Offset increased for eof pseudo messages

[gvogel-hh]

Description

When using enable.partition.eof=true, the offset returned by rd_kafka_position() after consuming the artificial eof message is the last real message's offset + 2. This changed at some point between 2.0.2 and 2.2.0.

How to reproduce

Set enable.partition.eof=true, consume an eof message, and call rd_kafka_position().

IMPORTANT: Always try to reproduce the issue on the latest released version (see https://github.com/confluentinc/librdkafka/releases), if it can't be reproduced on the latest version the issue has been fixed.

Checklist

IMPORTANT: We will close issues where the checklist has not been completed.

Please provide the following information:

• librdkafka version (release number or git tag): broken in >= 2.2.0; bug is not present in 2.0.2
• Apache Kafka version: <REPLACE with e.g., 0.10.2.3>
• librdkafka client configuration: <REPLACE with e.g., message.timeout.ms=123, auto.reset.offset=earliest, ..>
• Operating system: <REPLACE with e.g., Centos 5 (x64)>
• Provide logs (with debug=.. as necessary) from librdkafka
• Provide broker log excerpts
• Critical issue