sync_es: die when killed

sync_es.py

@@ -24,6 +24,10 @@ database into es, at the expense of redoing a (small) amount of indexing.
 
 This uses multithreading so we don't have to block on socket io (both binlog
 reading and es POSTing). asyncio soon™
+
+This script will exit on any sort of exception, so you'll want to use your
+supervisor's restart functionality, e.g. Restart=failure in systemd, or
+the poor man's `while true; do sync_es.py; sleep 1; done` in tmux.
 """
 from elasticsearch import Elasticsearch
 from elasticsearch.helpers import bulk, BulkIndexError
@@ -133,14 +137,31 @@ def delet_this(row, index_name):
         '_type': 'torrent',
         '_id': str(row['values']['id'])}
 
+# we could try to make this script robust to errors from es or mysql, but since
+# the only thing we can do is "clear state and retry", it's easier to leave
+# this to the supervisor. If we we carrying around heavier state in-process,
+# it'd be more worth it to handle errors ourselves.
+# 
+# Apparently there's no setDefaultUncaughtExceptionHandler in threading, and
+# sys.excepthook is also broken, so this gives us the same
+# exit-if-anything-happens semantics. 
+class ExitingThread(Thread):
+    def run(self):
+        try:
+            self.run_happy()
+        except:
+            log.exception("something happened")
+            # sys.exit only exits the thread, lame
+            import os
+            os._exit(1)
 
-class BinlogReader(Thread):
+class BinlogReader(ExitingThread):
     # write_buf is the Queue we communicate with
     def __init__(self, write_buf):
         Thread.__init__(self)
         self.write_buf = write_buf
 
-    def run(self):
+    def run_happy(self):
         with open(SAVE_LOC) as f:
             pos = json.load(f)
 
@@ -229,7 +250,7 @@ class BinlogReader(Thread):
             else:
               raise Exception(f"unknown table {s.table}")
 
-class EsPoster(Thread):
+class EsPoster(ExitingThread):
     # read_buf is the queue of stuff to bulk post
     def __init__(self, read_buf, chunk_size=1000, flush_interval=5):
         Thread.__init__(self)
@@ -237,7 +258,7 @@ class EsPoster(Thread):
         self.chunk_size = chunk_size
         self.flush_interval = flush_interval
 
-    def run(self):
+    def run_happy(self):
         es = Elasticsearch(timeout=30)
 
         last_save = time.time()