From 67dbdf90ac805e3cf45c3f8cab731bc451813d6c Mon Sep 17 00:00:00 2001
From: Christopher Usher <c.g.usher@ljmu.ac.uk>
Date: Wed, 12 Dec 2018 17:40:59 +0000
Subject: [PATCH] start of a rough prototype of the backfiller

---
 backfiller/backfiller.py | 83 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 backfiller/backfiller.py

diff --git a/backfiller/backfiller.py b/backfiller/backfiller.py
new file mode 100644
index 0000000..e585848
--- /dev/null
+++ b/backfiller/backfiller.py
@@ -0,0 +1,83 @@
+
+# this is a prototype of the backfiller
+# lots about web services and the like I don't know
+# needs logging, exception handling and the like
+
+import glob
+import requests
+import os
+
+
+def get_nodes():
+
+    # either read a config file or query the database to get the addresses of
+    # the other nodes
+
+    # as a prototype can just hardcode some addresses.
+
+    nodes = []
+
+    return nodes
+
+def list_remote_segments(node):
+
+    # return a list of paths
+    # obviously update path with real one
+
+    resp = requests.get(node + '/wubloader/segment_list')
+    remote_segments = resp.json() #replace with appropriate parser
+
+    return remote_segments
+
+#based on _get_segment in downloader/main
+#should have a more general shared version of this
+def get_remote_segment(node, segment):
+
+    # obviously update path with real one
+    resp = requests.get(node + '/wubloader/segments/' + segment, stream=True)
+
+    with open('temp_backfill', 'w') as f:
+        for chunk in resp.iter_content(8192):
+            f.write(chunk)
+
+    os.rename(temp, segment)
+
+
+
+def back_fill(base_dir, nodes=None):
+
+    # loop over nodes asking for a list of segments then downloads any segments
+    # it doesn't have
+
+    if nodes is None:
+        nodes = get_nodes()
+
+
+    for node in nodes:
+
+        # need to figure out how to properly check whether this node is the
+        # same
+        if node == 'localhost':
+            continue
+
+        # not sure how much we want to hard code the search
+        local_segments = set(glob.glob(base_dir + '/*/*/*.ts'))
+
+        remote_segments = set(list_remote_segments(node))
+
+        missing_segments = remote_segments - local_segments
+
+        
+        for missing_segment in missing_segments:
+            get_remote_segment(node, missing_segment)
+
+
+
+def main(base_dir, wait_time=60):
+
+    None
+    # every wait_time call back_fill
+    # time from start of back_fill
+    # to keep things simple don't try two back_fills at the same time
+    # wait for previous one to start before launching second.
+    # if it's taken more than wait_time for back_fill to run, start immediately