Kay-Uwe Moosheimer created NIFI-8164:
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Summary: ConsumeMQTT validation bug
Key: NIFI-8164
URL: https://issues.apache.org/jira/browse/NIFI-8164
Project: Apache NiFi
Issue Type: Improvement
Affects Versions: 1.12.1
Reporter: Kay-Uwe Moosheimer
In ConsumeMQTT.java the following lines (196-200)
final boolean clientIDSet = context.getProperty(PROP_CLIENTID).isSet();
final boolean groupIDSet = context.getProperty(PROP_GROUPID).isSet();
if (clientIDSet && groupIDSet) {
results.add(new ValidationResult.Builder().subject("Client ID and Group
ID").valid(false).explanation("if client ID is not unique, multiple nodes
cannot join the consumer group").build());
}
are counterproductive.
It is true that a client ID must be unique for multiple mqtt clients to join a
consumer group.
If you enter the client ID as ${hostname()}-client, then the client ID is
unique (if you use this only once per node).
But this is not possible with the validation.
On the other hand it makes no sense if the client ID is random and you set the
session state to "resume session". A random client ID can never resume a
previous session.
In general it is also not advisable but only an add-on for lazy typists if you
don't use a unique client ID to auto generate a UUID. Because then only random
client IDs appear on the broker, which cannot be assigned to a certain
processor/node easily or not at all (monitoring nightmare).
Therefore please delete these lines, because ConsumeMQTT is applicable in this
way but not really in a proper way.
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