1 files changed, 95 insertions, 0 deletions
diff --git a/tqdm/_monitor.py b/tqdm/_monitor.py
new file mode 100644
index 0000000..f71aa56
--- /dev/null
+++ b/tqdm/_monitor.py
@@ -0,0 +1,95 @@
+import atexit
+from threading import Event, Thread, current_thread
+from time import time
+from warnings import warn
+
+__all__ = ["TMonitor", "TqdmSynchronisationWarning"]
+
+
+class TqdmSynchronisationWarning(RuntimeWarning):
+    """tqdm multi-thread/-process errors which may cause incorrect nesting
+    but otherwise no adverse effects"""
+    pass
+
+
+class TMonitor(Thread):
+    """
+    Monitoring thread for tqdm bars.
+    Monitors if tqdm bars are taking too much time to display
+    and readjusts miniters automatically if necessary.
+
+    Parameters
+    ----------
+    tqdm_cls  : class
+        tqdm class to use (can be core tqdm or a submodule).
+    sleep_interval  : float
+        Time to sleep between monitoring checks.
+    """
+    _test = {}  # internal vars for unit testing
+
+    def __init__(self, tqdm_cls, sleep_interval):
+        Thread.__init__(self)
+        self.daemon = True  # kill thread when main killed (KeyboardInterrupt)
+        self.woken = 0  # last time woken up, to sync with monitor
+        self.tqdm_cls = tqdm_cls
+        self.sleep_interval = sleep_interval
+        self._time = self._test.get("time", time)
+        self.was_killed = self._test.get("Event", Event)()
+        atexit.register(self.exit)
+        self.start()
+
+    def exit(self):
+        self.was_killed.set()
+        if self is not current_thread():
+            self.join()
+        return self.report()
+
+    def get_instances(self):
+        # returns a copy of started `tqdm_cls` instances
+        return [i for i in self.tqdm_cls._instances.copy()
+                # Avoid race by checking that the instance started
+                if hasattr(i, 'start_t')]
+
+    def run(self):
+        cur_t = self._time()
+        while True:
+            # After processing and before sleeping, notify that we woke
+            # Need to be done just before sleeping
+            self.woken = cur_t
+            # Sleep some time...
+            self.was_killed.wait(self.sleep_interval)
+            # Quit if killed
+            if self.was_killed.is_set():
+                return
+            # Then monitor!
+            # Acquire lock (to access _instances)
+            with self.tqdm_cls.get_lock():
+                cur_t = self._time()
+                # Check tqdm instances are waiting too long to print
+                instances = self.get_instances()
+                for instance in instances:
+                    # Check event in loop to reduce blocking time on exit
+                    if self.was_killed.is_set():
+                        return
+                    # Only if mininterval > 1 (else iterations are just slow)
+                    # and last refresh exceeded maxinterval
+                    if (
+                        instance.miniters > 1
+                        and (cur_t - instance.last_print_t) >= instance.maxinterval
+                    ):
+                        # force bypassing miniters on next iteration
+                        # (dynamic_miniters adjusts mininterval automatically)
+                        instance.miniters = 1
+                        # Refresh now! (works only for manual tqdm)
+                        instance.refresh(nolock=True)
+                    # Remove accidental long-lived strong reference
+                    del instance
+                if instances != self.get_instances():  # pragma: nocover
+                    warn("Set changed size during iteration" +
+                         " (see https://github.com/tqdm/tqdm/issues/481)",
+                         TqdmSynchronisationWarning, stacklevel=2)
+                # Remove accidental long-lived strong references
+                del instances
+
+    def report(self):
+        return not self.was_killed.is_set()