AssertionError: INTERNAL: No default project is specified - python-2.7

Question

New to airflow. Trying to run the sql and store the result in a BigQuery table.
Getting following error. Not sure where to setup the default_rpoject_id.
Please help me.
Error:
Traceback (most recent call last):
File "/usr/local/bin/airflow", line 28, in <module>
args.func(args)
File "/usr/local/lib/python2.7/dist-packages/airflow/bin/cli.py", line 585, in test
ti.run(ignore_task_deps=True, ignore_ti_state=True, test_mode=True)
File "/usr/local/lib/python2.7/dist-packages/airflow/utils/db.py", line 53, in wrapper
result = func(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/airflow/models.py", line 1374, in run
result = task_copy.execute(context=context)
File "/usr/local/lib/python2.7/dist-packages/airflow/contrib/operators/bigquery_operator.py", line 82, in execute
self.allow_large_results, self.udf_config, self.use_legacy_sql)
File "/usr/local/lib/python2.7/dist-packages/airflow/contrib/hooks/bigquery_hook.py", line 228, in run_query
default_project_id=self.project_id)
File "/usr/local/lib/python2.7/dist-packages/airflow/contrib/hooks/bigquery_hook.py", line 917, in _split_tablename
assert default_project_id is not None, "INTERNAL: No default project is specified"
AssertionError: INTERNAL: No default project is specified
Code:
sql_bigquery = BigQueryOperator(
task_id='sql_bigquery',
use_legacy_sql=False,
write_disposition='WRITE_TRUNCATE',
allow_large_results=True,
bql='''
#standardSQL
SELECT ID, Name, Group, Mark, RATIO_TO_REPORT(Mark) OVER(PARTITION BY Group) AS percent FROM `tensile-site-168620.temp.marks`
''',
destination_dataset_table='temp.percentage',
dag=dag
)

Answer 1

EDIT: I finally fixed this problem by simply adding the bigquery_conn_id='bigquery' parameter in the BigQueryOperator task, after running the code below in a separate python script.
Apparently you need to specify your project ID in Admin -> Connection in the Airflow UI. You must do this as a JSON object such as "project" : "".
Personally I can't get the webserver working on GCP so this is unfeasible. There is a programmatic solution here:
from airflow.models import Connection
from airflow.settings import Session
session = Session()
gcp_conn = Connection(
conn_id='bigquery',
conn_type='google_cloud_platform',
extra='{"extra__google_cloud_platform__project":"<YOUR PROJECT HERE>"}')
if not session.query(Connection).filter(
Connection.conn_id == gcp_conn.conn_id).first():
session.add(gcp_conn)
session.commit()
These suggestions are from a similar question here.

Answer 2

I get the same error when running airflow locally. My solution is to add a the following connection string as a environment variable:
AIRFLOW_CONN_BIGQUERY_DEFAULT="google-cloud-platform://?extra__google_cloud_platform__project=<YOUR PROJECT HERE>"
BigQueryOperator uses the "bigquery_default" connection. When not specified, local airflow uses an internal version of the connection which misses the property project_id. As you can see the connection string above provides the project_id property.
On startup Airflow loads environment variables that start with "AIRFLOW_" into memory. This mechanism can be used to override airflow properties and providing connections when running locally, as explained in the airflow documentation here. Note this also works when running airflow directly without starting the web server.
So I have set up environments variables for all my connections, for example AIRFLOW_CONN_MYSQL_DEFAULT. I have put them into a .ENV file that get sourced from my IDE, but putting them into your .bash_profile would work fine too.
When you look inside your airflow instance on Cloud Composer, you see that the at the "bigquery_default" connection there has the project_idproperty set. That's why BigQueryOperator works when running through Cloud Composer.
(I am on airflow 1.10.2 and BigQuery 1.10.2)