librd prefers ipv6

[Vitalii Kolmakov (drozel)]

Sometimes, librd v. 1.8.2 tries to reach out the broker and uses the ipv6 which leads to fail
2022-07-14T11:14:21.178Z 002W kafka/librdbase.cpp: 552 01 librd: FAIL, [thrd:hostname2w2.w2:9093/bootstrap]: hostname2w2.w2:9093/bootstrap: Connect to ipv6#[2a03:1e82:a:512::1:3d]:9093 failed: Connection refused 2022-07-14T11:14:21.178Z 002W kafka/librdbase.cpp: 644 01 librd error received: Local: Broker transport failure 2022-07-14T11:14:22.178Z 002W kafka/librdbase.cpp: 552 01 librd: FAIL, [thrd:hostname3w2.w2:9093/bootstrap]: hostname3w2.w2:9093/bootstrap: Connect to ipv6#[2a03:1e82:a:512::1:4c]:9093 failed: Connection refused 2022-07-14T11:14:22.178Z 002W kafka/librdbase.cpp: 644 01 librd error received: Local: Broker transport failure 2022-07-14T11:14:23.178Z 002W kafka/librdbase.cpp: 552 01 librd: FAIL, [thrd:hostname1w2.w2:9093/bootstrap]: hostname1w2.w2:9093/bootstrap: Connect to ipv6#[2a03:1e82:a:512::1:4e]:9093 failed: Connection refused 2022-07-14T11:14:23.178Z 002W kafka/librdbase.cpp: 644 01 librd error received: Local: Broker transport failure 2022-07-14T11:14:23.178Z 002W kafka/librdbase.cpp: 644 01 librd error received: Local: All broker connections are down 2022-07-14T11:14:24.178Z 002W kafka/librdbase.cpp: 552 01 librd: FAIL, [thrd:hostname2w2.w2:9093/bootstrap]: hostname2w2.w2:9093/bootstrap: Connect to ipv6#[2a03:1e82:a:512::1:3d]:9093 failed: Connection refused 2022-07-14T11:14:24.178Z 002W kafka/librdbase.cpp: 644 01 librd error received: Local: Broker transport failure 2022-07-14T11:14:25.178Z 002W kafka/librdbase.cpp: 552 01 librd: FAIL, [thrd:hostname1w2.w2:9093/bootstrap]: hostname1w2.w2:9093/bootstrap: Connect to ipv6#[2a03:1e82:a:512::1:4e]:9093 failed: Connection refused 2022-07-14T11:14:25.178Z 002W kafka/librdbase.cpp: 644 01 librd error received: Local: Broker transport failure

Kafka is started with preferV4:
 ps -aux | fgrep kafka  0  19665  379 20.5 33584708 6617148 ?    Sl   Jul13 4371:30 java --library-path /global/apps/zulu11.54.25-ca-jre11.0.14.1/.run/lib /global/apps/zulu11.54.25-ca-jre11.0.14.1/.run/bin/.java -Xmx6G -Xms6G -XX:G1HeapRegionSize=16M -XX:MinMetaspaceFreeRatio=50 -XX:MaxMetaspaceFreeRatio=80 -Djava.net.preferIPv4Stack=true -server -XX:+UseG1GC -XX:MaxGCPauseMillis=20 -XX:InitiatingHeapOccupancyPercent=35 -XX:+ExplicitGCInvokesConcurrent -XX:MaxInlineLevel=15 -Djava.awt.headless=true -XX:+IgnoreUnrecognizedVMOptions -XX:-UsePerfData -Xlog:gc*:file=/dev/shm/kafka-gc.log:tags,time,uptime,level:filecount=10,filesize=100M -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dkafka.logs.dir=/global/apps/confluent/bin/../logs -Dlog4j.configuration=file:../data/log4j.properties -Dkafka.logs.dir=../data/logs/kafka -cp /global/apps/confluent/bin/../share/java/kafka/*:/global/apps/confluent/bin/../share/java/confluent-telemetry/* -javaagent:../telegraf/jolokia-jvm-1.6.2-agent.jar=port=18778,host=0.0.0.0 kafka.Kafka ../data/kafka.properties

Can I somehow force librd to use ipv4 adresses?

[Druggo Yang (druggo)]

try setting the broker.address.family to v4:
https://github.com/confluentinc/librdkafka/blob/v1.8.2/CONFIGURATION.md?plain=1#L31