Fix timezone issues, update Dockerfile

Dockerfile

@@ -1,16 +1,18 @@
-FROM python:alpine3.9
+FROM python:3-alpine
+
 
 WORKDIR /app/
 
 COPY requirements.txt /app/
-RUN apk add --no-cache --virtual build-deps gcc musl-dev libffi-dev \
-    && pip install -r requirements.txt \
-    && apk del build-deps
+
+RUN apk update && apk add --no-cache --virtual build-deps build-base gcc musl-dev libffi-dev libev-dev
+RUN pip install -r requirements.txt
+RUN apk del build-deps
 
 COPY GrafanaDatastoreServer.py /app/
 
 EXPOSE 8080
 ENV REDIS_HOST=localhost
 ENV REDIS_PORT=6379
 
-CMD /app/GrafanaDatastoreServer.py --redis-server $REDIS_HOST --redis-port $REDIS_PORT
+CMD /app/GrafanaDatastoreServer.py --redis-server $REDIS_HOST --redis-port $REDIS_PORT

GrafanaDatastoreServer.py

@@ -12,8 +12,6 @@
 app = Flask(__name__)
 CORS(app)
 
-EPOCH = datetime(1970, 1, 1, 0, 0, 0)
-
 REDIS_POOL = None
 SCAN_TYPE_SCRIPT = """local cursor, pat, typ, cnt = ARGV[1], ARGV[2], ARGV[3], ARGV[4] or 100
 local rep = {}
@@ -63,11 +61,9 @@ def query():
     request = flask.request.get_json()
     response = []
 
-    # !!! dates 'from' and 'to' are expected to be in UTC, which is what Grafana provides here.
-    # If not in UTC, use pytz to set to UTC timezone and subtract the utcoffset().
-    # Time delta calculations should always be done in UTC to avoid pitfalls of daylight offset changes.
-    stime = (dateutil.parser.parse(request['range']['from']) - EPOCH) / timedelta(milliseconds=1)
-    etime = (dateutil.parser.parse(request['range']['to']) - EPOCH) / timedelta(milliseconds=1)
+    # dates 'from' and 'to' are expected to be in UTC, which is what Grafana provides here.
+    stime = dateutil.parser.parse(request['range']['from']).timestamp() * 1000
+    etime = dateutil.parser.parse(request['range']['to']).timestamp() * 1000
 
     redis_client = redis.Redis(connection_pool=REDIS_POOL)
     targets = process_targets([t['target'] for t in request['targets']], redis_client)

README.md

@@ -51,3 +51,6 @@ optional arguments:
   --redis-port REDIS_PORT
                         redis server port
 ```
+
+#### Note about timezone
+Grafana uses UTC timestamps to query its datastores. This datastore will use the same timestamps to query Redis, which means that it assumes all timestamps are UTC based.