Claus Ibsen created CAMEL-25515:
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Summary: camel-jgroups-raft - the consumer's role change events do
not handle the Learner role
Key: CAMEL-25515
URL: https://issues.apache.org/jira/browse/CAMEL-25515
Project: Camel
Issue Type: Bug
Components: camel-jgroups
Reporter: Claus Ibsen
The jgroups-raft consumer with {{enableRoleChangeEvents=true}} does not handle
the {{Learner}} role.
{{CamelRoleChangeListener.roleChanged}} only maps {{Leader}} and {{Follower}},
and throws {{JGroupsRaftException("Role [Learner] unknown.")}} for anything
else:
{code:java}
switch (role) {
case Leader: ... JGroupsRaftEventType.LEADER
case Follower: ... JGroupsRaftEventType.FOLLOWER
default:
throw new JGroupsRaftException("Role [" + role + "] unknown.");
}
{code}
jgroups-raft 1.1.x (Camel uses 1.1.4.Final) has a third role,
{{org.jgroups.protocols.raft.Role.Learner}}. {{Learner extends Follower}}: it
replicates the log but cannot vote or become leader. {{RAFT._removeServer()}}
moves a node that is removed from the members straight from {{Leader}} to
{{Learner}}, without passing through {{Follower}}.
RAFT catches the exception thrown by the listener, so nothing crashes, but the
consumer route gets no event when its node steps down from leader. A route that
starts work on {{LEADER}} and stops it on {{FOLLOWER}} keeps acting as leader
after the node was removed.
{{JGroupsRaftEventType}} has no {{LEARNER}} value either.
h3. Proposal
* Add {{JGroupsRaftEventType.LEARNER}} and send it for {{Role.Learner}} (or, if
a new event type is not wanted, send {{FOLLOWER}} for it, since a learner is a
non-voting follower).
* Do not throw for an unknown role; log it at WARN so a future role does not
silently drop events.
* Document the new event type in the component docs, and add a unit test that
calls {{roleChanged(Role.Learner)}}.
h3. Context
Found while reviewing https://github.com/apache/camel/pull/27613 (CAMEL-25488 /
CAMEL-24598), which fixes the same gap in {{JGroupsRaftClusterView}} (the
cluster service / master component side) but not in the consumer's
{{CamelRoleChangeListener}}.
_Created by Claude Code on behalf of Claus Ibsen._
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