def test_probability_sampler_limits(self):
# Sample one of every 2^64 (= 5e-20) traces. This is the lowest
# possible meaningful sampling rate, only traces with trace ID 0x0
# should get sampled.
almost_always_off = sampling.ProbabilitySampler(2**-64)
self.assertTrue(
almost_always_off.should_sample(None, 0x0, 0xDEADBEEF,
"span name").sampled)
self.assertFalse(
almost_always_off.should_sample(None, 0x1, 0xDEADBEEF,
"span name").sampled)
self.assertEqual(
sampling.ProbabilitySampler.get_bound_for_rate(2**-64), 0x1)
# Sample every trace with (last 8 bytes of) trace ID less than
# 0xffffffffffffffff. In principle this is the highest possible
# sampling rate less than 1, but we can't actually express this rate as
# a float!
#
# In practice, the highest possible sampling rate is:
#
# round(sys.float_info.epsilon * 2 ** 64)
almost_always_on = sampling.ProbabilitySampler(1 - 2**-64)
self.assertTrue(
almost_always_on.should_sample(None, 0xFFFFFFFFFFFFFFFE,
0xDEADBEEF, "span name").sampled)
def test_probability_sampler_limits(self):
# Sample one of every 2^64 (= 5e-20) traces. This is the lowest
# possible meaningful sampling rate, only traces with trace ID 0x0
# should get sampled.
almost_always_off = sampling.ProbabilitySampler(2**-64)
self.assertTrue(
almost_always_off.should_sample(None, 0x0, 0xDEADBEEF,
"span name").sampled)
self.assertFalse(
almost_always_off.should_sample(None, 0x1, 0xDEADBEEF,
"span name").sampled)
self.assertEqual(
sampling.ProbabilitySampler.get_bound_for_rate(2**-64), 0x1)
# Sample every trace with trace ID less than 0xffffffffffffffff. In
# principle this is the highest possible sampling rate less than 1, but
# we can't actually express this rate as a float!
#
# In practice, the highest possible sampling rate is:
#
# 1 - sys.float_info.epsilon
almost_always_on = sampling.ProbabilitySampler(1 - 2**-64)
self.assertTrue(
almost_always_on.should_sample(None, 0xFFFFFFFFFFFFFFFE,
0xDEADBEEF, "span name").sampled)
# These tests are logically consistent, but fail because of the float
# precision issue above. Changing the sampler to check fewer bytes of
# the trace ID will cause these to pass.
# self.assertFalse(
# almost_always_on.should_sample(
# None,
# 0xFFFFFFFFFFFFFFFF,
# 0xDEADBEEF,
# "span name",
# ).sampled
# )
# self.assertEqual(
# sampling.ProbabilitySampler.get_bound_for_rate(1 - 2 ** -64)),
# 0xFFFFFFFFFFFFFFFF,
# )
# Check that a sampler with the highest effective sampling rate < 1
# refuses to sample traces with trace ID 0xffffffffffffffff.
almost_almost_always_on = sampling.ProbabilitySampler(
1 - sys.float_info.epsilon)
self.assertFalse(
almost_almost_always_on.should_sample(None, 0xFFFFFFFFFFFFFFFF,
0xDEADBEEF,
"span name").sampled)
# Check that the higest effective sampling rate is actually lower than
# the highest theoretical sampling rate. If this test fails the test
# above is wrong.
self.assertLess(
almost_almost_always_on.bound,
0xFFFFFFFFFFFFFFFF,
)
def test_probability_sampler(self):
sampler = sampling.ProbabilitySampler(0.5)
# Check that we sample based on the trace ID if the parent context is
# null
self.assertTrue(
sampler.should_sample(None, 0x7FFFFFFFFFFFFFFF, 0xDEADBEEF,
"span name").sampled)
self.assertFalse(
sampler.should_sample(None, 0x8000000000000000, 0xDEADBEEF,
"span name").sampled)
# Check that the sampling decision matches the parent context if given,
# and that the sampler ignores the trace ID
self.assertFalse(
sampler.should_sample(
trace.SpanContext(0xDEADBEF0,
0xDEADBEF1,
trace_options=TO_DEFAULT),
0x8000000000000000,
0xDEADBEEF,
"span name",
).sampled)
self.assertTrue(
sampler.should_sample(
trace.SpanContext(0xDEADBEF0,
0xDEADBEF1,
trace_options=TO_SAMPLED),
0x8000000000000001,
0xDEADBEEF,
"span name",
).sampled)
def test_probability_sampler_one(self):
default_off = sampling.ProbabilitySampler(1.0)
self.assertTrue(
default_off.should_sample(None, 0xFFFFFFFFFFFFFFFF, 0xDEADBEEF,
"span name").sampled)
def test_probability_sampler_zero(self):
default_off = sampling.ProbabilitySampler(0.0)
self.assertFalse(
default_off.should_sample(None, 0x0, 0xDEADBEEF,
"span name").sampled)