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rospy.loginfo_throttle and _throttle_identical

asked 2019-07-28 13:05:21 -0500

pitosalas gravatar image

A few simple logging questions:

  1. How does throttle decide that the message is the same and not a different log message? Is it simply by the call site?

  2. Also what are the units for throttle? The doc seems to imply that it is seconds but for me it's not doing any throttling.

  3. Finally, what exactly would _throttle_identical do? How does it determine whether it's identical?


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answered 2021-01-14 10:07:42 -0500

lucasw gravatar image

updated 2021-01-14 10:32:53 -0500

I didn't know rospy.loginfo_throttle_identical() and the others existed until seeing this, it looks like it has been in the code for a few years (if not any documentation or open source ros projects). I'll have to start using it (check for C++ equivalents).

From trying it out and looking at the code throttle_identical behaves like throttle except if the message text changes. The timer doesn't reset if the message changes, it will stay on the previous throttle phase.

This can be demonstrated on the python shell (every line must have the same caller id):

rospy.loginfo_throttle_identical(10.0, "test1");
rospy.loginfo_throttle_identical(10.0, "test1");  # doesn't log  'test1' == 'test1'
rospy.loginfo_throttle_identical(10.0, "test2");  # does log, 'test2' != 'test1'
rospy.loginfo_throttle_identical(10.0, "test1");  # does log, 'test1' != 'test2'
rospy.loginfo_throttle_identical(10.0, "test1");  # does log, time elapsed since first log expired

Here it hashes on the message (as opposed to a string comparison) and uses the caller_id (probably source function + line number)

class LoggingIdentical(object):

    last_logging_msg_table = {}

    def __call__(self, caller_id, msg):
        """Do logging specified message only if distinct from last message.
        - caller_id (str): Id to identify the caller
        - msg (str): Contents of message to log
        msg_hash = md5(msg).hexdigest()

        if msg_hash != self.last_logging_msg_table.get(caller_id):
            self.last_logging_msg_table[caller_id] = msg_hash
            return True
        return False

There's no loginfo_identical but the same could be accomplished with a very long throttle period loginfo_throttle_identical(1000000.0, ...).

(What I'd like is a throttle with an exponential falloff parameter, it would repeat but at an increasingly long period until reset. Also it would be nice to get a bool feedback from the log throttle call if a log occurred or not.)

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Asked: 2019-07-28 13:05:21 -0500

Seen: 1,258 times

Last updated: Jan 14 '21