GRPC - Service Code

Unlike classic HTTP and REST endpoints GRPC enforce most strict request/response format driven by .proto files declaration and compiled into binary messages using protoc compiler.

Note
Use https://github.com/spiral/app-grpc as the base to speed up onboarding.

#Define the Service

To declare our first service create a proto file in the desired direction. By default, the GRPC build proposes to create the proto files in /proto directory. Create file proto/calculator.proto:

syntax = "proto3";

option php_namespace = "App\\Calculator";
option php_metadata_namespace = "App\\GPBMetadata";

package app;

message Sum {
    int32 a = 1;
    int32 b = 2;
}

message Result {
    int32 result = 1;
}

service Calculator {
    rpc Sum (app.Sum) returns (app.Result) {
    }
}

Note
Make sure to use options php_namespace and php_metadata_namespace to properly configure PHP namespace. You can read more about GRPC service declaration here.

At the moment you can only create Unidirectional APIs.

#Generate the service

You can generate the service code manually using the protoc compiler and php-grpc plugin.

Execute the command below:

protoc -I ./proto/ --php_out=app/src --php-grpc_out=app/src proto/calculator.proto

The default protoc compiler does not respect the location of the application namespaces. The code will be generated in the app/src/App/Calculator and app/src/App/GPBMetadata directories. Move the generated code to make it loadable:

• app/src/Calculator
• app/src/GPBMetadata

#Generate Command

Put proto file into app/config/grpc.php

'services' => [
    __DIR__.'/../../proto/calculator.proto',
],

You can use the command embedded to the framework to simplify the service code generation, simply run:

php app.php grpc:generate

You should see the following output:

Compiling `proto/calculator.proto`:
• app/src/Calculator/CalculatorInterface.php
• app/src/Calculator/Result.php
• app/src/Calculator/Sum.php
• app/src/GPBMetadata/Calculator.php

The code will be moved into the proper place automatically.

#Implement Service

Implement the CalculatorInterface located in app/src/Calculator in order to make your service work:

<?php

declare(strict_types=1);

namespace App\Calculator;

use Spiral\RoadRunner\GRPC;

class Calculator implements CalculatorInterface
{
    public function Sum(GRPC\ContextInterface $ctx, Sum $in): Result
    {
        return new Result([
            'result' => $in->getB() + $in->getA()
        ]);
    }
}

Note
You can not use the method injection with GRPC services at the moment. Stick to Prototype component.

Make sure to update the proto path in .rr.yaml:

grpc:
  listen: tcp://0.0.0.0:50051
  proto: "proto/calculator.proto"

#Multiple Services

Use the import directive of proto declarations to combine multiple services in one application or store message declarations separately.

#Test the Service

You can test your service now:

./rr serve

#Metadata

Use Spiral\GRPC\ContextInterface to access the request metadata. There are number of system metadata properties you can read:

use Spiral\RoadRunner\GRPC;

public function Sum(GRPC\ContextInterface $ctx, Sum $in): Result
{
    dumprr($ctx->getValue(':authority'));
    dumprr($ctx->getValue(':peer.address'));
    dumprr($ctx->getValue(':peer.auth-type'));

    dumprr($ctx->getValue('user-agent'));
    dumprr($ctx->getValue('content-type'));

    return new Result([
        'result' => $in->getB() + $in->getA()
    ]);
}

Note
Read more about auth practices here.

#Response Headers

You can add any custom metadata to response using Context-specific response headers:

<?php

declare(strict_types=1);

namespace App\Calculator;

use Spiral\RoadRunner\GRPC;

class Calculator implements CalculatorInterface
{
    public function Sum(GRPC\ContextInterface $ctx, Sum $in): Result
    {
        /** @var GRPC\ResponseHeaders $responseHeaders */
        $responseHeaders = $ctx->getValue(GRPC\ResponseHeaders::class);
        $responseHeaders->set('key', 'value');

        return new Result([
            'result' => $in->getB() + $in->getA()
        ]);
    }
}

#Errors

spiral/roadrunner-grpc component provides a number of exceptions to indicate the server or request error:

Note
See all status codes in Spiral\RoadRunner\GRPC\StatusCode. Read more about GRPC error codes here.

#Example:

<?php

declare(strict_types=1);

namespace App\Calculator;

use Spiral\RoadRunner\GRPC;

class Calculator implements CalculatorInterface
{
    public function Sum(GRPC\ContextInterface $ctx, Sum $in): Result
    {
        if ($in->getA() < 0 || $in->getB() < 0) {
            throw new GRPC\Exception\GRPCException(
                "A and B arguments should be above zero",
                GRPC\StatusCode::INVALID_ARGUMENT
            );
        }

        return new Result([
            'result' => $in->getB() + $in->getA()
        ]);
    }
}

#Best Practices

The recommended approach of designing the GRPC API for spiral application is to generate service code interfaces, messages, and client code in a separate repository.

Common:

• Image-SDK - v1.2.0

Services:

• Image-Service - implements Image-SDK v1.2.0
• Account-Service - requires Image-SDK v1.1.0