[CASSANDRA-16940] Confusing ProtocolException msg Invalid or unsupported protocol version (4)

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Cannot Reproduce
• Component/s: Messaging/Client
• Bug Category: Correctness
• Severity: Normal
• Complexity: Normal
• Discovered By: User Report
• Platform: All
• Assignee: Unassigned
• Reporter: Brad Schoening
• Created: 09/Sep/21 21:49
• Updated: 10/Aug/22 01:43
• Resolved: 10/Aug/22 01:43

Description

The following warning was seen frequently after upgrading from 3.0.15 to 3.11.11 in the cassandra.log:

ProtocolException: Invalid or unsupported protocol version (4); supported versions are (3/v3, 4/v4, 5/v5-beta)

It is at best unclear, or maybe a bug in the code throwing this exception stating version '4' not supported but 4/v4 is.

from org/apache/cassandra/transport/ProtocolVersion.java

public static String invalidVersionMessage(int version)

{ return String.format("Invalid or unsupported protocol version (%d); supported versions are (%s)", version, String.join(", ", ProtocolVersion.supportedVersions())); }

We later found invalid IP addresses in the system.peers table and once removed, this exception went away.