1. Connection Failure

• Does serviceUrl protocol and port match (pulsar://6650 / pulsar+ssl://6651)
• Does token have permission (tenant/namespace/topic)
• TLS handshake failure (Certificate chain/hostname)

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2. Connected but No Data

Prioritize checking:

• Does AppSubscription exist
• Is uplink mapping enabled
• Are you consuming on the correct topic (Pulsar topic prefix is easy to write wrong)

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3. Downlink Not Working

Check sequence:

1. downlink enabled
2. Is topic exact match (No template/No wildcard)
3. Does AckPolicy/FailurePolicy cause ack/nack and retry behavior as expected
4. Does MappedJson filter match

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4. Backlog Increasing/Throughput Dropping

• Can consumer keep up (Platform side backlog)
• Need to enable batching (Throughput first)
• Is QueuePolicy reasonable (Telemetry suggest Discard)