fix segfault in draw_plot_png_bytes

capsulflask/metrics.py

@@ -3,8 +3,9 @@ import matplotlib.pyplot as pyplot
 import matplotlib.dates as mdates
 from functools import reduce 
 import requests
-#import json
+import json
 from datetime import datetime
+from threading import Lock
 from io import BytesIO
 from flask import Blueprint
 from flask import current_app
@@ -15,6 +16,7 @@ from werkzeug.exceptions import abort
 from capsulflask.db import get_model
 from capsulflask.auth import account_required
 
+mutex = Lock()
 bp = Blueprint("metrics", __name__, url_prefix="/metrics")
 
 durations = dict(
@@ -116,6 +118,7 @@ def get_plot_bytes(metric, capsulid, duration, size):
     return (502, None)
 
   series = prometheus_response.json()["data"]["result"]
+  
   if len(series) == 0:
     now_timestamp = datetime.timestamp(datetime.now())
     series = [
@@ -129,13 +132,19 @@ def get_plot_bytes(metric, capsulid, duration, size):
     series[0]["values"]
   ))
 
-  plot_bytes = draw_plot_png_bytes(time_series_data, scale=scales[metric], size_x=sizes[size][0], size_y=sizes[size][1])
+  mutex.acquire()
+  try:
+    plot_bytes = draw_plot_png_bytes(time_series_data, scale=scales[metric], size_x=sizes[size][0], size_y=sizes[size][1])
+  finally:
+    mutex.release()
 
   return (200, plot_bytes)
 
 
 def draw_plot_png_bytes(data, scale, size_x=3, size_y=1):
 
+  #current_app.logger.info(json.dumps(data, indent=4, default=str))
+
   pyplot.style.use("seaborn-dark")
   fig, my_plot = pyplot.subplots(figsize=(size_x, size_y))