Forward-port from ZODB 3.2.

Collector 1503:  excessive logging.

ClientStorage._wait_sync():  Don't log more than one "waiting for cache
verification to finish" message per 5 minutes.

NEWS.txt

@@ -25,6 +25,15 @@ ZEO client cache
 - Fixed a bug wherein an object removed from the client cache didn't
   properly mark the file slice it occupied as being available for reuse.
 
+ZEO
+---
+
+Collector 1503:  excessive logging.  It was possible for a ZEO client to
+log "waiting for cache verification to finish" messages at a very high
+rate, producing gigabytes of such messages in short order.
+``ClientStorage._wait_sync()`` was changed to log no more than one
+such message per 5 minutes.
+
 persistent
 ----------
 
@@ -59,7 +68,6 @@ made, it was possible for the pack routine to die with a reference to an
 undefined global while it was trying to raise ``CorruptedError``.  It
 raises ``CorruptedError``, as it always intended, in these cases now.
 
-
 Install
 -------
 

src/ZEO/ClientStorage.py

@@ -353,20 +353,28 @@ class ClientStorage(object):
             self._wait_sync(deadline)
 
     def _wait_sync(self, deadline=None):
-        # If there is no mainloop running, this code needs
-        # to call poll() to cause asyncore to handle events.
-        while 1:
-            if self._ready.isSet():
-                break
-            if deadline and time.time() > deadline:
+        # Log no more than one "waiting" message per LOG_THROTTLE seconds.
+        LOG_THROTTLE = 300 # 5 minutes
+        next_log_time = time.time()
+
+        while not self._ready.isSet():
+            now = time.time()
+            if deadline and now > deadline:
                 log2("Timed out waiting for connection", level=logging.WARNING)
                 break
+            if now >= next_log_time:
                 log2("Waiting for cache verification to finish")
+                next_log_time = now + LOG_THROTTLE
             if self._connection is None:
                 # If the connection was closed while we were
                 # waiting for it to become ready, start over.
-                return self._wait(deadline - time.time())
+                if deadline is None:
+                    timeout = None
                 else:
+                    timeout = deadline - now
+                return self._wait(timeout)
+            # No mainloop ia running, so we need to call something fancy to
+            # handle asyncore events.
             self._connection.pending(30)
 
     def close(self):