Logs API: not possible to use without SDK

[lmolkova]

Let's assume I'm building a logging bridge for one of many python non-standard loggers (e.g. structlog).

I should be able to create a library using logging (bridge) API alone.

So I should write a code like:

from opentelemetry._logs import get_logger_provider
from opentelemetry._logs import LogRecord as APILogRecord

logger = get_logger_provider().get_logger(__name__)

logger.emit(APILogRecord(body="Hello, World!", attributes={"foo": "bar"}))

It'd fail with

opentelemetry\sdk\_logs\_internal\export\__init__.py", line 97, in <lambda>
    formatter: Callable[[LogRecord], str] = lambda record: record.to_json()
                                                           ^^^^^^^^^^^^^^
AttributeError: 'LogRecord' object has no attribute 'to_json'

Probably related to #3552

---

The recommendation

1. Make it possible to (properly) use Logs API alone without touching SDK types
2. Add example and tests that use vanilla logs API (with note that it's for logging bridges, not end users
3. Call API and SDK log records differently to minimize confusion. E.g. SDK one could be ReadWriteLogRecord and should probably replace LogData (see Logs SDK: consider removing LogData and extending SDK LogRecord to have instrumentation scope #4313)
4. Consider using a pattern similar to tracing when users don't need to instantiate a new span. Instead they could call logger.emit(....) with parameters and the SDK implementation of logger will create SDK implementation of LogRecord

Part of open-telemetry/community#1751

[lmolkova]

This is part of the same issue - if I try to use SDK LogRecord directly like in this snippet

from opentelemetry._logs import LogRecord as APILogRecord
from opentelemetry._logs import get_logger_provider
from opentelemetry.sdk._logs import LogRecord as SDKLogRecord

...
resource = Resource.create({"service.name": "test logs"})
logger_provider = LoggerProvider(resource=resource)
logger_provider.add_log_record_processor(SimpleLogRecordProcessor(ConsoleLogExporter()))
set_logger_provider(logger_provider)

logger = get_logger_provider().get_logger(__name__)

with trace_provider.get_tracer("example").start_as_current_span("foo"):
    logger.emit(SDKLogRecord(body="Hello, World!", attributes={"foo": "bar"}))

I get into the following issues:

1. I have to provide timestamp even though it's optional

       formatter: Callable[[LogRecord], str] = lambda record: record.to_json()
                                                              ^^^^^^^^^^^^^^^^
     File "opentelemetry\sdk\_logs\_internal\__init__.py", line 230, in to_json
       "timestamp": ns_to_iso_str(self.timestamp),
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     File "opentelemetry\sdk\util\__init__.py", line 27, in ns_to_iso_str
       nanoseconds / 1e9, tz=datetime.timezone.utc
       ~~~~~~~~~~~~^~~~~
   TypeError: unsupported operand type(s) for /: 'NoneType' and 'float'
   

2. If I provide it (logger.emit(SDKLogRecord(timestamp=time_ns(), body="Hello, World!", attributes={"foo": "bar"}))) I don't get resource attributes set

   {
       "body": "Hello, World!",
       "severity_number": "None",
       "severity_text": null,
       "attributes": {
           "foo": "bar"
       },
       "dropped_attributes": 0,
       "timestamp": "2024-11-24T19:48:29.322928Z",
       "observed_timestamp": "2024-11-24T19:48:29.322928Z",
       "trace_id": "",
       "span_id": "",
       "trace_flags": null,
       "resource": {
           "attributes": {
               "telemetry.sdk.language": "python",
               "telemetry.sdk.name": "opentelemetry",
               "telemetry.sdk.version": "1.28.2",
               "service.name": "unknown_service"
           },
           "schema_url": ""
       }
   }

3. Also you can see that trace-context is not set despite having valid current span