googleapis VS grpc-web

Rich Error Model: This model enables servers to return and clients to consume additional error details expressed as one or more protobuf messages. It further specifies a standard set of error message types to cover the most common error (QuotaFailure, PreconditionFailure, BadRequest, etc). When an error occurs, the server returns the appropriate status code along with an optional error message.

They list search in their public api

https://github.com/googleapis/googleapis/blob/288aa7fb71c9b6...

We structure the repo according to proto packages. It's quite similar to how the googleapis repository is structured.

It's unfortunate that the spec doesn't contain custom fields to a sub-object like other RPC specs, like proto Status [1]. They should have had the message go into a field named "message" and not "detail". And have a field like "details" where the opaque type is serialized, which should be named by the "type" field. The problem is that systems with existing error types may have field name conflicts with type, title, status, detail, or instance, so we'd just dump the actual error into a custom "extension member" which by definition, isn't standard.

[1] https://github.com/googleapis/googleapis/blob/1c8a25ab153eef...

Protobuf (https://github.com/googleapis/googleapis)

All the required changes can be viewed in our last demo, the grpc-rest-app implementation. First, we need to update our proto service interface to help the proxy service make our gRPC service methods available at the right URLs and for the correct HTTP operations. To do this, the Google API HTTP library provides annotations we can add to our proto to describe the correct mappings. The buf tool allows us to include the googleapis dependency as a plugin in our buf.yaml file).

I think this only makes sense if the 3rd party is also throwing custom exceptions.

If you want to reduce coupling you should avoid throwing custom exceptions at all. Semantic information can go in the error message and log. The error type should be used to indicate to your program whether an error is recoverable, retriable or some other action needs to be taken. For example google on has 16 canonical error codes for all APIs.

https://github.com/googleapis/googleapis/blob/master/google/...

OpenAPI and possibly developing reusable, versioned client libraries could help, but it's a major undertaking that gRPC makes redundant. I'd be tempted to use grpc-gateway even if I had to implement a REST API. Try looking into buf and monorepo structures for proto management, e.g. something like GoogleCloudPlatform/microservices-demo. For more thorough proto and grpc-gateway definition examples, see googleapis/googleapis.

Firestone does provide global consistency, so the following quote is incorrect:

> In Cloud Firestore, the data on the client are loaded from the database at different points in time. Even if you listen for realtime updates, results from separate queries will not remain in sync. This creates consistency anomalies and bugs in your app.

Here is a link to the protocol documentation that the clients use to support it: https://github.com/googleapis/googleapis/blob/d0b394f188e8c3...

I'd link to the client implementation but it's quite involved.

Well there is Timestamp defined as a well known type which is available to all implementations despite not being a primitive type [1]. Plus one is obviously able to define any other custom types if necessary- eg as seen in [2].

[1] https://developers.google.com/protocol-buffers/docs/referenc...

[2] https://github.com/googleapis/googleapis/blob/master/google/...

* Additionally, client can stream data to the backend server (if bidirectional GRPC streams are used). I.e. client sends WebSocket messages, those will be transformed to GRPC messages by WebSocket server and delivered to the application backend.

As a result we have a system which allows to quickly create individual streams by using strict GRPC contract but terminating connections over WebSocket transport. So it works well in web browsers. After that no need to write WebSocket protocol, client implementation, handle WebSocket connection. This all will be solved by a suggested WebSocket server and its client SDKs.

The mechanics is similar to Websocketd (https://github.com/joewalnes/websocketd), but instead of creating OS processes we create GRPC streams. The difference from grpc-web (https://github.com/grpc/grpc-web) is that we provide streaming capabilities but not exposing GRPC contract to the client - just allowing to stream any data as payload (both binary and text) with some wrappers from our client SDKs side for managing subscriptions. I.e. it's not native GRPC streams on the client side - we expose just Connection/Subscription object to stream in both directions. GRPC streams used only for communication between WebSocket server and backend. To mention - grpc-web does not support all kinds of streaming now (https://github.com/grpc/grpc-web#streaming-support) while proposed solution can. This all should provide a cross-platform way to quickly write streaming apps due to client SDKs and language-agnostic nature of GRPC.

I personally see both pros and cons in this scheme (without concentrating on both too much here to keep the question short). I spent some time thinking about this myself, already have some working prototypes – but turned out need more opinions before moving forward with the idea and releasing this, kinda lost in doubts.

My main question - whether this seems interesting for someone here? Do you find this useful and see practical value?

By default, web browsers do not support gRPC, but we will use gRPC-web to make it possible.

You just have to use a library implementation for JavaScript https://github.com/grpc/grpc-web

TypeScript support remains an experimental feature of gRPC.

The gRPC-Web protocol supports HTTP/1 and can be used from a browser.

-- grpc-web

gRPC is mainly used in server-to-server communication, but it can also be used in client-to-server communication. gRPC-web is a gRPC implementation for web browsers. It is a JavaScript library that allows you to call gRPC services from a web browser. It supports Unary and Streaming Server API calls.

Since we're using Envoy, there's one more neat trick that we can employ. It turns out that Envoy also support gRPC-Web out of the box, a JavaScript client designed to support gRPC communication from the browser! That means that we can send gRPC messages over HTTP/1.1 as base64 encoded strings or as binary protobufs. Messages will be sent through our proxy and on to our backend service. The advantage of this is smaller and more efficient wire communication which should lead to better performance.

protoc-gen-grpc-web — a plugin that allows our front end to communicate with the backend using gRPC calls. A separate blog post on this coming up in the future.