ersalil commented on issue #68282:
URL: https://github.com/apache/airflow/issues/68282#issuecomment-4659456560
## Additional findings worth noting
### 1. The OTel SDK error message is misleading
The crash shows `"Expected ASCII string of maximum length 63 characters"`
which makes it look like a length problem. It is not.
I verified that the installed OTel Python SDK (`opentelemetry-sdk 1.42.1`)
actually validates instrument names against the regex
`[a-zA-Z][-_./a-zA-Z0-9]{0,254}`, which allows **up to 255 characters** —
matching Airflow's own `OTEL_NAME_MAX_LENGTH = 255`. The `"63 characters"` in
the error message is a [stale string left
over](https://github.com/open-telemetry/opentelemetry-python/blob/main/opentelemetry-sdk/src/opentelemetry/sdk/metrics/_internal/instrument.py#L48C1-L50C2)
from an older version of the OTel spec. The actual validation was updated to
255 chars in
[open-telemetry/opentelemetry-python#3442](https://github.com/open-telemetry/opentelemetry-python/pull/3442)
(released in v1.21.0, September 2023), but the error message string was never
updated alongside it.
The real reason the name is rejected is the **space character** in
`PBI_SKU_Performance copy`, which is not in the allowed character set. Length
is not the issue here.
### 2. `gauge()` was missing the `name_is_otel_safe()` guard
`incr()`, `decr()`, and `timing()` all gate metric emission behind two
checks:
```python
if self.metrics_validator.test(stat) and name_is_otel_safe(self.prefix,
stat):
...
gauge() only had the first check:
if self.metrics_validator.test(stat): # no name_is_otel_safe()
...
```
The metrics_validator only filters by allow/block list patterns — it knows
nothing about OTel naming rules. So the space in PBI_SKU_Performance copy
passed straight through it and reached meter.create_gauge() inside the OTel
SDK, which raised the (misleading) exception uncaught, crashing the
DagProcessor.
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