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fix: measure harvest intervals with a monotonic clock #106

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fix: measure harvest intervals with a monotonic clock #106

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10 changes: 6 additions & 4 deletions src/newrelic_telemetry_sdk/harvester.py
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,7 @@ def __init__(self, client, batch, harvest_interval=5):
self.client = client
self.batch = batch
self.harvest_interval = harvest_interval
self._harvest_interval_start = 0
self._harvest_interval_start = None
self._shutdown = self.EVENT_CLS()

def _send(self):
Expand All @@ -83,11 +83,13 @@ def _send(self):

def _wait_for_harvest(self):
"""Tracks and adjusts time required to maintain the harvest interval"""
current_time = time.time()
interval_start = self._harvest_interval_start or current_time
current_time = time.monotonic()
interval_start = self._harvest_interval_start
if interval_start is None:
interval_start = current_time
timeout = max(self.harvest_interval - (current_time - interval_start), 0)
shutdown = self._shutdown.wait(timeout)
self._harvest_interval_start = time.time()
self._harvest_interval_start = time.monotonic()
return shutdown

def run(self):
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19 changes: 18 additions & 1 deletion tests/test_harvester.py
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Original file line number Diff line number Diff line change
Expand Up @@ -202,7 +202,7 @@ def _wait(t):
timeout.append(t)
return True

monkeypatch.setattr(time, "time", _time, raising=True)
monkeypatch.setattr(time, "monotonic", _time, raising=True)
harvester._shutdown.wait = _wait

# First call should result in full timeout
Expand All @@ -217,3 +217,20 @@ def _wait(t):
def test_defaults(harvester):
assert harvester.daemon is True
assert harvester.harvest_interval == 5


@pytest.mark.parametrize("clock_change", [-3600, 3600])
def test_harvest_interval_ignores_wall_clock_changes(harvester, monkeypatch, clock_change):
wall_time = [10000]
elapsed_time = [100]
timeouts = []
monkeypatch.setattr(time, "time", lambda: wall_time[0])
monkeypatch.setattr(time, "monotonic", lambda: elapsed_time[0])
harvester._shutdown.wait = timeouts.append

harvester._wait_for_harvest()
wall_time[0] += clock_change
elapsed_time[0] += 2
harvester._wait_for_harvest()

assert timeouts == [5, 3]