Exporter fails with Sqlite DB used in development environment

[ryan-carlson]

When using the Sqlite DB, the following error occurs when attempting to open the metrics page.

Traceback (most recent call last):
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/flask/app.py", line 1982, in wsgi_app
response = self.full_dispatch_request()
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/flask/app.py", line 1614, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/flask/app.py", line 1517, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/flask/_compat.py", line 33, in reraise
raise value
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/flask/app.py", line 1612, in full_dispatch_request
rv = self.dispatch_request()
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/flask/app.py", line 1598, in dispatch_request
return self.view_functionsrule.endpoint
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/flask_admin/base.py", line 69, in inner
return self._run_view(f, *args, **kwargs)
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/flask_admin/base.py", line 368, in _run_view
return fn(self, *args, **kwargs)
File "/Users/ryan.carlson/airflow/plugins/prometheus_exporter/prometheus_exporter.py", line 164, in index
return Response(generate_latest(), mimetype='text/plain')
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/prometheus_client/exposition.py", line 88, in generate_latest
for metric in registry.collect():
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/prometheus_client/core.py", line 147, in collect
for metric in collector.collect():
File "/Users/ryan.carlson/airflow/plugins/prometheus_exporter/prometheus_exporter.py", line 150, in collect
for dag in get_dag_duration_info():
File "/Users/ryan.carlson/airflow/plugins/prometheus_exporter/prometheus_exporter.py", line 108, in get_dag_duration_info
DagRun.state == State.RUNNING
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 2703, in all
return list(self)
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 90, in instances
util.raise_from_cause(err)
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 203, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb, cause=cause)
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 187, in reraise
raise value
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 78, in instances
for row in fetch]
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 78, in
for row in fetch]
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 77, in
rows = [keyed_tuple([proc(row) for proc in process])
File "/Users/ryan.carlson/.virtualenvs/spothero-dataflows/lib/python3.6/site-packages/sqlalchemy/sql/sqltypes.py", line 1709, in process
value = impl_processor(value)
ValueError: Couldn't parse datetime string '0' - value is not a string.

[ryan-carlson]

I have code fix that I can share which enable support Sqlite. Is it possible for me to submit this as a PR?

[elephantum]

@ryan-carlson of course! We are glad to receive contributions.

[ryan-carlson]

Sounds great, please see #37

[elephantum]

I believe this can be closed, as #37 is merged

[ryan-carlson]

Confirmed, I have tested with the latest master