Tag: java

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Java release schedule summary: 6 monthly and LTS releases

I have to admit I can never remember which Java releases are the LTS releases at this point, so for reference, here’s a summary:

  • Java 8, the last Oracle release before the 6 month release cadence started, was released March 2014
  • After Java 8, the 6 month release cadence has so far had releases every March and September
  • The 6 month releases are superseded and no longer supported as soon as the next release comes out
  • Between 8 and 11, Java 9 and 10 were non-LTS
  • Java 11 was the first LTS release after Java 8, released on September 2018
  • The LTS releases are on an approx 3 year cycle
  • The next LTS release will be Java 17, expected approx. September 2021

This info was summarized from Oracle’s Java SE support roadmap here and the Wikipedia page here.

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Kafka producer: ip addresses and host names

Scenario:

  • Kafka client 2.4.0
  • Java 1.8.0_151
  • Kafka cluster is running on a machine with hostname ‘ubuntu-confluent’
  • Producer has bootstrap.servers=10.0.0.x (ip of same host as ubuntu-confluent)
  • At runtime, it appears hosthame is passed back to client
  • Subsequent network calls from client back to cluster appear to use hostname instead of ip, and it fails

Exception on client:

2020-03-08 21:26:06,144 [kafka-producer-network-thread | producer-1] WARN org.apache.kafka.clients.NetworkClient [] - [Producer clientId=producer-1] Error connecting to node ubuntu-confluent:9092 (id: 0 rack: null)
java.net.UnknownHostException: ubuntu-confluent: nodename nor servname provided, or not known
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method) ~[?:1.8.0_151]
at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:928) ~[?:1.8.0_151]
at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1323) ~[?:1.8.0_151]
at java.net.InetAddress.getAllByName0(InetAddress.java:1276) ~[?:1.8.0_151]
at java.net.InetAddress.getAllByName(InetAddress.java:1192) ~[?:1.8.0_151]
at java.net.InetAddress.getAllByName(InetAddress.java:1126) ~[?:1.8.0_151]
at org.apache.kafka.clients.ClientUtils.resolve(ClientUtils.java:104) ~[kafka-clients-2.4.0.jar:?]

Easiest fix is to just add an entry to /etc/hosts.

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