Add a worker to automatically GC expired app specific tokens

Fixes https://jira.coreos.com/browse/QUAY-822

workers/expiredappspecifictokenworker.py

@@ -0,0 +1,49 @@
+import logging
+import time
+
+import features
+
+from app import app # This is required to initialize the database.
+from data import model
+from workers.worker import Worker
+from util.log import logfile_path
+from util.timedeltastring import convert_to_timedelta
+
+POLL_PERIOD_SECONDS = 60 * 60 # 1 hour
+
+logger = logging.getLogger(__name__)
+
+class ExpiredAppSpecificTokenWorker(Worker):
+  def __init__(self):
+    super(ExpiredAppSpecificTokenWorker, self).__init__()
+
+    expiration_window = app.config.get('EXPIRED_APP_SPECIFIC_TOKEN_GC', '1d')
+    self.expiration_window = convert_to_timedelta(expiration_window)
+
+    logger.debug('Found expiration window: %s', expiration_window)
+    self.add_operation(self._gc_expired_tokens, POLL_PERIOD_SECONDS)
+
+  def _gc_expired_tokens(self):
+    """ Garbage collects any expired app specific tokens outside of the configured
+        window. """
+    logger.debug('Garbage collecting expired app specific tokens with window: %s',
+                 self.expiration_window)
+    model.appspecifictoken.gc_expired_tokens(self.expiration_window)
+    return True
+
+if __name__ == "__main__":
+  logging.config.fileConfig(logfile_path(debug=False), disable_existing_loggers=False)
+
+  if not features.APP_SPECIFIC_TOKENS:
+    logger.debug('App specific tokens disabled; skipping')
+    while True:
+      time.sleep(100000)
+  
+  if app.config.get('EXPIRED_APP_SPECIFIC_TOKEN_GC') is None:
+    logger.debug('GC of App specific tokens is disabled; skipping')
+    while True:
+      time.sleep(100000)
+
+  logger.debug('Starting expired app specific token GC worker')
+  worker = ExpiredAppSpecificTokenWorker()
+  worker.start()