1 # gRPC Server Backward Compatibility Issues and Workarounds Management 2 3 ## Introduction 4 This document lists the workarounds implemented on gRPC servers for record and reference when users need to enable a certain workaround. 5 6 ## Workaround List 7 8 ### Cronet Compression 9 10 **Workaround ID:** WORKAROUND\_ID\_CRONET\_COMPRESSION 11 12 **Date added:** May 06, 2017 13 14 **Status:** Implemented in C core and C++ 15 16 **Issue:** Before version v1.3.0-dev, gRPC iOS client's Cronet transport did not implement compression. However the clients still claim to support compression. As a result, a client fails to parse received message when the message is compressed. 17 The problem above was resolved in gRPC v1.3.0-dev. For backward compatibility, a server must forcingly disable compression for gRPC clients of version lower than or equal to v1.3.0-dev. 18 19 **Workaround Description:** Implemented as a server channel filter in C core. The filter identifies the version of peer client with incoming `user-agent` header of each call. If the client's gRPC version is lower that or equal to v1.3.x, a flag GRPC_WRITE_NO_COMPRESS is marked for all send_message ops which prevents compression of the messages to be sent out. 20