flush() doesn't clear properties

[benkehoe]

According the README, flush() "[f]lushes the current MetricsContext to the configured sink and resets all properties, dimensions and metric values. The namespace and default dimensions will be preserved across flushes."

However, in MetricContext.create_copy_with_context(), which is used by MetricsLogger.flush() to reset the context, copies the old properties. This means in my Lambda function, if I have conditional properties in my logging object, once I've set one in one invocation, it remains present in the context in future invocations.

[benkehoe]

I'm currently working around this by called metrics.context.properties.clear() at the beginning of my handler. I'd be up for contributing a fix. My preference would be to change the signature to MetricContext.create_copy_with_context(copy_properties=True) to preserve its default behavior, and change MetricsLogger.flush() to set this to false to make its behavior match the spec. Let me know if this would be acceptable.

[rstevens011]

I had a case where in the lambda handler with a property set inside a for loop, only a single EMF string would be printed to the log group with only the last iteration printed to the log stream. A simple example:

@metric_scope
def lambda_handler(event, context, metrics):
    foo = [ "bar", "bars"]
    for idx, x in enumerate(foo):
        metrics.set_property("property_name", x)
        metrics.put_metric("metric_name", float(idx))

This would result in a log stream entry with property_name being set to bars. I feel like this is a similar problem to the OP's and could be the same root cause. Thoughts?