gRPC-Core Release 1.15.0

[Srini Polavarapu]

This is 1.15.0(glider) release announcement for gRPC-Core and the wrapped languages C++, C#, Objective-C, Python, PHP and Ruby. Latest release notes are here.  

Core

• Document SSL portability and performance considerations. See https://github.com/grpc/grpc/blob/master/doc/ssl-performance.md .
• Simplify call arena size growth. (#16396)
• Make gRPC buildable with AIX and Solaris (no official support). (#15926)
• PF: Check connectivity state before watching. (#16306)
• Added system roots feature to load roots from OS trust store. (#16083)
• Fix c-ares compilation under windows (but doesn't yet enable windows DNS queries), and then enables address sorting on Windows. (#16163)
• Fix re-resolution in pick first. (#16076)
• Allow error strings in final_info to propagate to filters on call destruction. (#16104)
• Add resolver executor . (#16010)
• Data race fix for lockfree_event. (#16053)
• Channelz: Expose new Core API. (#16022)

C++

• cmake: disable assembly optimizations only when necessary. (#16415)
• C++ sync server: Return status RESOURCE_EXHAUSTED if no thread quota available. (#16356)
• Use correct target name for gflags-config.cmake. (#16343)
• Make should generate pkg-config file for gpr as well. (#15295)
• Restrict the number of threads in C++ sync server. (#16217)
• Allow reset of connection backoff. (#16225)

C#

• Add experimental support for Xamarin.Android and Xamarin.iOS, added Helloworld example for Xamarin. See https://github.com/grpc/grpc/tree/master/src/csharp/experimental.
• Add experimental support for Unity Android and iOS. See https://github.com/grpc/grpc/tree/master/src/csharp/experimental.
• Add server reflection tutorial. See https://github.com/grpc/grpc/blob/master/doc/csharp/server_reflection.md.
• Avoid deadlock while cancelling a call. (#16440)
• Subchannel sharing for secure channels now works as expected. (#16438)
• Allow dot in metadata keys. (#16444)
• Avoid shutdown crash on iOS. (#16308)
• Add script for creating a C# package for Unity. (#16208)
• Add Xamarin example. (#16194)
• Cleanup and update C# examples. (#16144)
• Grpc.Core: add support for x86 android emulator. (#16121)
• Xamarin iOS: Add libgrpc_csharp_ext.a for iOS into Grpc.Core nuget. (#16109)
• Xamarin support improvements . (#16099)
• Mark native callbacks with MonoPInvokeCallback. (#16094)
• Xamarin.Android: add support. (#15969)

Objective-C

• Make BoringSSL symbols private to gRPC in Obj-C so there is no conflict when linking with OpenSSL. (#16358)
• Use environment variable to enable CFStream. (#16261)
• Surface error_string to ObjC users. (#16271)
• Fix GRPCCall refcounting issue. (#16213)

Python

• Added support for client-side fork on Linux and Mac by setting the environment variable GRPC_ENABLE_FORK_SUPPORT=1. Applications may fork with active RPCs, as long as no user threads are currently invoking gRPC library methods. In-progress RPCs continue in the parent process, and the child process may use gRPC by creating new channels. (#16264)
• Improve Pypy compatibility. (#16364)
• Segmentation fault caused by channel.close() when used with connectivity-state subscriptions. (#16296)
• Add server reflection guide for Python. See https://github.com/grpc/grpc/blob/master/doc/python/server_reflection.md.
• Refresh pb2 files in examples/python/multiplex. (#16253)
• Adding python version environmental markers in the new style. (#16235)
• Add a matching _unwrap_grpc_arg. (#16197)
• Add Cython functionality to directly wrap grpc_arg. (#16192)