Example of `attributeWhenReady` in YAML Blueprint

attribute-when-ready-example.yaml

name: "Attribute When Ready Example"
location: <add-location-here>

services: 
  - type: org.apache.brooklyn.entity.software.base.VanillaSoftwareProcess
    id: item-A
    name: A
    
    launch.command: |
      echo $(date)
      echo "A: sleeping for 10 seconds"
      sleep 10
      echo hello | nc -l 4321 &
      echo $! > $PID_FILE
      echo "A: launch.command executed"

    env:                  { CHECK_MARKER: "checkRunning", STOP_MARKER: "stop" }
    checkRunning.command: echo $CHECK_MARKER >> DATE && test -f "$PID_FILE" && ps -p `cat $PID_FILE` >/dev/null
    stop.command:         echo $STOP_MARKER  >> DATE && test -f "$PID_FILE" && { kill -9 `cat $PID_FILE`; rm /tmp/vanilla.pid; }

  - type: org.apache.brooklyn.entity.software.base.VanillaSoftwareProcess
    id: item-B
    name: B
    
    brooklyn.config:
      launch.latch: $brooklyn:component("item-A").attributeWhenReady("service.isUp")
    
    launch.command: |
      echo $(date)
      echo hello | nc -l 4322 &
      echo $! > $PID_FILE
      echo "B: launch.command executed"

    env:                  { CHECK_MARKER: "checkRunning", STOP_MARKER: "stop" }
    checkRunning.command: echo $CHECK_MARKER >> DATE && test -f "$PID_FILE" && ps -p `cat $PID_FILE` >/dev/null
    stop.command:         echo $STOP_MARKER  >> DATE && test -f "$PID_FILE" && { kill -9 `cat $PID_FILE`; rm /tmp/vanilla.pid; }