Ensure ZK logging does not block startup

daemon-common/log.py

@@ -23,6 +23,7 @@ from collections import deque
 from threading import Thread
 from queue import Queue
 from datetime import datetime
+from time import sleep
 
 from daemon_lib.zkhandler import ZKHandler
 
@@ -83,7 +84,8 @@ class Logger(object):
         self.last_prompt = ''
 
         if self.config['zookeeper_logging']:
-            self.zookeeper_logger = ZookeeperLogger(config)
+            self.zookeeper_queue = Queue()
+            self.zookeeper_logger = ZookeeperLogger(self.config, self.zookeeper_queue)
             self.zookeeper_logger.start()
 
     # Provide a hup function to close and reopen the writer
@@ -96,9 +98,15 @@ class Logger(object):
         if self.config['file_logging']:
             self.writer.close()
         if self.config['zookeeper_logging']:
-            self.out("Waiting for Zookeeper message queue to drain", state='s')
-            while not self.zookeeper_logger.queue.empty():
-                pass
+            self.out("Waiting 15s for Zookeeper message queue to drain", state='s')
+
+            tick_count = 0
+            while not self.zookeeper_queue.empty():
+                sleep(0.5)
+                tick_count += 1
+                if tick_count > 30:
+                    break
+
             self.zookeeper_logger.stop()
             self.zookeeper_logger.join()
 
@@ -145,7 +153,7 @@ class Logger(object):
 
         # Log to Zookeeper
         if self.config['zookeeper_logging']:
-            self.zookeeper_logger.queue.put(message)
+            self.zookeeper_queue.put(message)
 
         # Set last message variables
         self.last_colour = colour
@@ -157,19 +165,14 @@ class ZookeeperLogger(Thread):
     Defines a threaded writer for Zookeeper locks. Threading prevents the blocking of other
     daemon events while the records are written. They will be eventually-consistent
     """
-    def __init__(self, config):
+    def __init__(self, config, zookeeper_queue):
         self.config = config
         self.node = self.config['node']
         self.max_lines = self.config['node_log_lines']
-        self.queue = Queue()
-        self.zkhandler = None
-        self.start_zkhandler()
-        # Ensure the root keys for this are instantiated
-        self.zkhandler.write([
-            ('base.logs', ''),
-            (('logs', self.node), '')
-        ])
+        self.zookeeper_queue = zookeeper_queue
+        self.connected = False
         self.running = False
+        self.zkhandler = None
         Thread.__init__(self, args=(), kwargs=None)
 
     def start_zkhandler(self):
@@ -179,10 +182,29 @@ class ZookeeperLogger(Thread):
                 self.zkhandler.disconnect()
             except Exception:
                 pass
+
+        while True:
+            try:
                 self.zkhandler = ZKHandler(self.config, logger=None)
                 self.zkhandler.connect(persistent=True)
+                break
+            except Exception:
+                sleep(0.5)
+                continue
+
+        self.connected = True
+
+        # Ensure the root keys for this are instantiated
+        self.zkhandler.write([
+            ('base.logs', ''),
+            (('logs', self.node), '')
+        ])
 
     def run(self):
+        while not self.connected:
+            self.start_zkhandler()
+            sleep(1)
+
         self.running = True
         # Get the logs that are currently in Zookeeper and populate our deque
         raw_logs = self.zkhandler.read(('logs.messages', self.node))
@@ -192,7 +214,7 @@ class ZookeeperLogger(Thread):
         while self.running:
             # Get a new message
             try:
-                message = self.queue.get(timeout=1)
+                message = self.zookeeper_queue.get(timeout=1)
                 if not message:
                     continue
             except Exception: