title: Getting unique_id for apache airflow tasks
body: <p>I am new to airflow .In my company for ETL pipeline currently we are using Crontab and custom Scheduler(developed in-house) .Now we are planning to implement apache airflow for our all Data Pipe-line scenarios .For that while exploring the features not able to find <strong>unique_id</strong> for each Task Instances/Dag .When I searched most of the solutions ended up in macros and template .But none of them are not providing a uniqueID for a task .But I am able to see incremental uniqueID in the UI for each tasks .Is there any way to easily access those variables inside my python method .The main use case is I need to pass those ID's as a parameter to out Python/ruby/Pentaho jobs which is called as scripts/Methods .</p>
  
  <p>For Example </p>
  
  <p>my shell script 'test.sh ' need two arguments one is run_id and other is collection_id. Currently we are generating this unique run_id from a centralised Database and passing it to the jobs .If it is already present in the airflow context we are going to use that</p>
  
  <pre><code>from airflow.operators.bash_operator import BashOperator
  from datetime import date, datetime, timedelta
  from airflow import DAG
  
  shell_command =  "/data2/test.sh -r run_id -c collection_id"
  
  
  putfiles_s3 = BashOperator(
                  task_id='putfiles_s3',
                  bash_command=shell_command,
                  dag=dag)
  </code></pre>
  
  <p>Looking for a unique run_id(Either Dag level/task level) for each run while  executing this Dag(scheduled/manual) </p>
  
  <p>Note: This is a sample task .There will be multiple dependant  task to this Dag .
  Attaching Job_Id screenshot from airflow UI
  <a href="https://i.stack.imgur.com/fEIN5.png" rel="noreferrer"><img src="https://i.stack.imgur.com/fEIN5.png" alt="enter image description here"></a></p>
  
  <p>Thanks
  Anoop R</p>