Federico Mariani created CAMEL-25888:
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Summary: camel-pubnub - the producer should not use the consumer's
channel header
Key: CAMEL-25888
URL: https://issues.apache.org/jira/browse/CAMEL-25888
Project: Camel
Issue Type: Bug
Components: camel-pubnub
Reporter: Federico Mariani
Fix For: 4.24.0, 4.22.3, 4.18.6
h3. Current behaviour
The PubNub consumer sets the {{CamelPubNubChannel}} header
({{PubNubConstants.CHANNEL}}) to the channel each received message or presence
event arrived on ({{PubNubConsumer}}). The same header is also read by the
producer: {{PubNubProducer.getChannel()}} prefers {{CamelPubNubChannel}} over
the {{channel}} configured on the endpoint, for every operation (publish, fire,
getHistory, getState, setState, hereNow), and there is no option to turn this
off.
As a result, a route that consumes from one PubNub endpoint and sends to a
second PubNub endpoint does not use the second endpoint's configured channel.
The exchange still carries the consumer's {{CamelPubNubChannel}} header, so the
producer sends to the channel the message was received on. With a wildcard
({{foo.*}}) or a comma-separated channel list on the consumer, the channel used
by the producer changes from message to message.
{code:java}
from("pubnub:inbound.*?subscribeKey=...")
.to("pubnub:outbound?publishKey=...&subscribeKey=...");
// today the message is published to the channel it was received on (e.g.
inbound.a),
// not to "outbound"
{code}
The consumer header is metadata about where a message came from; it should not
decide where a downstream producer sends it. Other components keep these two
concerns apart (for example camel-kafka's {{kafka.TOPIC}} /
{{kafka.OVERRIDE_TOPIC}}).
h3. Expected behaviour
* The producer uses the channel configured on its endpoint.
* A new producer header, {{CamelPubNubOverrideChannel}}
({{PubNubConstants.OVERRIDE_CHANNEL}}), lets a route choose a different channel
explicitly.
* The consumer keeps setting {{CamelPubNubChannel}} as before.
h3. Proposed change
* {{PubNubConstants}}: keep {{CHANNEL}} ({{CamelPubNubChannel}}) as consumer
metadata; add {{OVERRIDE_CHANNEL = "CamelPubNubOverrideChannel"}} with
{{@Metadata(label = "producer", description = "The channel to use instead of
the channel configured on the endpoint.")}}.
* {{PubNubProducer.getChannel()}}: read only {{CamelPubNubOverrideChannel}},
falling back to {{PubNubConfiguration.getChannel()}}; it no longer reads
{{CamelPubNubChannel}}.
* Regenerate {{pubnub.json}}, the catalog and the endpoint DSL header constants.
* Upgrade guide: routes that set {{CamelPubNubChannel}} to pick the producer's
channel must use {{CamelPubNubOverrideChannel}} instead (4.24, and the 4.22.3
and 4.18.6 entries).
h3. Tests
* {{PubNubPublishTest}}: an exchange carrying {{CamelPubNubChannel}} is
published to the endpoint's configured channel; {{CamelPubNubOverrideChannel}}
selects the channel when set.
* A consumer-to-producer route test: a message received on one channel and
forwarded to a second pubnub endpoint is published to that endpoint's
configured channel.
* Existing consumer assertions on {{CamelPubNubChannel}}
({{PubNubSubscriberTest}}, {{PubNubPresenceTest}}) stay unchanged.
The behaviour dates back to the first version of the component and is the same
on main, camel-4.22.x and camel-4.18.x.
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