- Author(s): muxi
- Approver: psrini
- Status: Approved
- Implemented in: Objective-C
- Last updated: 2019-07-10
- Discussion at: https://groups.google.com/forum/#!topic/grpc-io/tRKcPcfQKi4
This proposal is about global interceptor for gRPC Objective-C library.
Global interceptor refers to interceptors that run across all the calls in the same process, despite whether it is explicitly added to a particular call in its call options. It is a powerful feature for use cases such as global logging. The feature has been implemented in gRPC libraries of other languages.
- L50 - gRPC Objective-C Interceptor
The proposed gRPC Objective-C library's global interceptor interface is as follows:
@interface GRPCCall2 (Interceptor)
/**
* Register a global interceptor's factory in the current process. Only one interceptor can be
* registered in a process. If another one attempts to be registered, an exception will be raised.
*/
+ (void)registerGlobalInterceptor:(nonnull id<GRPCInterceptorFactory>)interceptorFactory;
/**
* Get the global interceptor's factory.
*/
+ (nullable id<GRPCInterceptorFactory>)globalInterceptorFactory;
@endUsers register a global interceptor with the registerGloablInterceptor method. Each process has a single global interceptor entry. The global interceptor may only be registered for once. Registering a second global interceptor will trigger an exception.
Once a global interceptor is registered, the global interceptor will be inserted at the very end of the interceptor chain of all calls in the same process.
Global interceptor is a powerful feature that resulted in abuse by some users in other gRPC libraries in the past. As a result most gRPC languages have imposed the one-global-interceptor policy. The policy helps identify the source of abusive use of global interceptor. gRPC Objective-C library follows the same rule. Making the global interceptor the last one in a chain also follows the general practice from gRPC library of other languages.
Implementation will be completed by mxyan@.