[SAMZA-935] hello-samza add kafka wait for dependent services

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 0.10.1
• Component/s: hello-samza
• Labels: newbie
• Assignee: Vishal Kuo
• Reporter: Vishal Kuo
• Created: 15/Apr/16 02:46
• Updated: 23/Apr/16 21:34
• Resolved: 23/Apr/16 19:57

Description

When working with a modified bin/grid script found in https://github.com/theduderog/hello-samza-confluent we found that attempting to start confluent's schemaregistry service immediately after starting the other services resulted in failure since schemaregistry is dependent on kafka which takes a couple seconds to start up.

Would it make sense to add a wait option for kafka like we have added here: https://github.com/theduderog/hello-samza-confluent/blob/master/bin/grid#L118-L132 ?

wait_kafka() {
  echo "Waiting for kafka broker to start..."
  until $(nc -w 2 localhost 9092); do
    printf '.'
    sleep 1
  done
  printf '\n'
  echo "Kafka broker is listening";
}

This way, dependent services started right after ./bin/grid bootsrap won't fail intermittently.

I don't mind adding this if it can be considered useful.