evans VS grpcurl

Note: gRPC services can also be tested from CLI using tools like evans-cli. But for that reflection needs (if not enabled the path to the proto file is required) to be enabled in gRPC servers. This compare link shows the way to enable reflection and how to enter into evans-cli repl mode. Post entering repl mode of evans-cli, gRPC services can be tested from CLI itself and the process is described in evans-cli GitHub page.

Do you mean this one https://github.com/ktr0731/evans ?

I use Evans, it supports gRPC and gRPC-web and also supports reflection protocol.

https://github.com/ktr0731/evans it's the best cli tool I've ever used

Over the holidays, 2021, Postman gifted a fine upgrade to its users: beta support for the gRPC protocol in its API platform. As a Product Manager for Lightbend and helping out on its new gRPC native PaaS for building and running APIs and microservices, I was excited, to say the least. In another, recent blog post, I mentioned my desire to leverage UI test-and-try tools for APIs (my time in the REST API world of Mashery and PubNub was the source of such desire). In that same post though, I noted the lack of several important gRPC features, like server reflection and more robust import capabilities, as blockers; hence, my deep dive, in that post, into the CLI tool, Evans.

And who am I kidding? I'm a CLI-type person. Which is why I was super excited to stumble about Evans. Within minutes, I had gone from installation to trying out TLS-secured APIs and microservices running in the cloud on Lightbend's new serverless offering.

If everything is set up correctly, you should now be able to use evans to access your web server at the load balancer url or even the url for your ec2 instance directly e.g.

After running the server with cargo run, I needed a way to test that the server works. I had heard of an interesting tool called evans, so I decided to use this. It took me a while to figure out the right parameters to query the server, especially because tonic doesn't seem to support gRPC reflection right now, and there are few examples out there.

For testing gRPC we can use evans and need add reflection:

grpcurl

The API server will be built and start running on port 50051. You can test the functionality using a gRPC client of your choice like grpcurl or Postman.

> What is the ubiquitous utility for interacting with gRPC? We have curl for REST. What is openAPI of gRPC?

grpcurl[1] combined with gRPC server reflection[2]. The schema is compiled into the server as an encoded proto which is exposed via server reflection, which grpcurl reads to send correctly encoded requests.

[1] https://github.com/fullstorydev/grpcurl

The whole idea behind the post is that accessing the gRPC service with regular tools is impossible. To test, we need a dedicated tool nonetheless. I found grpcurl. Let's install it and use it to list available services:

gRpcurl is a cool little tool to look at btw. Had to use it at my job before. Can call a gRPC via a curl like command. Regular curl doesn't support HTTP2. Had to use TLS with some tokens even. But you can reference a local .proto(gRPC protobuf file for the call) and make things easier for yourself if you hate reading instructions on command line args like I do.

A simple GRPC client built using grpcurl.

Try testing with grpcurl, using the -H or -rpc-header flags to set the appropriate header.