Enable ALPN over TLS for H2 by default (#3213)

Author: alextwoods

gems/aws-sdk-core/CHANGELOG.md

@@ -1,6 +1,8 @@
 Unreleased Changes
 ------------------
 
+* Issue - Enable ALPN over TLS for H2 by default.
+
 3.220.1 (2025-03-06)
 ------------------
 

gems/aws-sdk-core/lib/seahorse/client/plugins/h2.rb

@@ -53,10 +53,10 @@ class H2 < Plugin
 When `true`, HTTP2 debug output will be sent to the `:logger`.
         DOCS
 
-        option(:enable_alpn, default: false, doc_type: 'Boolean', docstring: <<-DOCS)
-Set to `true` to enable ALPN in HTTP2 over TLS. Requires Openssl version >= 1.0.2.
-Defaults to false. Note: not all service HTTP2 operations supports ALPN on server
-side, please refer to service documentation.
+        option(:enable_alpn, default: true, doc_type: 'Boolean', docstring: <<-DOCS)
+Set to `false` to disable ALPN in HTTP2 over TLS. ALPN requires Openssl version >= 1.0.2.
+Note: RFC7540 requires HTTP2 to use ALPN over TLS but some
+services may not fully support ALPN and require setting this to `false`.
         DOCS
 
         option(:logger)

gems/aws-sdk-core/spec/seahorse/client/plugins/h2_spec.rb

@@ -72,7 +72,7 @@ module Plugins
           end
 
           it 'adds a :enable_alpn option with default' do
-            expect(config.enable_alpn).to eq(false)
+            expect(config.enable_alpn).to eq(true)
           end
 
           it 'defaults the :raise_response_errors to true' do