution, highlights key failure patterns under Troubleshooting, and includes Additional Resources.

Step-by-Step Solution

Check RESP3 and HELLO Command Compatibility

HELLO command availability
- Available starting with Redis Open Source 6.0
Full RESP3 support
- Only available in Redis Software 7.2.4 and later

Check Redis Software Version

Run the following command to check the Redis Server version:

redis-server --version
- Expected output format:
  
  Redis server v=7.2.0 sha=00000000:0 malloc=libc bits=64 build=abcdef12345678

Check Redis Software and Database Versions

Run the following command:

rladmin status extra all
- Check the following in the output:
  - Nodes section → Version column → Redis Software version
  - Databases section → Redis_Version column → Database version
Reference for version mapping:
- Database versions available for each Redis Software release can be found here

Test with redis-cli

From a terminal, connect using RESP3:

redis-cli
HELLO 3

If this succeeds, your backend supports RESP3.

To test RESP2 compatibility, run:

HELLO 2

or simply

HELLO

If RESP3 fails, confirm whether RESP3 is enabled on the proxy or database.
If needed, retry the connection using RESP2 by setting the protocol version explicitly in the client or continuing with RESP2-compatible commands.

Client Compatibility

Lettuce, redis-client (Ruby), and ioredis may issue HELLO by default.
Make sure your client library supports RESP3 and is configured for the correct protocol version.
For older server versions or databases that do not have RESP3 enabled force clients to use RESP2.

Authentication

If your Redis database requires authentication, include credentials in the HELLO call using the correct username. The default user is typically default, but this may vary depending on your RBAC setup.

HELLO 3 AUTH <username> <password>

Example using the default user (if enabled):

HELLO 3 AUTH default <password>

Check if RESP3 is Enabled

To verify RESP3 support in your Redis deployment, use the following methods:

At the cluster level:

rladmin info cluster

Look for the resp3_value field to confirm if RESP3 is enabled by default.

At the database level:

rladmin info db <database_name or db:<id>>

Check the resp3 field to see if RESP3 is enabled for the specific database.

In the Admin UI:

Go to the Configuration tab for the database.
Under RESP3 Support, confirm whether RESP3 is enabled.

For more details, refer to the official RESP compatibility reference: Enable RESP3

Proxy Layer Awareness

Redis Software deployments using proxies (especially on Redis Enterprise 6.x) may strip or block HELLO, even if the backend supports it.
Confirm if a proxy is in use and whether it supports RESP3 pass-through.