Add missing environment variables

Author: ocelotl

Diff for: opentelemetry-sdk/src/opentelemetry/sdk/environment_variables.py

@@ -500,3 +500,45 @@
 
 The :envvar:`OTEL_EXPORTER_JAEGER_GRPC_INSECURE` is a boolean flag to True if collector has no encryption or authentication.
 """
+
+OTEL_METRIC_EXPORT_INTERVAL = "OTEL_METRIC_EXPORT_INTERVAL"
+"""
+.. envvar:: OTEL_METRIC_EXPORT_INTERVAL
+
+The :envvar:`OTEL_METRIC_EXPORT_INTERVAL` is the time interval (in milliseconds) between the start of two export attempts.
+"""
+
+OTEL_METRIC_EXPORT_TIMEOUT = "OTEL_METRIC_EXPORT_TIMEOUT"
+"""
+.. envvar:: OTEL_METRIC_EXPORT_TIMEOUT
+
+The :envvar:`OTEL_METRIC_EXPORT_TIMEOUT` is the maximum allowed time (in milliseconds) to export data.
+"""
+
+OTEL_EXPORTER_OTLP_METRICS_CLIENT_KEY = "OTEL_EXPORTER_OTLP_METRICS_CLIENT_KEY"
+"""
+.. envvar:: OTEL_EXPORTER_OTLP_METRICS_CLIENT_KEY
+
+The :envvar:`OTEL_EXPORTER_OTLP_METRICS_CLIENT_KEY` is the clients private key to use in mTLS communication in PEM format.
+"""
+
+OTEL_METRICS_EXEMPLAR_FILTER = "OTEL_METRICS_EXEMPLAR_FILTER"
+"""
+.. envvar:: OTEL_METRICS_EXEMPLAR_FILTER
+
+The :envvar:`OTEL_METRICS_EXEMPLAR_FILTER` is the filter for which measurements can become Exemplars.
+"""
+
+_OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION = "OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION"
+"""
+.. envvar:: OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION
+
+The :envvar:`OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION` is the default aggregation to use for histogram instruments.
+"""
+
+OTEL_EXPORTER_OTLP_METRICS_CLIENT_CERTIFICATE = "OTEL_EXPORTER_OTLP_METRICS_CLIENT_CERTIFICATE"
+"""
+.. envvar:: OTEL_EXPORTER_OTLP_METRICS_CLIENT_CERTIFICATE
+
+The :envvar:`OTEL_EXPORTER_OTLP_METRICS_CLIENT_CERTIFICATE` is the client certificate/chain trust for clients private key to use in mTLS communication in PEM format.
+"""

Diff for: opentelemetry-sdk/src/opentelemetry/sdk/metrics/_internal/export/__init__.py

@@ -52,6 +52,10 @@
 )
 from opentelemetry.sdk.metrics._internal.point import MetricsData
 from opentelemetry.util._once import Once
+from opentelemetry.sdk.environment_variables import (
+    OTEL_METRIC_EXPORT_INTERVAL,
+    OTEL_METRIC_EXPORT_TIMEOUT
+)
 
 _logger = getLogger(__name__)
 
@@ -437,7 +441,7 @@ def __init__(
         if export_interval_millis is None:
             try:
                 export_interval_millis = float(
-                    environ.get("OTEL_METRIC_EXPORT_INTERVAL", 60000)
+                    environ.get(OTEL_METRIC_EXPORT_INTERVAL, 60000)
                 )
             except ValueError:
                 _logger.warning(
@@ -447,7 +451,7 @@ def __init__(
         if export_timeout_millis is None:
             try:
                 export_timeout_millis = float(
-                    environ.get("OTEL_METRIC_EXPORT_TIMEOUT", 30000)
+                    environ.get(OTEL_METRIC_EXPORT_TIMEOUT, 30000)
                 )
             except ValueError:
                 _logger.warning(