gRPC-Core Release 1.16.0

[Stanley Cheung]

This is 1.16.0 (gao) release announcement for gRPC-Core and the wrapped languages C++, C#, Objective-C, Python, PHP and Ruby. Latest release notes are here.

Core

• Keepalive watchdog firing should return status UNAVAILABLE. (#16764)
• Set TCP_USER_TIMEOUT socket option for linux . (#16419)
• When using c-ares, resolve ip literals and Windows localhost on our own. (#16420)
• Turn loading system root certificate as default. (#16536)
• Change pick_first to not unref unselected subchannels. (#16342)

C++

• fix *_unsecure.pc files. (#16754)
• cmake: prevent C core from depending on libstdc++. (#16752)
• Implement Watch method in health check service. (#16574)
• Fix async_stream.h warning on Visual Studio. (#16544)

C#

• Secure channel throughput improvements: Linux x86_64 version of grpc_csharp_ext nuget now ships with assembly-optimized version of boringssl, which leads to significant improvements in throughput of secure C# channels. See https://github.com/grpc/grpc/blob/v1.16.x/doc/ssl-performance.md for details.
• Expose certificate request type in SslServerCredentials. (#16552)
• build assembly-optimized grpc_csharp_ext with cmake. (#16777)
• ChannelOption improvements. (#16756)
• Various allocation optimizations. (#16631)
• Add new C# serialization API. (#16367)
• Add constructor overload for RpcException. (#16553)
• Avoid leaking resources when starting a call fails. (#16554)
• Expose TryWaitForStateChangedAsync. (#16556)
• Add exception info to Status.Detail if metadata credentials throws. (#16543)

Objective-C

• Fixed a crash related to error reporting. (#16696)

Python

• Fix SSL channel credential when an argument is None. (#16640)
• Bazel: Fix python BUILD rules. (#16561)

Ruby

• Switch to send instead of method(...).call. (#16642)
• Rescue GRPC::Core::CallError so that worker threads are not killed. (#16477)
• support for ruby_package options. (#16014)
• ruby: Raise instead of hanging if grpc is used before and after fork. (#16332)