Merge pull request #208 from nyaadevs/die-sync-es

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)
@@ -237,30 +258,34 @@ 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()
         since_last = 0
+        # XXX keep track of last posted position for save points, awkward
+        posted_log_file = None
+        posted_log_pos = None
 
         while True:
             actions = []
-            while len(actions) < self.chunk_size:
+            now = time.time()
+            # wait up to flush_interval seconds after starting the batch
+            deadline = now + self.flush_interval
+            while len(actions) < self.chunk_size and now < deadline:
+                timeout = deadline - now
                 try:
                     # grab next event from queue with metadata that creepily
                     # updates, surviving outside the scope of the loop
                     ((log_file, log_pos, timestamp), action) = \
-                            self.read_buf.get(block=True, timeout=self.flush_interval)
+                            self.read_buf.get(block=True, timeout=timeout)
                     actions.append(action)
+                    now = time.time()
                 except Empty:
                     # nothing new for the whole interval
                     break
 
-            if not actions:
+            if actions:
-                # nothing to post
-                log.debug("no changes...")
-                continue
-
                 # XXX "time" to get histogram of no events per bulk
                 stats.timing('actions_per_bulk', len(actions))
 
@@ -279,17 +304,26 @@ class EsPoster(Thread):
                         except KeyError:
                             raise bie
 
+                # how far we've gotten in the actual log
+                posted_log_file = log_file
+                posted_log_pos = log_pos
+
                 # how far we're behind, wall clock
                 stats.gauge('process_latency', int((time.time() - timestamp) * 1000))
+            else:
+                log.debug("no changes...")
 
             since_last += len(actions)
-            if since_last >= 10000 or (time.time() - last_save) > 10:
+            # TODO instead of this manual timeout loop, could move this to another queue/thread
+            if posted_log_file is not None and (since_last >= 10000 or (time.time() - last_save) > 10):
                 log.info(f"saving position {log_file}/{log_pos}, {time.time() - timestamp:,.3f} seconds behind")
                 with stats.timer('save_pos'):
                     with open(SAVE_LOC, 'w') as f:
-                        json.dump({"log_file": log_file, "log_pos": log_pos}, f)
+                        json.dump({"log_file": posted_log_file, "log_pos": posted_log_pos}, f)
                 last_save = time.time()
                 since_last = 0
+                posted_log_file = None
+                posted_log_pos = None
 
 # in-memory queue between binlog and es. The bigger it is, the more events we
 # can parse in memory while waiting for es to catch up, at the expense of heap.