What to do when Airflow BashOperator fails with TemplateNotFound error

This article is a part of my "100 data engineering tutorials in 100 days" challenge. (61/100)

Airflow has an annoying error that causes a failure when we try to use the BashOperator like this:

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operator = BashOperator(
    task_id='operator_id',
    bash_command='some_bash_script.sh',
    dag=dag)

What is wrong? For some reason, it tries to apply the template variables to the “bash_command” parameter even if we don’t use them. Consequently, the template loader fails with the TemplateNotFound error because it cannot find any template variables in the given string.

Of course, in this case, it is the correct behavior because we don’t use any template variables. Unfortunately, it is not the behavior we want.

To make Airflow ignore the missing template and just use the given string as the file name (as it should do anyway), we have to trick the template parsing code by adding a single space at the end of the parameter:

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operator = BashOperator(
    task_id='operator_id',
    bash_command='some_bash_script.sh ',
    dag=dag)

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Bartosz Mikulski

Bartosz Mikulski

  • Data/MLOps engineer by day
  • DevRel/copywriter by night
  • Python and data engineering trainer
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  • Contributed a chapter to the book "97 Things Every Data Engineer Should Know"
  • Twitter: @mikulskibartosz
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