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Fix limit env vars unset/unlimited values #2054

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Aug 24, 2021
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2 changes: 2 additions & 0 deletions CHANGELOG.md
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
([#2044](https://github.com/open-telemetry/opentelemetry-python/pull/2044))
- `opentelemetry-sdk` Fixed bugs (#2041, #2042 & #2045) in Span Limits
([#2044](https://github.com/open-telemetry/opentelemetry-python/pull/2044))
- `opentelemetry-sdk` Treat limit even vars set to empty values as unset/unlimited.
([#2044](https://github.com/open-telemetry/opentelemetry-python/pull/2054))
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- `opentelemetry-api` Attribute keys must be non-empty strings.
([#2057](https://github.com/open-telemetry/opentelemetry-python/pull/2057))

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15 changes: 9 additions & 6 deletions opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,7 @@
_DEFAULT_OTEL_LINK_ATTRIBUTE_COUNT_LIMIT = 128


_ENV_VALUE_UNSET = "unset"
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didn't we use unset so users should define it explicitly and can avoid the sudden surprise when not setting env either by no knowledge/ignorance considered as unlimited?

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We did but spec recommends using empty value as unlimited.

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We can try to convince others and update spec to accept "unset" as the value but for now I think we should update our SDK to make sure it is spec compatible.

_ENV_VALUE_UNSET = ""

# pylint: disable=protected-access
_TRACE_SAMPLER = sampling._get_from_env_or_default()
Expand Down Expand Up @@ -533,7 +533,7 @@ class SpanLimits:
- All limit arguments are optional.
- If a limit argument is not set, the class will try to read its value from the corresponding
environment variable.
- If the environment variable is not set, the default value for the limit is used.
- If the environment variable is not set, the default value, if any, will be used.

Args:
max_attributes: Maximum number of attributes that can be added to a Span.
Expand All @@ -553,7 +553,7 @@ class SpanLimits:
the specified length will be truncated.
"""

UNSET = -1
UNSET = "unset"

def __init__(
self,
Expand Down Expand Up @@ -609,15 +609,18 @@ def __repr__(self):
def _from_env_if_absent(
cls, value: Optional[int], env_var: str, default: Optional[int] = None
) -> Optional[int]:
if value is cls.UNSET:
if value == cls.UNSET:
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Maybe I'm not fully understanding this scenario. When will value ever be "unset"? Isn't value supposed to be an int?

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The API usage looks like the following in order to not set a limit:

SpanLimits(max_attributes=SpanLimits.UNSET)

SpanLimits.UNSET is a symbol that users can pass as a limit to set the limit to infinity. We can freely change its internal value to anything without breaking any contracts.

The reason why I used "unset" was that I thought -1 might be confusing as the spec disallows it for env vars. Internally we can still use -1 as the symbol value.

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Changed it back to -1 as this is probably causing more confusion and does not respect the function contract. I wonder why mypy didn't catch it.

return None

err_msg = "{0} must be a non-negative integer but got {}"

# if no value is provided for the limit, try to load it from env
if value is None:
str_value = environ.get(env_var, "").strip().lower()
if not str_value:
# return default value if env var is not set
if env_var not in environ:
return default

str_value = environ.get(env_var, "").strip().lower()
if str_value == _ENV_VALUE_UNSET:
return None

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8 changes: 4 additions & 4 deletions opentelemetry-sdk/tests/trace/test_trace.py
Original file line number Diff line number Diff line change
Expand Up @@ -1533,10 +1533,10 @@ def test_span_limits_code(self):
@mock.patch.dict(
"os.environ",
{
OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT: "unset",
OTEL_SPAN_EVENT_COUNT_LIMIT: "unset",
OTEL_SPAN_LINK_COUNT_LIMIT: "unset",
OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT: "unset",
OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT: "",
OTEL_SPAN_EVENT_COUNT_LIMIT: "",
OTEL_SPAN_LINK_COUNT_LIMIT: "",
OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT: "",
},
)
def test_span_no_limits_env(self):
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