Handling cache with ETag and If-None-Match headers.

plugin-server.py

@@ -13,8 +13,8 @@ then $LOCATION$ gets the value of http://example.com/myplugin
 import sys
 import os.path
 import mimetypes
-import hashlib
-from base64 import b64encode
+import string
+import random
 
 import redis
 from flask import Flask, Response, request
@@ -56,6 +56,10 @@ def check_cache(full_path):
     return status
 
 
+def generate_etag(N=12):
+    return ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(N))
+
+
 @app.route("/<plugin>/<path:path>")
 def plugin_file(plugin, path):
     full_path = "{}/{}".format(plugin, path)
@@ -83,11 +87,11 @@ def plugin_file(plugin, path):
 
     resp = Response(result, mimetype=mt)
     resp.headers.add('Access-Control-Allow-Origin', '*')
+    resp.headers.add('ETag', generate_etag())
     resp.status_code = status_code
 
     # return everything if cached response is not allowed
-    if 'Cache-Control' in request.headers:
-        if request.headers['Cache-Control'] in ('no-cache', 'max-age=0'):
+    if 'If-None-Match' not in request.headers:
         resp.status_code = 200
 
     return resp