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HELLO

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HELLO [protover [AUTH username password] [SETNAME clientname]]
Group
Connection
Complexity
O(1)
Arity
-1 (at least 1 words, counting the command name)
Flags
fast, no-auth, loading, stale
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HELLO is usually the first command a modern client library sends. It switches the connection to the protocol version you ask for (2 for RESP2, 3 for RESP3) and replies with a short description of the server. Without arguments it keeps the current protocol and only returns the description.

The AUTH and SETNAME options let a client log in and name the connection in the same round trip. They can only follow a protover.

Options

Section titled “Options”
Option Effect
protover 2 or 3. Any other value is refused with NOPROTO unsupported protocol version.
AUTH username password Log in as this ACL user first, as AUTH does. Use default as the user name for a requirepass password.
SETNAME clientname Name the connection, as CLIENT SETNAME does. The name cannot contain spaces or non-printable characters.

If the server needs a password and the connection is not authenticated, HELLO without AUTH fails with this error, and the protocol is not changed:

NOAUTH HELLO must be called with the client already authenticated, otherwise the HELLO <proto> AUTH <user> <pass> option can be used to authenticate the client and select the RESP protocol version at the same time

Return value

Section titled “Return value”

Seven fields: a map in RESP3, a flat array of field and value pairs in RESP2. The reply already uses the protocol you selected.

Field Value
server hotkv
version The Redis version HotKV is compatible with (8.4.0). Client libraries choose features by it. The HotKV release is in the hotkv_version field of INFO server.
proto The protocol now in use, 2 or 3.
id The connection id, as CLIENT ID returns it.
mode standalone or cluster.
role master or replica.
modules Always an empty array. HotKV has no module system.

Other errors: WRONGPASS when AUTH fails, ERR syntax error for an unknown or incomplete option, and the name error of CLIENT SETNAME.

Examples

Section titled “Examples”
127.0.0.1:6379> HELLO 3
1# "server" => "hotkv"
2# "version" => "8.4.0"
3# "proto" => (integer) 3
4# "id" => (integer) 7
5# "mode" => "standalone"
6# "role" => "master"
7# "modules" => (empty array)
127.0.0.1:6379> HELLO 2 AUTH default s3cret SETNAME worker-1
 1) "server"
 2) "hotkv"
 3) "version"
 4) "8.4.0"
 5) "proto"
 6) (integer) 2
 7) "id"
 8) (integer) 7
 9) "mode"
10) "standalone"
11) "role"
12) "master"
13) "modules"
14) (empty array)
127.0.0.1:6379> HELLO 4
(error) NOPROTO unsupported protocol version

Compatibility

Section titled “Compatibility”

Same options and error replies as Redis 7 and Valkey 8. The server field is hotkv, and modules is always empty. See RESP3 for how replies differ between the two protocols.

See also

Section titled “See also”

AUTH, CLIENT SETNAME, CLIENT INFO, RESET, PING