Unblocking myself.


A simple fix is to not wait before the last flush when the flushing process exits.

This will bring our flushing process' behavior in line with ts_mon's own flushing thread implementation: https://cs.corp.google.com/chromeos_public/chromite/third_party/infra_libs/ts_mon/common/interface.py?l=174

A quick search of the history of chromite/lib/ts_mon_config.py doesn't tell me that we added the final delay to the flush in response to a bug.

I can see how it keeps things more "correct":
- We don't run the risk of sending a metric too soon and getting rejected somewhere in the pipeline
- We ensure that the last flush does not screw up rate calculations.

BUT,
- This is causing delays that are significant enough to cause failures
- This behaviour is different from using ts_mon's flushing (so rate calculations will differ slightly based on what flags mode we use ts_mon in).

The CL to remove this is trivial. Figuring out the impact is a bit harder.

Go for it (if it's easy to do), I suspect the impacts of what you propose are benign.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/04e59d08c79c73ca15997383552314c32f95a86b

commit 04e59d08c79c73ca15997383552314c32f95a86b
Author: Prathmesh Prabhu <pprabhu@chromium.org>
Date: Fri Dec 02 19:42:39 2016

metrics: Don't wait before flushing last metrics.

This CL removes a wait before the metrics handling process flushes it's
last metrics. This means that the last metrics may be flushed at an
interval smaller than usual. This can impact the rate computation of
metrics on the backend.

But, this wait needs to go because it was causing delays in process
exits leading to test failures. (The extra sleep of ~ 60 seconds is too
much at the end of a task).

BUG= chromium:670548 
TEST=unittests. No live testing.

Change-Id: I9272b6574080c3013c46c5ac53b57fe950ecced0
Reviewed-on: https://chromium-review.googlesource.com/416308
Commit-Ready: Prathmesh Prabhu <pprabhu@chromium.org>
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>

[modify] https://crrev.com/04e59d08c79c73ca15997383552314c32f95a86b/lib/ts_mon_config.py
[modify] https://crrev.com/04e59d08c79c73ca15997383552314c32f95a86b/lib/ts_mon_config_unittest.py

Will be verified if my blocked CLs pass ;)