Update docs for batch span processor env vars (#2485)

src/OpenTelemetry/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+* Changed `BatchExportActivityProcessorOptions` to throw `ArgumentException`
+  if it fails to parse any of the supported environment variables.
+
 ## 1.2.0-beta1
 
 Released 2021-Oct-08

src/OpenTelemetry/README.md

@@ -215,6 +215,9 @@ purposes, the SDK provides the following built-in processors:
   | `OTEL_BSP_MAX_EXPORT_BATCH_SIZE` | `MaxExportBatchSizeEnvVarKey`                  |
   <!-- markdownlint-enable MD013 -->
 
+  `ArgumentException` is thrown in case of an invalid value for any of the
+  supported environment variables.
+
 * [CompositeProcessor&lt;T&gt;](../../src/OpenTelemetry/CompositeProcessor.cs)
   : This is a processor which can be composed from multiple processors. This is
   typically used to construct multiple processing pipelines, each ending with

src/OpenTelemetry/Trace/BatchExportActivityProcessorOptions.cs

@@ -26,6 +26,10 @@ namespace OpenTelemetry.Trace
     /// OTEL_BSP_MAX_QUEUE_SIZE, OTEL_BSP_MAX_EXPORT_BATCH_SIZE, OTEL_BSP_EXPORT_TIMEOUT, OTEL_BSP_SCHEDULE_DELAY
     /// environment variables are parsed during object construction.
     /// </summary>
+    /// <remarks>
+    /// The constructor throws <see cref="ArgumentException"/> if it fails to parse
+    /// any of the supported environment variables.
+    /// </remarks>
     public class BatchExportActivityProcessorOptions : BatchExportProcessorOptions<Activity>
     {
         internal const string MaxQueueSizeEnvVarKey = "OTEL_BSP_MAX_QUEUE_SIZE";