gruf - gRPC Ruby Framework

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gruf is a Ruby framework that wraps the gRPC Ruby library to provide a more streamlined integration into Ruby and Ruby on Rails applications.

It provides an abstracted server and client for gRPC services, along with other tools to help get gRPC services in Ruby up fast and efficiently at scale. Some of its features include:

  • Abstracted server endpoints with before, around, outer around, and after hooks during an endpoint call
  • Robust client error handling and metadata transport abilities
  • Server authentication strategy support, with basic auth with multiple key support built in
  • TLS support for client-server auth, though we recommend using linkerd instead
  • Error data serialization in output metadata to allow fine-grained error handling in the transport while still preserving gRPC BadStatus codes
  • Server and client execution timings in responses

gruf currently has active support for gRPC 1.4.x. gruf is compatible and tested with with Ruby 2.2, 2.3, and 2.4. gruf is also not Rails-specific, and can be used in any Ruby framework (such as Grape, for instance).

Installation

gem 'gruf'

Then in an initializer or before use:

require 'gruf'

Client

From there, you can instantiate a client given a stub service (say on an SslCertificates proto with a GetSslCertificate call):

require 'gruf'

id = args[:id].to_i.presence || 1

begin
  client = ::Gruf::Client.new(service: ::Demo::ThingService)
  response = client.call(:GetMyThing, id: id)
  puts response.message.inspect
rescue Gruf::Client::Error => e
  puts e.error.inspect
end

Note this returns a response object. The response object can provide trailing_metadata as well as a execution_time.

Server

Add an initializer:

require 'gruf'

Gruf.configure do |c|
  c.server_binding_url = 'grpc.service.com:9003'
end

Next, setup some handlers based on your proto configurations in /app/rpc/. For example, for the Thing service, with a GetThingReq/GetThingResp call based on this proto:

syntax = "proto3";

package demo;

service Jobs {
    rpc GetJob(GetJobReq) returns (GetJobResp) { }
}

message GetJobReq {
    uint64 id = 1;
}

message GetJobResp {
    uint64 id = 1;
    string name = 2;
}

You'd have this handler in /app/rpc/demo/job_server.rb

module Demo
  class JobServer < ::Demo::Jobs::Service
    include Gruf::Service

    ##
    # @param [Demo::GetJobReq] req The incoming gRPC request object
    # @param [GRPC::ActiveCall] call The gRPC active call instance
    # @return [Demo::GetJobResp] The job response
    #
    def get_job(req, call)
      thing = Job.find(req.id)

      Demo::GetJobResp.new(
        id: thing.id
      )
    rescue
      fail!(req, call, :not_found, :job_not_found, "Failed to find Job with ID: #{req.id}")
    end
  end
end

Finally, you can start the server by running:

bundle exec gruf

Authentication

Authentication is done via a strategy pattern and are injectable via middleware. If any of the strategies return true, it will proceed the request as successful. For example, to add basic auth, you can do:

Gruf::Authentication::Strategies.add(:basic, Gruf::Authentication::Basic)

Options to the middleware libraries can be passed through the authentication_options configuration option.

To add a custom authentication pattern, your class must extend the Gruf::Authentication::Base class, and implement the valid?(call) method. For example, this class allows everyone in:

class NoAuth < Gruf::Authentication::Base
  def valid?(_call)
    true
  end
end

Basic Auth

gruf supports simple basic authentication with an array of accepted credentials:

Gruf.configure do |c|  
  c.authentication_options = {
    credentials: [{
      username: 'my-username-here',
      password: 'my-password-here',    
    },{
      username: 'another-username',
      password: 'another-password',    
    },{
      password: 'a-password-only'
    }]
  }
end

Supporting an array of credentials allow for unique credentials per service, or for easy credential rotation with zero downtime.

SSL Configuration

We don't recommend using TLS for gRPC, but instead using something like linkerd for TLS encryption between services. If you need it, however, this library supports TLS.

