Airflow BashOperator Parameter From XCom Value - airflow

Question

I am having some problem assigning an xcom value to the BashOperator.
All the parameters are properly retrieved except the tmp_dir, which is an xcom value generated during init_dag. I was able to retrieve the value in my custom operator but not being able to do it in the BashOperator. I have added the outputs of the three different ways I have tried that came to my mind.
I think one way could be if I could store that value in a variable but I was also not able to figure it out how.
Any help will be highly appreciated.
Here is my DAG code:
import airflow
from airflow.models import DAG
from airflow.utils.dates import days_ago
from airflow.models import Variable
from utility import util
import os
from airflow.operators.bash_operator import BashOperator
from operators.mmm_operator import MMMOperator #it is a custom operator
from operators.iftp_operator import IFTPOperator #it is another custom operator
AF_DATAMONTH = util.get_date_by_format(deltaMth=2,deltaDay=0,ft='%b_%Y').lower() #it gives a date in required format
AF_FILENM_1 = 'SOME_FILE_' + AF_DATAMONTH + '.zip' #required filename for ftp
default_args = {
'owner': 'airflow',
'depends_on_past': False,
'start_date': days_ago(0),
}
dag = DAG(dag_id='my_dag', default_args=default_args, schedule_interval=None)
init_dag = MMMOperator(
task_id='init_dag',
provide_context=True,
mmm_oracle_conn_id=Variable.get('SOME_VARIABLE'),
mmm_view="{0}.{1}".format(Variable.get('ANOTHER_VARIABLE'), AF_DAG_MMM_VIEW_NM),
mmm_view_filter=None,
mmm_kv_type=True,
mmm_af_env_view="{0}.{1}".format(Variable.get('ANOTHER_VARIABLE_1'),Variable.get('ANOTHER_VARIABLE_2')),
dag=dag
) #local_tmp_folder is generated here and pushed via xcom
download_ftp_files = IFTPOperator(task_id='download_ftp_files',
ftp_conn_id=util.getFromConfig("nt_conn_id"), #value properly retrieved by xcom_pull
operation='GET',
source_path=util.getFromConfig("nt_remote_folder"), #value properly retrieved by xcom_pull
dest_path=util.getFromConfig("local_tmp_folder"), #value properly retrieved by xcom_pull
filenames=AF_FILENM,
dag=dag
)
bash_cmd_template = "cd /vagrant/ && python3 hello_print.py {{params.client}} {{params.task}} {{params.environment}} {{params.tmp_dir}} {{params.af_file_nm}}"
#try 1 output value for params.tmp_dir: {{ ti.xcom_pull(task_ids="init_dag")["local_tmp_folder"] }} - instead of the actual tmp folder location
#try 2 and try 3 output: Broken DAG: [/home/vagrant/airflow/dags/my_dag.py] name 'ti' is not defined - message in UI
execute_main_py_script = BashOperator(
task_id='execute_main_py_script',
bash_command=bash_cmd_template,
params={'client' : 'some_client',
'task' : 'load_some_task',
'environment' : 'environment_name',
#'tmp_dir' : util.getFromConfig("local_tmp_folder"), #try 1
#'tmp_dir' : {{ ti.xcom_pull(task_ids="init_dag")["local_tmp_folder"] }} #try 2
#'tmp_dir' : ti.xcom_pull(task_ids="init_dag")["local_tmp_folder"] #try 3
'af_file_nm' : AF_FILENM_1
},
provide_context=True,
dag=dag
)
init_dag >> download_ftp_files >> execute_main_py_script

Answer 1

The params argument of the BashOperator is not Jinja Templated hence any values you pass in params would be rendered "as-is".
You should directly pass the value of tmp_dir in bash_cmd_template as follows:
bash_cmd_template = """
cd /vagrant/ && python3 hello_print.py {{params.client}} {{params.task}} {{params.environment}} {{ ti.xcom_pull(task_ids="init_dag")["local_tmp_folder"] }} {{params.af_file_nm}}
"""
execute_main_py_script = BashOperator(
task_id='execute_main_py_script',
bash_command=bash_cmd_template,
params={'client' : 'some_client',
'task' : 'load_some_task',
'environment' : 'environment_name',
'af_file_nm' : AF_FILENM_1
},
provide_context=True,
dag=dag
)