Merge pull request #82 from egueli/error_page

Error page
interactionresearchstudio · May 25, 2021 · c168da4 · c168da4
2 parents 7bf5b0a + 2f8bb37
commit c168da4
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Showing 2 changed files with 41 additions and 4 deletions.
diff --git a/naturewatch_camera_server/__init__.py b/naturewatch_camera_server/__init__.py
@@ -83,3 +83,16 @@ def create_app():
 
     flask_app.logger.debug("Initialisation finished")
     return flask_app
+
+def create_error_app(e):
+    """
+    Create flask app about an error occurred in the main app
+    :return: Flask app object
+    """
+    flask_app = Flask(__name__, static_folder="static/client/build")
+
+    @flask_app.route('/')
+    def index():
+        return f"<html><body><h1>Unable to start NaturewatchCameraServer.</h1>An error occurred:<pre>{e}</pre></body></html>"
+
+    return flask_app
diff --git a/naturewatch_camera_server/__main__.py b/naturewatch_camera_server/__main__.py
@@ -1,13 +1,37 @@
-from naturewatch_camera_server import create_app
+from naturewatch_camera_server import create_app, create_error_app
+from picamera.exc import PiCameraError
 import argparse
+import subprocess
 
 parser = argparse.ArgumentParser(description='Launch My Naturewatch Camera')
 parser.add_argument('-p', action='store', dest='port', default=5000,
                     help='Port number to attach to')
 args = parser.parse_args()
 
+class CameraNotFoundException(Exception):
+    pass
+
+def is_camera_enabled():
+    # inspired by https://stackoverflow.com/questions/58250817/raspberry-pi-camera-module-check-if-connected#comment102874971_58250817
+    vcgencmd_result = subprocess.run(['/opt/vc/bin/vcgencmd', 'get_camera'], stdout=subprocess.PIPE)
+    result_text = vcgencmd_result.stdout.decode('utf-8').strip()
+    properties = dict(pair.split('=') for pair in result_text.split(' '))
+    return properties['supported'] == '1'
+
 if __name__ == '__main__':
-    app = create_app()
-    app.camera_controller.start()
-    app.change_detector.start()
+    try:
+        app = create_app()
+        app.camera_controller.start()
+        app.change_detector.start()
+    except Exception as e:
+        if isinstance(e, PiCameraError) and "Camera is not enabled" in str(e):
+            # This error message appears even if the camera _is_ enabled, but the camera is not found.
+            # e.g. due to a connection problem.
+            # We don't want to mislead users into messing with raspi-config, so check if the
+            # camera interface is really disabled.
+            if (is_camera_enabled()):
+                e = CameraNotFoundException("Unable to access camera. Is the cable properly connected?")
+
+        app = create_error_app(e)
+
     app.run(debug=False, threaded=True, port=args.port, host='0.0.0.0')