WIP: Implement regular scraping of the calendar sources in the background, instead of blocking in the foreground process

README.md

@@ -92,7 +92,6 @@ Configuration is done through a JSON config file:
     "port": 8090,
     "start_delta": "-PT3H",
     "end_delta": "P30D",
-    "cache": "PT15M",
     "tz": "Europe/Zurich",
     "calendars": {
         "private": {
@@ -104,6 +103,7 @@ Configuration is done through a JSON config file:
             }
         },
         "public": {
+            "interval": "P1D",
             "url": "https://example.cloud/dav/me/public.ics"
         },
         "confidential": {
@@ -136,11 +136,11 @@ Configuration is done through a JSON config file:
 | `port` | int | The port to listen on. |
 | `start_delta` | string | A signed ISO 8601 duration string, describing the event range start offset relative to the current time. |
 | `end_delta` | string | An unsigned ISO 8601 duration string, describing the event range end offset relative to the current time. |
-| `cache` | string | An unsigned ISO 8601 duration string, describing the cache timeout duration. |
 | `tz` | string | The local timezone. |
 | `calendars` | dict | The calendars to scrape. |
 | `keys(calendars)` | string | Name of the calendar. |
 | `calendars.*.url` | string | The HTTP or HTTPS URL to scrape. |
+| `calendars.*.interval` | string | An unsigned ISO 8601 duration string, describing the scrape interval for this calendar. |
 | `calendars.*.ca` | string | Path to the CA certificate file to validate the server's TLS certificate against, in PEM format (optional). |
 | `calendars.*.auth` | dict | Authorization config for the calendar. |
 | `calendars.*.auth[].type` | string | Authorization type, one of `none` (no authorization), `basic` (HTTP Basic Authentication), `tls` (TLS client certificate). |

icalendar-timeseries-server.json

@@ -7,23 +7,26 @@
     "tz": "Europe/Zurich",
     "calendars": {
         "tlstest": {
+            "interval": "PT5M",
             "url": "https://localhost/private.ics",
             "ca": "/home/sebastian/tlstest/ca/ca/ca.crt",
             "auth": {
                 "type": "tls",
                 "keyfile": "/home/sebastian/tlstest/client/combined.pem"
             }
+        },
+        "filetest": {
+            "interval": "PT1M",
+            "url": "file:///srv/http/private.ics"
         }
     },
     "key_replace": {
         "summary": "a_summary",
-        "description": "b_description",
-        "calendar": "c_calendar"
+        "description": "b_description"
     },
     "value_replace": {
         "summary": "{{ summary|truncate(100, end=' \\N{HORIZONTAL ELLIPSIS}') }}",
         "description": "{{ description|truncate(100, end=' \\N{HORIZONTAL ELLIPSIS}') }}",
-        "calendar": "{{ 0 if calendar == 'private' else 1 }}",
         "useless_metric": "{{ start.timestamp() + end.timestamp() }}"
     }
 }

icalendar_timeseries_server/api.py

@@ -1,29 +1,21 @@
 from typing import List
 
 import json
-from datetime import datetime
 from urllib.error import HTTPError
 import traceback
 
 import bottle
-from isodate import Duration
 
 from icalendar_timeseries_server.config import get_config
-from icalendar_timeseries_server.event import Event
-from icalendar_timeseries_server.cal import scrape_calendar
+from icalendar_timeseries_server.event import Metric
+from icalendar_timeseries_server.cal import get_calendar
 from icalendar_timeseries_server.query import MetricQuery
 
 
 @bottle.route('/api/v1/query')
 @bottle.route('/api/v1/query_range')
 def prometheus_api():
-    tz = get_config().tz
-    now: datetime = datetime.now(tz)
-    start_delta: Duration = get_config().start_delta
-    end_delta: Duration = get_config().end_delta
-    start: datetime = now + start_delta
-    end: datetime = now + end_delta
-    events: List[Event] = []
+    events: List[Metric] = []
 
     try:
         q = MetricQuery(bottle.request.query['query'])
@@ -39,8 +31,8 @@ def prometheus_api():
         return json.dumps(response)
 
     try:
-        for name, caldef in get_config().calendars.items():
-            events.extend(scrape_calendar(name, caldef, start, end))
+        for name in get_config().calendars.keys():
+            events.extend(get_calendar(name))
         events = list(filter(q, events))
         events.sort(key=lambda e: e.start)
         response = {

icalendar_timeseries_server/cal.py

@@ -1,18 +1,20 @@
-from typing import Dict, List, Iterable, Tuple
+from typing import Dict, List, Iterable
 
 import sys
 import urllib.request
 from datetime import datetime, date, timedelta
+from threading import Timer
 
 from dateutil import rrule
 from icalendar import cal
+from isodate import Duration
 
 from icalendar_timeseries_server import __version__
 from icalendar_timeseries_server.config import get_config, CalendarConfig
 from icalendar_timeseries_server.event import Event
 
 
-_SCRAPE_CACHE: Dict[str, Tuple[datetime, List[Event]]] = dict()
+_SCRAPE_CACHE: Dict[str, List[Event]] = dict()
 
 __py_version: str = f'{sys.version_info.major}.{sys.version_info.minor}.{sys.version_info.micro}'
 USER_AGENT: str = f'icalendar-timeseries-server/{__version__} (Python/{__py_version})'
@@ -46,8 +48,15 @@ def _parse_recurring(event: cal.Event, start: datetime, end: datetime, duration:
     return occurences
 
