Add deprecation message for using instrumentation key (census-instrumentation#1118)

Author: lzchen

contrib/opencensus-ext-azure/CHANGELOG.md

@@ -6,6 +6,8 @@
 ([#1113](https://github.com/census-instrumentation/opencensus-python/pull/1113))
 - Statsbeat bug fixes - do not log if statsbeat
 ([#1116](https://github.com/census-instrumentation/opencensus-python/pull/1116))
+- Add deprecation warning for explicitly using instrumentation key
+([#1118](https://github.com/census-instrumentation/opencensus-python/pull/1118))
 
 ## 1.1.3
 Released 2022-03-03

contrib/opencensus-ext-azure/opencensus/ext/azure/common/__init__.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import logging
 import os
 import tempfile
 
@@ -21,6 +22,8 @@
 INSTRUMENTATION_KEY = 'instrumentationkey'
 TEMPDIR_PREFIX = "opencensus-python-"
 
+_logger = logging.getLogger(__name__)
+
 
 def process_options(options):
     # Connection string/ikey
@@ -30,6 +33,13 @@ def process_options(options):
         os.getenv('APPLICATIONINSIGHTS_CONNECTION_STRING'))
     env_ikey = os.getenv('APPINSIGHTS_INSTRUMENTATIONKEY')
 
+    # Deprecation note about explicit instrumentation key usage
+    if (not code_cs and code_ikey) or (not env_cs and env_ikey):
+        _logger.warning(
+            "DeprecationWarning: Explicitly using instrumentation key is"
+            "deprecated. Please use a connection string instead."
+        )
+
     # The priority of which value takes on the instrumentation key is:
     # 1. Key from explicitly passed in connection string
     # 2. Key from explicitly passed in instrumentation key