Slight refactoring

- Use Flask Blueprint for configuring service component
- Handle data generator registration within different file

Author: amotl

README.rst

@@ -6,8 +6,12 @@ Grafana Pandas Datasource
 *****
 About
 *****
-A Python-native Grafana datasource using Pandas for timeseries and table data.
-Inspired by and compatible with the simple json datasource.
+A REST API based on Flask for serving Pandas Dataframes to Grafana.
+
+This way, a native Python application can be used to directly supply
+data to Grafana both easily and powerfully.
+
+It was inspired by and is compatible with the simple json datasource.
 
 https://gist.github.com/linar-jether/95ff412f9d19fdf5e51293eb0c09b850
 

examples/sinewave-midnights/demo.py

@@ -1,16 +1,40 @@
+"""
+Copyright 2017 Linar <[email protected]>
+Copyright 2020 Andreas Motl <[email protected]>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+import pandas as pd
+import numpy as np
+from grafana_pandas_datasource import create_app
+from grafana_pandas_datasource.registry import data_generators as dg
+from grafana_pandas_datasource.service import pandas_component
+
 """
 Demo for grafana-pandas-datasource.
 
+This is a demo program which generates data using NumPy and Pandas.
+It creates
+- a sine wave for data and
+- midnight times for annotations
+
 To query the reader, use ``<reader_name>:<query_string>``, e.g.
 - ``sine_wave:24``
 - ``midnights:xx``
 """
-import pandas as pd
-import numpy as np
-from grafana_pandas_datasource.service import get_application, add_reader, add_annotation_reader
 
 
-def main():
+def define_and_register_data():
 
     # Sample timeseries reader.
     def get_sine(freq, ts_range):
@@ -22,12 +46,23 @@ def get_sine(freq, ts_range):
     def get_midnights(query_string, ts_range):
         return pd.Series(index=pd.date_range(ts_range['$gt'], ts_range['$lte'], freq='D', normalize=True), dtype='float64').fillna('Text for annotation - midnight')
 
-    # Register data generation functions.
-    add_reader('sine_wave', get_sine)
-    add_annotation_reader('midnights', get_midnights)
+    # Register data generators.
+    dg.add_metric_reader("sine_wave", get_sine)
+    dg.add_annotation_reader("midnights", get_midnights)
+
+
+def main():
+
+    # Define and register data generators.
+    define_and_register_data()
+
+    # Create Flask application.
+    app = create_app()
+
+    # Register Pandas component.
+    app.register_blueprint(pandas_component, url_prefix="/")
 
-    # Get Flask application and invoke it.
-    app = get_application()
+    # Invoke Flask application.
     app.run(host='127.0.0.1', port=3003, debug=True)
 
 

grafana_pandas_datasource/__init__.py

@@ -0,0 +1,40 @@
+"""
+Copyright 2017 Linar <[email protected]>
+Copyright 2020 Andreas Motl <[email protected]>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+from flask import Flask
+from flask_cors import CORS
+
+
+def create_app(test_config=None) -> Flask:
+    """
+    Create and configure the Flask application, with CORS.
+
+    - https://flask.palletsprojects.com/en/1.1.x/tutorial/factory/
+    - https://flask-cors.readthedocs.io/
+
+    :param test_config:
+    :return: Configured Flask application.
+    """
+
+    # Create Flask application.
+    app = Flask(__name__)
+
+    # Initialize Cross Origin Resource sharing support for
+    # the application on all routes, for all origins and methods.
+    CORS(app)
+    app.config['CORS_HEADERS'] = 'Content-Type'
+
+    return app

grafana_pandas_datasource/registry.py

@@ -0,0 +1,54 @@
+"""
+Copyright 2017 Linar <[email protected]>
+Copyright 2020 Andreas Motl <[email protected]>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+from typing import Dict, Callable
+from dataclasses import dataclass, field
+
+
+@dataclass
+class DataGenerators:
+    """
+    Store references to data generator functions
+    yielding Pandas data frames.
+    """
+
+    metric_readers: Dict[str, Callable] = field(default_factory=dict)
+    metric_finders: Dict[str, Callable] = field(default_factory=dict)
+    annotation_readers: Dict[str, Callable] = field(default_factory=dict)
+    panel_readers: Dict[str, Callable] = field(default_factory=dict)
+
+    def add_metric_reader(self, name, reader):
+        self.metric_readers[name] = reader
+
+    def add_metric_finder(self, name, finder):
+        self.metric_finders[name] = finder
+
+    def add_annotation_reader(self, name, reader):
+        self.annotation_readers[name] = reader
+
+    def add_panel_reader(self, name, reader):
+        self.panel_readers[name] = reader
+
+
+"""
+@dataclass
+class DataGeneratorRegistry:
+    generators: Dict[str, DataGenerators] = field(default_factory=dict)
+"""
+
+
+# Global reference to instance of DataGenerators.
+data_generators: DataGenerators = DataGenerators()

