New tryDownload/tryUpload methods

slapos/libnetworkcache.py

@@ -286,6 +286,25 @@ class NetworkcacheClient(object):
       connection.close()
     raise HTTPError(url, r.status, r.reason, r.msg, r.fp)
 
+  def tryDownload(self, key):
+    """
+    To be called before attemting to download from network cache.
+    bool(returned value) is True if that possible (i.e. configured),
+    - in which case the method logs what's going to happen;
+    - else the caller should continue without network cache.
+    """
+    config_get = self.config.get
+    if config_get('download-dir-url') and config_get('download-cache-url'):
+      logger.info('Trying to download %s from network cache...', key)
+      return True
+
+  def tryUpload(self, key):
+    """Similar to tryDownload but for upload"""
+    config_get = self.config.get
+    if config_get('upload-dir-url') and config_get('upload-cache-url'):
+      logger.info('Trying to upload %s to network cache...', key)
+      return True
+
   @staticmethod
   def archive(path):
     # Don't create it to /tmp dir as it can be too small.