better error handling + log access to stderr

src/mtl/run_gunicorn.py

@@ -19,6 +19,7 @@ def run_gunicorn():
     options = {
         "bind": "127.0.0.1:15478",
         "workers": 12,
+        "accesslog": "/dev/stderr",
     }
 
     StandaloneApplication(app, options).run()

src/mtl/run_server.py

@@ -16,10 +16,16 @@ def check_property():
         res.headers['Access-Control-Allow-Origin'] = '*'
         res.content_type = "application/json"
         return res
-    traces = data.get("traces")
-    processed_traces = {}
-    for trace_name, trace in traces.items():
-        processed_traces[trace_name] = [(simtime, value) for [simtime, value] in trace]
+    try:
+        traces = data.get("traces")
+        processed_traces = {}
+        for trace_name, trace in traces.items():
+            processed_traces[trace_name] = [(simtime, value) for [simtime, value] in trace]
+    except Exception as e:
+        res = make_response(jsonify("property successfully parsed, but error pre-processing trace. likely your request is not in the expected format. error was: " + str(e)))
+        res.headers['Access-Control-Allow-Origin'] = '*'
+        res.content_type = "application/json"
+        return res
     try:
         result = phi(processed_traces, time=None, quantitative=False)
     except Exception as e: