Description

with KIP-896: it's planned that older
RPC versions. When connecting to such broker, librdkafka deactivates most features because the maximum version is almost always the same as the minimum version and corresponds to a version being removed.

How to reproduce

In rd_kafka_broker_set_api_versions can be overridden this way:

        size_t i;
        for (i = 0; i < api_cnt; i++) {
                if (apis[i].ApiKey == RD_KAFKAP_Produce)
                        apis[i].MinVer = 8;
                if (apis[i].ApiKey == RD_KAFKAP_ApiVersion)
                        apis[i].MinVer = 2;
                if (apis[i].ApiKey == RD_KAFKAP_FindCoordinator)
                        apis[i].MinVer = 1;
                if (apis[i].ApiKey == RD_KAFKAP_JoinGroup) {
                        apis[i].MinVer = -2;
                        apis[i].MaxVer = -2;
                }
                if (apis[i].ApiKey == RD_KAFKAP_SaslHandshake)
                        apis[i].MinVer = 2;
                if (apis[i].ApiKey == RD_KAFKAP_InitProducerId)
                        apis[i].MinVer = 1;
                if (apis[i].ApiKey == RD_KAFKAP_ListOffsets)
                        apis[i].MinVer = 1;
        }

It happens that all features are disabled.
test_minver_increased.log

Minimum required MinVer values are currently:

Produce 3
Fetch 4
ApiVersion 0
FindCoordinator 0
OffsetCommit 2
OffsetFetch 1
JoinGroup 0
SyncGroup 0
Heartbeat 0
LeaveGroup 0
SaslHandshake 0
ListOffsets 1
InitProducerId 0
SaslAuthenticate 1

by comparing it to KIP 896 removed versions (non-baseline), all versions described in the KIP can be removed. Removing JoinGroup v0 will disable the broker feature RD_KAFKA_FEATURE_BROKER_BALANCED_CONSUMER that isn't used internally and not exposed in the public API.

Checklist

Please provide the following information:

• librdkafka version (release number or git tag): v1.x+ up to latest
• Apache Kafka version: <REPLACE with e.g., 0.10.2.3>
• librdkafka client configuration: any
• Operating system: any
• Provide logs (with debug=.. as necessary) from librdkafka
• Provide broker log excerpts
• Critical issue