 
-def _parse_calendar(name: str, calendar: cal.Calendar, start: datetime, end: datetime) -> List[Event]:
+def _scrape_calendar(name: str, config: CalendarConfig, start: datetime, end: datetime):
+    global _SCRAPE_CACHE
     events = []
+
+    opener: urllib.request.OpenerDirector = config.get_url_opener()
+    with opener.open(config.url) as response:
+        data = response.read().decode('utf-8')
+    calendar = cal.Calendar.from_ical(data)
+
     for element in calendar.walk():
         if element.name == "VEVENT":
             dtstart = element.get('dtstart').dt
@@ -70,23 +79,22 @@ def _parse_calendar(name: str, calendar: cal.Calendar, start: datetime, end: dat
             for occurence in occurences:
                 if start <= occurence < end:
                     events.append(Event(name, element, occurence, occurence + duration))
-    return events
+    _SCRAPE_CACHE[name] = events
 
 
-def scrape_calendar(name: str, config: CalendarConfig, start: datetime, end: datetime) -> List[Event]:
+def scrape_calendar(name: str, config: CalendarConfig):
+    tz = get_config().tz
+    now: datetime = datetime.now(tz)
+    start_delta: Duration = get_config().start_delta
+    end_delta: Duration = get_config().end_delta
+    start: datetime = now + start_delta
+    end: datetime = now + end_delta
+    _scrape_calendar(name, config, start, end)
+    cron = Timer(config.interval.totimedelta(start=now).total_seconds(),
+                 lambda: scrape_calendar(name, config))
+    cron.start()
+
+
+def get_calendar(name: str):
     global _SCRAPE_CACHE
-    now: datetime = datetime.now(tz=get_config().tz)
-    if get_config().cache.total_seconds() > 0 and name in _SCRAPE_CACHE:
-        cache_timeout, cached = _SCRAPE_CACHE[name]
-        if now < cache_timeout:
-            print('serving cached')
-            return cached
-    print('doing request')
-
-    opener: urllib.request.OpenerDirector = config.get_url_opener()
-    with opener.open(config.url) as response:
-        data = response.read().decode('utf-8')
-    calendar = cal.Calendar.from_ical(data)
-    parsed: List[Event] = _parse_calendar(name, calendar, start, end)
-    _SCRAPE_CACHE[name] = now + get_config().cache, parsed
-    return parsed
+    return _SCRAPE_CACHE.get(name, [])

icalendar_timeseries_server/config.py

@@ -27,6 +27,7 @@ class CalendarConfig:
 
     def __init__(self, config: Dict[str, Any], config_path: str) -> None:
         self._url: str = _keycheck('url', config, str, config_path)
+        self._scrape_interval: Duration = _parse_timedelta('interval', config, config_path, default_value='PT15M')
         self._ca: Optional[str] = _keycheck('ca', config, str, config_path, optional=True)
         auth: Dict[str, Any] = _keycheck('auth', config, dict, config_path, default_value={'type': 'none'})
         self._authtype: str = _keycheck('type', auth, str, f'{config_path}.auth',
@@ -56,6 +57,10 @@ class CalendarConfig:
     def url(self) -> str:
         return self._url
 
+    @property
+    def interval(self) -> Duration:
+        return self._scrape_interval
+
     def get_url_opener(self) -> urllib.request.OpenerDirector:
 
         if self._authtype == 'tls':
@@ -89,7 +94,6 @@ class Config:
         self._tz: pytz.tzinfo = _parse_timezone('tz', config, '', default_value='UTC')
         self._start_delta: Duration = _parse_timedelta('start_delta', config, '', default_value='PT')
         self._end_delta: Duration = _parse_timedelta('end_delta', config, '', default_value='P30D')
-        self._cache: Duration = _parse_timedelta('cache', config, '', default_value='PT', force_positive=True)
         self._calendars: Dict[str, CalendarConfig] = self._parse_calendars_config('calendars', config, '')
         self._key_replace = _parse_key_replace('key_replace', config, '')
         self._value_replace = _parse_value_replace('value_replace', config, '')
@@ -125,10 +129,6 @@ class Config:
     def end_delta(self) -> Duration:
         return self._end_delta
 
-    @property
-    def cache(self) -> Duration:
-        return self._cache
-
     @property
     def calendars(self) -> Dict[str, CalendarConfig]:
         return self._calendars

icalendar_timeseries_server/event.py

@@ -38,7 +38,7 @@ class Event(Metric):
         for attr in _ATTRIBUTES:
             tmp[attr] = event.get(attr, '')
         substitution_keys = set(_ATTRIBUTES)
-        substitution_keys.update(['start', 'end'])
+        substitution_keys.update(tmp.keys())
         substitution_keys.update(get_config().key_replace.keys())
         substitution_keys.update(get_config().value_replace.keys())
         for attr in substitution_keys:

icalendar_timeseries_server/main.py

@@ -2,6 +2,7 @@ import sys
 
 import bottle
 
+from icalendar_timeseries_server.cal import scrape_calendar
 from icalendar_timeseries_server.config import load_config, load_default_config, get_config
 
 # Contains decorated bottle handler function for /api/v1/query
@@ -17,7 +18,10 @@ def main():
     else:
         print(f'Can only read one config file, got "{" ".join(sys.argv[1:])}"')
         exit(1)
-    bottle.run(host=get_config().addr, port=get_config().port)
+    config = get_config()
+    for calname in config.calendars.keys():
+        scrape_calendar(calname, config.calendars[calname])
+    bottle.run(host=config.addr, port=get_config().port)
 
 
 if __name__ == '__main__':