| # gRPC Server Backward Compatibility Issues and Workarounds Management |
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| ## Introduction |
| This document lists the workarounds implemented on gRPC servers for record and reference when users need to enable a certain workaround. |
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| ## Workaround List |
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| ### Cronet Compression |
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| **Workaround ID:** WORKAROUND\_ID\_CRONET\_COMPRESSION |
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| **Date added:** May 06, 2017 |
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| **Status:** Implemented in C core and C++ |
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| **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. |
| 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. |
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| **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. |
