When comparing GRPC vs RabbitMQ, the Slant community recommends RabbitMQ for most people. In the question“What are the best Message broker services?” RabbitMQ is ranked 1st while GRPC is ranked 2nd. The most important reason people chose RabbitMQ is:
RabbitMQ is licensed under the Mozilla Public License. Because it's such a core part of a system, it's better that it's open source to avoid expensive licensing or consulting fees.
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Pros
Pro Allows streaming
Streaming can not be done with a REST API, read Unary Streaming via gRPC.
Pro Cross platform
Pro Super fast
Pro Open Source
RabbitMQ is licensed under the Mozilla Public License. Because it's such a core part of a system, it's better that it's open source to avoid expensive licensing or consulting fees.
Pro Written in Erlang
Erlang is a fast concurrent language designed for non-stop, real time, message passing applications, which makes it a great language for a message queue.
Pro Backed by Pivotal Software
Although RabbitMQ is open source, it is still backed by Pivotal Software, giving it a stronger financial and developer backing. It also means there's a company to go to if you need help scaling in the future.
Pro Uses a Broker Architecture
Messages in RabbitMQ are sent to a central broker before being passed to clients. This makes RabbitMQ a better choice if you are in need of more complicated methods of message passing such as routing and load balancing.