add a simple pipeline unit test without mara db

mara_pipelines/execution.py

@@ -53,6 +53,13 @@ def run_pipeline(pipeline: pipelines.Pipeline, nodes: {pipelines.Node} = None,
     # A queue for receiving events from forked sub processes
     event_queue = multiprocessing_context.Queue()
 
+    # The historical node cost is taken from the 'mara' db. If the 'mara' datatabase is not defined
+    # (e.g. in testing scenarios) we do not use the node cost.
+    import mara_db.config
+    use_historical_node_cost = 'mara' in mara_db.config.databases()
+    if not use_historical_node_cost:
+        print(f"[WARNING] The 'mara' database is not defined. The historical node costs are not used, the execution path might be inefficient.", file=sys.stderr)
+
     # The function that is run in a sub process
     def run():
 
@@ -64,7 +71,7 @@ def run():
             node_queue: [pipelines.Node] = []
 
             # data needed for computing cost
-            node_durations_and_run_times = node_cost.node_durations_and_run_times(pipeline)
+            node_durations_and_run_times = node_cost.node_durations_and_run_times(pipeline) if use_historical_node_cost else {}
 
             # Putting nodes into the node queue
             def queue(nodes: [pipelines.Node]):
@@ -207,7 +214,8 @@ def track_finished_pipelines():
                                         next_node.add_dependency(pipeline_node, downstream)
 
                             # get cost information for children
-                            node_durations_and_run_times.update(node_cost.node_durations_and_run_times(next_node))
+                            if use_historical_node_cost:
+                                node_durations_and_run_times.update(node_cost.node_durations_and_run_times(next_node))
 
                             # queue all child nodes
                             queue(list(next_node.nodes.values()))
@@ -314,7 +322,11 @@ def track_finished_pipelines():
     run_process = multiprocessing_context.Process(target=run, name='pipeline-' + '-'.join(pipeline.path()))
     run_process.start()
 
-    runlogger = run_log.RunLogger()
+    if 'mara' in mara_db.config.databases():
+        runlogger = run_log.RunLogger()
+    else:
+        runlogger = run_log.NullLogger()
+        print(f"[WARNING] The events of the pipeline execution are not saved in a db", file=sys.stderr)
 
     # make sure that we close this run (if still open) as failed when we close this python process
     # On SIGKILL we will still leave behind open runs...

mara_pipelines/logging/run_log.py

@@ -1,10 +1,8 @@
 """Logging pipeline runs, node output and status information in mara database"""
 
-import psycopg2.extensions
 import sqlalchemy.orm
 from sqlalchemy.ext.declarative import declarative_base
 
-import mara_db.postgresql
 from .. import config
 from ..logging import pipeline_events, system_statistics
 from .. import events
@@ -73,6 +71,15 @@ def close_open_run_after_error(run_id: int):
     """Closes all open run and node_run for this run_id as failed"""
     if run_id is None:
         return
+
+    import mara_db.config
+
+    if 'mara' not in mara_db.config.databases():
+        return
+
+    import psycopg2.extensions
+    import mara_db.postgresql
+
     _close_run = f'''
 UPDATE  data_integration_run
 SET end_time = now(), succeeded = FALSE
@@ -98,11 +105,22 @@ def close_open_run_after_error(run_id: int):
             print(f'Cleaned up open runs/node_runs (run_id = {run_id})')
 
 
+class NullLogger(events.EventHandler):
+    """A run logger not handling events"""
+    run_id: int = None
+
+    def handle_event(self, event: events.Event):
+        pass
+
+
 class RunLogger(events.EventHandler):
+    """A run logger saving the pipeline events to the 'mara' database alias"""
     run_id: int = None
     node_output: {tuple: [pipeline_events.Output]} = None
 
     def handle_event(self, event: events.Event):
+        import psycopg2.extensions
+        import mara_db.postgresql
 
         if isinstance(event, pipeline_events.RunStarted):
             with mara_db.postgresql.postgres_cursor_context('mara') as cursor:  # type: psycopg2.extensions.cursor

setup.py

@@ -28,6 +28,12 @@ def get_long_description():
         'requests>=2.19.1'
     ],
 
+    extras_require={
+        'test': [
+            'pytest',
+            'mara_app>=1.5.2'],
+    },
+
     setup_requires=['setuptools_scm'],
     include_package_data=True,
 

tests/test_execute_pipeline.py

@@ -0,0 +1,26 @@
+import pytest
+
+from mara_app.monkey_patch import patch
+
+import mara_db.config
+patch(mara_db.config.databases)(lambda: {})
+
+
+def test_execute_without_db():
+    from mara_pipelines.commands.python import RunFunction
+    from mara_pipelines.pipelines import Pipeline, Task
+    from mara_pipelines.ui.cli import run_pipeline
+
+    pipeline = Pipeline(
+        id='test_execute_without_db',
+        description="Tests if a pipeline can be executed without database")
+
+    def command_function() -> bool:
+        return True
+
+    pipeline.add(
+        Task(id='run_python_function',
+             description="Runs a sample python function",
+             commands=[RunFunction(function=command_function)]))
+
+    assert run_pipeline(pipeline)