1. Connection Failure

1.1 Broker Unreachable

• Check bootstrapServers
• Container network (DNS, Port Mapping)
• Broker listener configuration (advertised.listeners)

1.2 ACL/Auth Failure

• Mechanism match (PLAIN/SCRAM)
• User produce/consume permission on topic
• TLS CA correctness, hostname verification enabled

See: Kafka Connection & Security

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2. Connected but No Data

Prioritize confirming:

• Is AppSubscription created
• Are uplink.enabled and uplink.telemetry.enabled turned on
• Is topic rendered as empty (Template variable missing)

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3. Queue Full

Meaning:

• The plugin has an internal bounded outbound queue (to move I/O out of hot path), which may reject sending when Kafka I/O or delivery receipt piles up.

Suggestion:

• Prioritize checking platform side consumption and broker load (Congestion/Throttling)
• Split App (Separate telemetry and control plane)
• Adjust producer batch/linger (Reduce sending pressure or improve throughput)

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4. Downlink Not Working

Check sequence:

1. Is downlink enabled
2. Is topic exact match (No template/No wildcard)
3. Is payload correct EnvelopeJson/MappedJson
4. Is ackPolicy/failurePolicy as expected (Dropped/Ignored)