python_pinger.git

@@ -54,8 +54,8 @@ Multi-threaded ping calls won't block each other.

 ### Downsides

-The ping tasks read from, and write to a shared dictionary. (Reading and

-updating the last status.)

+The ping tasks read from, and write to a shared dictionary, so they need

+to serialize that access.

 ## Short Lived Workers

@@ -74,7 +74,7 @@ The worker tasks aren't in memory if they're not doing anything. So usually a sm

 ### Downsides

-The ping tasks still read from, and write to a shared dictionary. (Reading and updating the last status.)

+The ping tasks still read from, and write to that shared dictionary, so they serialize that access.

 ## Long Lived Looping Workers

@@ -13,6 +13,8 @@ from argparse import ArgumentParser

 import threading

 import queue

+pinger_lock = threading.Lock()

+

 def pinger():

     """Each queue item is a new address to ping. Ping and compare and print.

@@ -22,10 +24,14 @@ def pinger():

         host = _ping_queue.get()

         now = time.localtime()

         success = ping(host)

-        if success != _results[host]:

+        with pinger_lock:

+            # Access to _results needs to be serialized

+            need_update = success != _results[host]

+            if need_update:

+                _results[host] = success

+        if need_update:

             status = "UP" if success else "DOWN"

             _print_queue.put([f'{time.strftime("%Y-%m-%d %H:%M:%S", now)} {host} {status}'])

-            _results[host] = success

         _ping_queue.task_done()

@@ -13,15 +13,21 @@ from argparse import ArgumentParser

 import threading

 import queue

+pinger_lock = threading.Lock()

+

 def pinger(host):

     """Executes one ping, prints if there was a change, exits thread."""

     now = time.localtime()

     success = ping(host)

-    if success != _results[host]:

+    with pinger_lock:

+        # Access to _results needs to be serialized

+        need_update = success != _results[host]

+        if need_update:

+            _results[host] = success

+    if need_update:

         status = "UP" if success else "DOWN"

         _print_queue.put([f'{time.strftime("%Y-%m-%d %H:%M:%S", now)} {host} {status}'])

-        _results[host] = success

 def ping(host):