[SigV4] Better Error Handling and More Log Messages (#344)

*Description of changes:*
Added better logging messages for using SigV4 and a more graceful way to
handle the case where botocore is not installed to avoid this error
message:
```AttributeError: 'OtlpAwsSpanExporter' object has no attribute 'boto_aws_request'```


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Author: liustve

aws-opentelemetry-distro/src/amazon/opentelemetry/distro/aws_opentelemetry_configurator.py

@@ -319,10 +319,18 @@ def _customize_exporter(span_exporter: SpanExporter, resource: Resource) -> Span
             traces_endpoint = os.environ.get(AWS_XRAY_DAEMON_ADDRESS_CONFIG, "127.0.0.1:2000")
             span_exporter = OTLPUdpSpanExporter(endpoint=traces_endpoint)
 
-    if isinstance(span_exporter, OTLPSpanExporter) and is_xray_otlp_endpoint(
-        os.environ.get(OTEL_EXPORTER_OTLP_TRACES_ENDPOINT)
-    ):
-        span_exporter = OTLPAwsSpanExporter(endpoint=os.getenv(OTEL_EXPORTER_OTLP_TRACES_ENDPOINT))
+    if is_xray_otlp_endpoint(os.environ.get(OTEL_EXPORTER_OTLP_TRACES_ENDPOINT)):
+        # TODO: Change this url once doc writer has added a section for using SigV4 without collector
+        _logger.info("Detected using AWS OTLP XRay Endpoint.")
+
+        if isinstance(span_exporter, OTLPSpanExporter):
+            span_exporter = OTLPAwsSpanExporter(endpoint=os.getenv(OTEL_EXPORTER_OTLP_TRACES_ENDPOINT))
+
+        else:
+            _logger.warning(
+                "Improper configuration see: please export/set "
+                "OTEL_EXPORTER_OTLP_TRACES_PROTOCOL=http/protobuf and OTEL_TRACES_EXPORTER=otlp"
+            )
 
     if not _is_application_signals_enabled():
         return span_exporter
@@ -456,7 +464,6 @@ def _is_lambda_environment():
 
 def is_xray_otlp_endpoint(otlp_endpoint: str = None) -> bool:
     """Is the given endpoint the XRay OTLP endpoint?"""
-
     if not otlp_endpoint:
         return False
 

aws-opentelemetry-distro/src/amazon/opentelemetry/distro/otlp_aws_span_exporter.py

@@ -35,7 +35,7 @@ def __init__(
     ):
 
         self._aws_region = None
-
+        self._has_required_dependencies = False
         # Requires botocore to be installed to sign the headers. However,
         # some users might not need to use this exporter. In order not conflict
         # with existing behavior, we check for botocore before initializing this exporter.
@@ -52,6 +52,7 @@ def __init__(
             # The only usecase for this class would be for ADOT Python Auto Instrumentation and that already validates
             # the endpoint to be an XRay OTLP endpoint.
             self._aws_region = endpoint.split(".")[1]
+            self._has_required_dependencies = True
 
         else:
             _logger.error(
@@ -74,23 +75,26 @@ def __init__(
     # the same except if the endpoint is an XRay OTLP endpoint, we will sign the request
     # with SigV4 in headers before sending it to the endpoint. Otherwise, we will skip signing.
     def _export(self, serialized_data: bytes):
-        request = self.boto_aws_request.AWSRequest(
-            method="POST",
-            url=self._endpoint,
-            data=serialized_data,
-            headers={"Content-Type": "application/x-protobuf"},
-        )
+        if self._has_required_dependencies:
+            request = self.boto_aws_request.AWSRequest(
+                method="POST",
+                url=self._endpoint,
+                data=serialized_data,
+                headers={"Content-Type": "application/x-protobuf"},
+            )
 
-        credentials = self.boto_session.get_credentials()
+            credentials = self.boto_session.get_credentials()
 
-        if credentials is not None:
-            signer = self.boto_auth.SigV4Auth(credentials, AWS_SERVICE, self._aws_region)
+            if credentials is not None:
+                signer = self.boto_auth.SigV4Auth(credentials, AWS_SERVICE, self._aws_region)
 
-            try:
-                signer.add_auth(request)
-                self._session.headers.update(dict(request.headers))
+                try:
+                    signer.add_auth(request)
+                    self._session.headers.update(dict(request.headers))
 
-            except Exception as signing_error:  # pylint: disable=broad-except
-                _logger.error("Failed to sign request: %s", signing_error)
+                except Exception as signing_error:  # pylint: disable=broad-except
+                    _logger.error("Failed to sign request: %s", signing_error)
+        else:
+            _logger.debug("botocore is not installed. Failed to sign request to export traces to: %s", self._endpoint)
 
         return super()._export(serialized_data)