add memory watch example

examples/when_ready.conf.py

@@ -0,0 +1,38 @@
+import signal
+import commands
+import threading
+import time
+
+max_mem = 100000
+
+class MemoryWatch(threading.Thread):
+    
+    def __init__(self, server, max_mem):
+        super(MemoryWatch, self).__init__()
+        self.daemon = True
+        self.server = server
+        self.max_mem = max_mem
+        self.timeout = server.timeout / 2
+
+    def memory_usage(self, pid):
+        try:
+            out = commands.getoutput("ps -o rss -p %s" % pid)
+        except IOError:
+            return -1
+        used_mem = sum(int(x) for x in out.split('\n')[1:])
+        return used_mem
+    
+        
+    def run(self):
+        while True:
+            for (pid, worker) in list(self.server.WORKERS.items()):
+                if self.memory_usage(pid) > self.max_mem:
+                    self.server.log.info("Pid %s killed (memory usage > %s)" % (
+                        pid, self.max_mem))
+                    self.server.kill_worker(pid, signal.SIGQUIT)
+            time.sleep(self.timeout)
+            
+
+def when_ready(server):
+    mw = MemoryWatch(server, max_mem)
+    mw.start()