For the client, you'll need to point to the public certificate:

::Gruf::Client.new(
  service: Demo::ThingService,
  ssl_certificate: 'x509 public certificate here',
  # OR
  ssl_certificate_file: '/path/to/my.crt' 
)

If you want to run a server you'll need both the CRT and the key file if you want to do credentialed auth:

Gruf.configure do |c|
  c.use_ssl = true
  c.ssl_crt_file = "#{Rails.root}/config/ssl/#{Rails.env}.crt"
  c.ssl_key_file = "#{Rails.root}/config/ssl/#{Rails.env}.key"
end

Hooks

gruf supports hooks that act as interceptors around the grpc server calls, allowing you to perform actions before, after, and even around your server endpoints. This can be used to add tracing data, connection resets in the grpc thread pool, further instrumentation, and other things.

Adding a hook is as simple as creating a class that extends Gruf::Hooks::Base, and implementing it via the registry.

Before

A before hook passes in the method call signature, request object, and GRPC::ActiveCall object:

class MyBeforeHook < Gruf::Hooks::Base
  def before(call_signature, request, active_call)
    # do my thing before the call. Calling `fail!` here will prevent the call from happening.
  end
end
Gruf::Hooks::Registry.add(:my_before_hook, MyBeforeHook)

After

An after hook passes in the response object, method call signature, request object, and GRPC::ActiveCall object:

class MyAfterHook < Gruf::Hooks::Base
  def after(success, response, call_signature, request, active_call)
    # You can modify the response object
  end
end
Gruf::Hooks::Registry.add(:my_after_hook, MyAfterHook)

Around

An around hook passes in the method call signature, request object, GRPC::ActiveCall object, and the block being executed:

class MyAroundHook < Gruf::Hooks::Base
  def around(call_signature, request, active_call, &block)
    # do my thing here 
    resp = yield
    # do my thing there
    resp
  end
end
Gruf::Hooks::Registry.add(:my_around_hook, MyAroundHook)

Around hooks are a special case - because each needs to wrap the call, they are run recursively within each other. This means that if you have three hooks - Hook1, Hook2, and Hook3 - they will run in LIFO (last in, first out) order. Hook3 will run, calling Hook2, which will then call Hook1, ending the chain.

Outer Around

And finally, an "outer" around hook passes in the method call signature, request object, GRPC::ActiveCall object, and the block being executed, and executes around the entire call chain (before, around, request, after):

class MyOuterAroundHook < Gruf::Hooks::Base
  def outer_around(call_signature, request, active_call, &block)
    # do my thing here 
    resp = yield
    # do my thing there
    resp
  end
end
Gruf::Hooks::Registry.add(:my_outer_around_hook, MyOuterAroundHook)

Outer around hooks behave similarly in execution order to around hooks.

Note: It's important to note that the authentication step happens immediately before the first before hook is called, so don't perform any actions that you want behind authentication in outer around hooks, as they are not called with authentication.

Instrumentation

gruf comes out of the box with a couple of instrumentors packed in: output metadata timings, and StatsD support.

Output Metadata Timing

Enabled by default, this will push timings for successful responses through the response output metadata back to the client.

StatsD

The StatsD support is not enabled by default. To enable it, you'll want to do:

Gruf.configure do |c|
  c.instrumentation_options = {
    statsd: {
      client: ::Statsd.new('my.statsd.host', 8125),
      prefix: 'my_application_prefix.rpc'
    }
  }
end
Gruf::Instrumentation::Registry.add(:statsd, Gruf::Instrumentation::Statsd)

This will measure counts and timings for each endpoint.

Custom Instrumentors

Similar to hooks, simply extend the Gruf::Instrumentation::Base class, and implement the call method. See the StatsD instrumentor for an example.

Plugins

You can build your own hooks and middleware for gruf; here's a list of known open source gems for gruf that you can use today:

License

Copyright (c) 2017-present, BigCommerce Pty. Ltd. All rights reserved

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.