grafana_pandas_datasource/service.py

@@ -1,13 +1,6 @@
 """
-A REST API based on Flask for serving Pandas Dataframes to Grafana.
-
-The idea is to use ``flask_restful`` and create a Blueprint to be
-used by a parent project (i.e. a larger API project where ``/grafana/``
-endpoints are used by Grafana's SimpleJson plugin).
-
-----
-
 Copyright 2017 Linar <[email protected]>
+Copyright 2020 Andreas Motl <[email protected]>
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -21,50 +14,25 @@
 See the License for the specific language governing permissions and
 limitations under the License.
 """
-from flask import Flask, request, jsonify, abort
-from flask_cors import CORS, cross_origin
+from flask import Blueprint, request, jsonify, abort
+from flask_cors import cross_origin
 import pandas as pd
 
+from grafana_pandas_datasource.registry import data_generators as dg
 from grafana_pandas_datasource.util import dataframe_to_response, dataframe_to_json_table, annotations_to_response
 
-
-app = Flask(__name__)
-
-cors = CORS(app)
-app.config['CORS_HEADERS'] = 'Content-Type'
-
+pandas_component = Blueprint('pandas-component', __name__)
 methods = ('GET', 'POST')
 
-metric_finders = {}
-metric_readers = {}
-annotation_readers = {}
-panel_readers = {}
-
-
-def add_reader(name, reader):
-    metric_readers[name] = reader
-
 
-def add_finder(name, finder):
-    metric_finders[name] = finder
-
-
-def add_annotation_reader(name, reader):
-    annotation_readers[name] = reader
-
-
-def add_panel_reader(name, reader):
-    panel_readers[name] = reader
-
-
-@app.route('/', methods=methods)
+@pandas_component.route('/', methods=methods)
 @cross_origin()
 def hello_world():
     print(request.headers, request.get_json())
     return 'Jether\'s Grafana Pandas Datasource, used for rendering HTML panels and timeseries data.'
 
 
-@app.route('/search', methods=methods)
+@pandas_component.route('/search', methods=methods)
 @cross_origin()
 def find_metrics():
     print(request.headers, request.get_json())
@@ -77,19 +45,20 @@ def find_metrics():
     else:
         finder = target
 
-    if not target or finder not in metric_finders:
+    if not target or finder not in dg.metric_finders:
         metrics = []
         if target == '*':
-            metrics += metric_finders.keys() + metric_readers.keys()
+            metrics += dg.metric_finders.keys()
+            metrics += dg.metric_readers.keys()
         else:
             metrics.append(target)
 
         return jsonify(metrics)
     else:
-        return jsonify(list(metric_finders[finder](target)))
+        return jsonify(list(dg.metric_finders[finder](target)))
 
 
-@app.route('/query', methods=methods)
+@pandas_component.route('/query', methods=methods)
 @cross_origin(max_age=600)
 def query_metrics():
     print(request.headers, request.get_json())
@@ -112,7 +81,7 @@ def query_metrics():
         req_type = target.get('type', 'timeserie')
 
         finder, target = target['target'].split(':', 1)
-        query_results = metric_readers[finder](target, ts_range)
+        query_results = dg.metric_readers[finder](target, ts_range)
 
         if req_type == 'table':
             results.extend(dataframe_to_json_table(target, query_results))
@@ -122,7 +91,7 @@ def query_metrics():
     return jsonify(results)
 
 
-@app.route('/annotations', methods=methods)
+@pandas_component.route('/annotations', methods=methods)
 @cross_origin(max_age=600)
 def query_annotations():
     print(request.headers, request.get_json())
@@ -139,12 +108,12 @@ def query_annotations():
         abort(404, Exception('Target must be of type: <finder>:<metric_query>, got instead: ' + query))
 
     finder, target = query.split(':', 1)
-    results.extend(annotations_to_response(query, annotation_readers[finder](target, ts_range)))
+    results.extend(annotations_to_response(query, dg.annotation_readers[finder](target, ts_range)))
 
     return jsonify(results)
 
 
-@app.route('/panels', methods=methods)
+@pandas_component.route('/panels', methods=methods)
 @cross_origin()
 def get_panel():
     print(request.headers, request.get_json())
@@ -159,8 +128,4 @@ def get_panel():
         abort(404, Exception('Target must be of type: <finder>:<metric_query>, got instead: ' + query))
 
     finder, target = query.split(':', 1)
-    return panel_readers[finder](target, ts_range)
-
-
-def get_application():
-    return app
+    return dg.panel_readers[finder](target, ts_range)